Edgar Filing: EATON VANCE SENIOR INCOME TRUST

As filed with the Securities and Exchange Commission on October 24, 2018

1933 Act File No. 333-________

1940 Act File No. 811-09013

SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 20549

FORM N-2

	REGISTRATION STATEMENT UNDER THE SECURITIES ACT of 1933	x
	PRE-EFFECTIVE AMENDMENT NO.	¨
	POST-EFFECTIVE AMENDMENT NO.	¨
	and/or
	REGISTRATION STATEMENT UNDER THE INVESTMENT COMPANY ACT OF 1940	o
	AMENDMENT NO. 18	x

EATON VANCE SENIOR INCOME TRUST
(Exact Name of Registrant as Specified in Charter)

Two International Place, Boston, Massachusetts 02110
(Address of Principal Executive Offices)

(617) 482-8260
(Registrant’s Telephone Number)

Frederick S. Marius
Two International Place, Boston, Massachusetts 02110
(Name and Address of Agent for Service)

Approximate Date of Proposed Public Offering: As soon as practicable after the effective date of this Registration Statement.

If any of the securities being registered on this form are to be offered on a delayed or continuous basis in reliance on Rule 415 under the Securities Act of 1933, as amended, other than securities offered in connection with a dividend reinvestment plan, check the following box. x

It is proposed that this filing will become effective (check appropriate box):

¨ When declared effective pursuant to Section 8(c)

CALCULATION OF REGISTRATION FEE UNDER THE SECURITIES ACT OF 1933

Title of Securities Being Registered	Amount Being Registered⁽¹⁾	Proposed Maximum Offering Price Per Unit ⁽¹⁾	Proposed Maximum Aggregate Offering Price ⁽¹⁾	Amount of Registration Fees⁽¹⁾⁽²⁾
Common Shares $0.01 par value	1,000 Shares	$6.51	$6,510	$0.79

⁽¹⁾

Estimated solely for the purpose of calculating the registration fee in accordance with Rule 457(c) under the Securities Act of 1933, as amended, based on the average of the high and low sales prices of the Common Shares of beneficial interest on October 22, 2018 as reported on the New York Stock Exchange.

⁽²⁾

Transmitted prior to filing.

__________________________________________

The Registrant hereby amends this Registration Statement on such date or dates as may be necessary to delay its effective date until the Registrant shall file a further amendment which specifically states this Registration Statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933, as amended or until the Registration Statement shall become effective on such dates as the Commission, acting pursuant to said Section 8(a), may determine.

PRELIMINARY PROSPECTUS

SUBJECT TO COMPLETION

[_____], 2018

The information in this prospectus is not complete and may be changed. These securities may not be sold until the registration statement filed with the Securities and Exchange Commission is effective. This prospectus is not an offer to sell these securities and it is not soliciting an offer to buy these securities in any jurisdiction where the offer or sale would be prohibited.

(EATON VANCE LOGO)

Up to [________] Shares

Eaton Vance Senior Income Trust

Common Shares

Investment objective and policies. Eaton Vance Senior Income Trust (the “Trust”) is a diversified, closed-end management investment company, which commenced operations on October 30, 1998. The Trust’s investment objective is to provide a high level of current income, consistent with the preservation of capital. The Trust will seek to achieve its investment objective by investing primarily in senior, secured floating-rate loans (“Senior Loans”).

Investment Adviser. The Trust’s investment adviser is Eaton Vance Management (“Eaton Vance” or the “Adviser”). As of September 30, 2018, Eaton Vance and its affiliates managed approximately $459.8 billion of fund and separate account assets on behalf of clients, including approximately $43.9 billion in floating-rate income assets.

The Offering. The Trust may offer, from time to time, in one or more offerings (each, an “Offering”), the Trust’s common shares of beneficial interest, $0.01 par value (“Common Shares”). Common Shares may be offered at prices and on terms to be set forth in one or more supplements to this Prospectus (each, a “Prospectus Supplement”). You should read this Prospectus and the applicable Prospectus Supplement carefully before you invest in Common Shares. Common Shares may be offered directly to one or more purchasers, through agents designated from time to time by us, or to or through underwriters or dealers. The Prospectus Supplement relating to the Offering will identify any agents, underwriters or dealers involved in the offer or sale of Common Shares, and will set forth any applicable offering price, sales load, fee, commission or discount arrangement between the Trust and its agents or underwriters, or among its underwriters, or the basis upon which such amount may be calculated, net proceeds and use of proceeds, and the terms of any sale. The Trust may not sell any Common Shares through agents, underwriters or dealers without delivery of a Prospectus Supplement describing the method and terms of the particular Offering of the Common Shares. (continued on inside cover page)

The Common Shares have traded both at a premium and a discount to net asset value (“NAV”). The Trust cannot predict whether Common Shares will trade in the future at a premium or discount to NAV. The provisions of the Investment Company Act of 1940, as amended (the “1940 Act”) generally require that the public offering price of common shares (less any underwriting commissions and discounts) must equal or exceed the NAV per share of a company’s common stock (calculated within 48 hours of pricing). The Trust’s issuance of Common Shares may have an adverse effect on prices in the secondary market for the Trust’s Common Shares by increasing the number of Common Shares available, which may put downward pressure on the market price for the Trust’s Common Shares. Shares of common stock of closed-end investment companies frequently trade at a discount from NAV, which may increase investors’ risk of loss.

Investing in shares involves certain risks, including that the Trust will invest substantial portions of its assets in below investment grade quality securities with speculative characteristics. See “Investment Objective, Policies and Risks” beginning at page 20.

Neither the Securities and Exchange Commission (“SEC”) nor any state securities commission has approved or disapproved of these securities or determined if this Prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

(continued from previous page)

Portfolio contents. The Trust will pursue its objective by investing its assets primarily in Senior Loans. Under normal market conditions, the Trust will invest at least 80% of its total assets in Senior Loans of domestic and foreign borrowers that are denominated in U.S. dollars, euros, British pounds, Swiss francs, Canadian dollars and Australian dollars (each, an “Authorized Foreign Currency”) making payments in such Authorized Foreign Currency. For the purposes of the 80% test, total assets is defined as net assets plus any borrowings for investment purposes, including any outstanding preferred shares. Senior Loans are made to corporations, partnerships and other business entities (“Borrowers”) that operate in various industries and geographical regions, including foreign Borrowers. Senior Loans pay interest at rates that are reset periodically on the basis of a floating base lending rate plus a premium. Senior Loans typically are of below investment grade quality and have below investment grade credit ratings, which ratings are associated with securities having high risk, speculative characteristics (sometimes referred to as “junk”).

Leverage. The Trust currently uses leverage created by issuing Auction Preferred Shares (“APS”) as well as by loans acquired with borrowings. On June 27, 2001, the Trust issued 2,200 Series A APS and 2,200 Series B APS, with a liquidation preference per share of $25,000 plus accumulated but unpaid dividends. On September 23, 2016, the Trust repurchased 968 Series A APS and 968 Series B APS. On September 14, 2018, the Trust repurchased 480 Series A APS and 480 Series B APS. In addition, in connection with this repurchase, the Trust increased its borrowing limits under its Revolving Credit and Security Agreement, as amended (the “Agreement”) with conduit lenders and a bank to allow it to borrow up to $125 million ($100 million prior to September 13, 2018). The proceeds of which were used to invest in accordance with the Trust’s investment practices and to partially redeem the Trust’s APS. The Trust is required to maintain certain net asset levels during the term of the Agreement. As of September 30, 2018, the Trust had $113 million in outstanding borrowings, at an interest rate of 2.21%, in addition to outstanding APS.

The Adviser anticipates that the use of leverage (from the issuance of APS and borrowings) will result in higher income to holders of Common Shares (“Common Shareholders”) over time. Use of financial leverage creates an opportunity for increased income but, at the same time, creates special risks. There can be no assurance that a leveraging strategy will be successful. The fee paid to Eaton Vance will be calculated on the basis of the Trust’s gross assets, including proceeds from the issuance of APS and borrowings, so the fees will be higher when leverage is utilized. In this regard, holders of debt or preferred securities do not bear the investment advisory fee. Rather, Common Shareholders bear the portion of the investment advisory fee attributable to the assets purchased with the proceeds, which means that Common Shareholders effectively bear the entire advisory fee. See “Investment Objective, Policies and Risks - Use of Leverage and Related Risks” at page 31, “Investment Objective, Policies and Risks - Additional Risk Considerations” at page 34 and “Description of Capital Structure” at page 43.

Exchange listing. As of [_____], 2018, the Trust had [_______] Common Shares outstanding as well as 1,504 APS outstanding. The Trust’s Common Shares are listed on the New York Stock Exchange (“NYSE”) under the symbol “EVF.” As of [_______], 2018, the last reported sale price of a Common Share of the Trust on the NYSE was $[__]. Common Shares offered and sold pursuant to this Registration Statement will also be listed on the NYSE and trade under this symbol.

This Prospectus, together with any applicable Prospectus Supplement, sets forth concisely information you should know before investing in the shares of the Trust. Please read and retain this Prospectus for future reference. A Statement of Additional Information dated [_________], 2018, has been filed with the SEC. The Statement of Additional Information, annual and semi-annual reports to shareholders when available and other information about the Trust can be obtained without charge by calling 1-800-262-1122 or by writing to the Trust at the address below or from the Trust’s website (http://www.eatonvance.com). A table of contents to the Statement of Additional Information is located at page 48 of this Prospectus. This Prospectus incorporates by reference the entire Statement of Additional Information. The Statement of Additional Information is available along with other Trust-related materials: at the SEC's public reference room in Washington, DC (call 1-202-551-8090 for information on the operation of the public reference room); the EDGAR database on the SEC's internet site (http://www.sec.gov); upon payment of copying fees by writing to the SEC's Public Reference Section, 100 F Street, NE, Washington, DC 20549-1520; or by electronic mail at publicinfo@sec.gov. The Trust’s principal office is located at Two International Place, Boston, MA 02110, and its telephone number is 1-800-262-1122.

The Trust's shares do not represent a deposit or obligation of, and are not guaranteed or endorsed by, any bank or other insured depository institution, and are not federally insured by the Federal Deposit Insurance Corporation, the Federal Reserve Board or any other government agency.

You should rely only on the information contained or incorporated by reference in this Prospectus. The Trust has not authorized anyone to provide you with different information. The Trust is not making an offer of these securities in any jurisdiction where the offer is not permitted. You should not assume that the information contained in this Prospectus is accurate as of any date other than the date on the front of this Prospectus.

Eaton Vance Senior Income Trust

Prospectus dated [____], 2018

Table of Contents

Prospectus Summary	5
Summary of Trust Expenses	15
Financial Highlights and Investment Performance	16
The Trust	19
Use of Proceeds	19
Portfolio Composition	19
Investment Objective, Policies and Risks	19
Management of the Trust	39
Plan of Distribution	40
Distributions	41
Federal Income Tax Matters	41
Dividend Reinvestment Plan	43
Description of Capital Structure	44
Custodian and Transfer Agent	47
Legal Opinions	47
Reports to Shareholders	47
Independent Registered Public Accounting Firm	47
Additional Information	47
Table of Contents for the Statement of Additional Information	48
The Trust's Privacy Policy	49

Eaton Vance Senior Income Trust

Prospectus dated [____], 2018

CAUTIONARY NOTICE REGARDING FORWARD-LOOKING STATEMENTS

This Prospectus, any accompanying Prospectus Supplement and the Statement of Additional Information contain “forward-looking statements.” Forward-looking statements can be identified by the words “may,” “will,” “intend,” “expect,” “estimate,” “continue,” “plan,” “anticipate,” and similar terms and the negative of such terms. Such forward-looking statements may be contained in this Prospectus as well as in any accompanying Prospectus Supplement. By their nature, all forward-looking statements involve risks and uncertainties, and actual results could differ materially from those contemplated by the forward-looking statements. Several factors that could materially affect our actual results are the performance of the portfolio of securities we hold, the price at which our shares will trade in the public markets and other factors discussed in our periodic filings with the SEC.

Although we believe that the expectations expressed in our forward-looking statements are reasonable, actual results could differ materially from those projected or assumed in our forward-looking statements. Our future financial condition and results of operations, as well as any forward-looking statements, are subject to change and are subject to inherent risks and uncertainties, such as those disclosed in the “Investment Objective, Policies and Risks” section of this Prospectus. All forward-looking statements contained or incorporated by reference in this Prospectus or any accompanying Prospectus Supplement are made as of the date of this Prospectus or the accompanying Prospectus Supplement, as the case may be. Except for our ongoing obligations under the federal securities laws, we do not intend, and we undertake no obligation, to update any forward-looking statement. The forward-looking statements contained in this Prospectus, any accompanying Prospectus Supplement and the Statement of Additional Information are excluded from the safe harbor protection provided by section 27A of the Securities Act of 1933, as amended (the “1933 Act”).

Currently known risk factors that could cause actual results to differ materially from our expectations include, but are not limited to, the factors described in the “Investment Objective, Policies and Risks” section of this Prospectus. We urge you to review carefully that section for a more detailed discussion of the risks of an investment in our securities.

Prospectus dated [__________], 2018

Eaton Vance Senior Income Trust

Prospectus dated [____], 2018

Prospectus Summary

The following summary is qualified in its entirety by reference to the more detailed information included elsewhere in this Prospectus, in any related Prospectus Supplement, and in the Statement of Additional Information.

THE TRUST

Eaton Vance Senior Income Trust (the “Trust”) is a diversified, closed-end management investment company, which commenced operations on October 30, 1998. The Trust offers investors the opportunity to receive a high level of current income, through a professionally managed portfolio investing primarily in senior, secured floating-rate loans (“Senior Loans”), which are normally accessible only to financial institutions and large corporate and institutional investors, and are not widely available to individual investors. To the extent consistent with this objective, the Trust may also offer an opportunity for preservation of capital. Investments are based on Eaton Vance Management's (“Eaton Vance” or the “Adviser”) internal research and ongoing credit analysis, which is generally not available to individual investors. An investment in the Trust may not be appropriate for all investors. There is no assurance that the Trust will achieve its investment objective.

THE OFFERING

The Trust may offer, from time to time, in one or more offerings (each, an “Offering”), up to [________] of the Trust’s common shares of beneficial interest, $0.01 par value (“Common Shares”), on terms to be determined at the time of the Offering. The Common Shares may be offered at prices and on terms to be set forth in one or more prospectus supplements. You should read this Prospectus and the applicable Prospectus Supplement carefully before you invest in Common Shares. Common Shares may be offered directly to one or more purchasers, through agents designated from time to time by the Trust, or to or through underwriters or dealers. The Prospectus Supplement relating to the Offering will identify any agents, underwriters or dealers involved in the offer or sale of Common Shares, and will set forth any applicable offering price, sales load, fee, commission or discount arrangement between the Trust and its agents or underwriters, or among its underwriters, or the basis upon which such amount may be calculated, net proceeds and use of proceeds, and the terms of any sale. See “Plan of Distribution.” The Trust may not sell any of Common Shares through agents, underwriters or dealers without delivery of a Prospectus Supplement describing the method and terms of the particular Offering of Common Shares.

INVESTMENT OBJECTIVE, POLICIES AND RISKS

The Trust's investment objective is to provide a high level of current income, consistent with the preservation of capital. The Trust pursues its objective by investing primarily in Senior Loans. Senior Loans are loans in which the interest rate paid fluctuates based on a reference rate. Senior Loans are made to corporations, partnerships and other business entities (“Borrowers”) that operate in various industries and geographical regions. Senior Loans pay interest at rates that are reset periodically by reference to a base lending rate, primarily the London Interbank Offered Rate (“LIBOR”), plus a premium. Under normal market conditions, at least 80% of the Trust's total assets will be invested in interests in Senior Loans. The remaining investment assets of the Trust may include, among other types of investments, equity securities that are acquired in connection with an investment in a Senior Loan of domestic and foreign borrowers that are denominated in U.S. dollars, euros, British pounds, Swiss francs, Canadian dollars and Australian dollars (each an “Authorized Foreign Currency”) making payments in such Authorized Foreign Currency. For the purpose of the 80% test, total assets is defined as net assets plus any borrowings for investment purposes, including any outstanding preferred shares. The Trust may also invest up to 15% of its net assets in foreign Senior Loans denominated in an Authorized Foreign Currency. For all foreign Senior Loan investments denominated in an Authorized Foreign Currency, the Adviser currently intends to hedge against foreign currency fluctuations through the use of currency exchange contracts and other appropriate permitted hedging strategies. It is anticipated that the proceeds of the Senior Loans in which the Trust will acquire interests primarily will be used to finance leveraged buyouts, recapitalizations, mergers, acquisitions, stock repurchases, refinancing, and to finance internal growth and for other corporate purposes of Borrowers.

The Trust may invest up to 20% of its total assets in (i) loan interests which have (a) a second lien on collateral (“Second Lien”), (b) no security interest in the collateral, or (c) lower than a senior claim on collateral; (ii) other income-producing securities, such as investment and non-investment grade corporate debt securities and U.S. government and U.S. dollar-denominated foreign government or supranational debt securities; and (iii) warrants and equity securities issued by a Borrower or its affiliates as part of a package of investments in the Borrower or its affiliates. Corporate bonds of below investment grade quality (“Non-Investment Grade Bonds”), commonly referred to as “junk bonds,” which are bonds that are rated below investment grade by each of the nationally recognized statistical rating agencies (“Rating Agencies”) who cover the security, or, if unrated, are determined to be of comparable quality by the Adviser. S&P Global Ratings (“S&P”) and Fitch Ratings (“Fitch”) consider securities rated below BBB- to be below investment grade and Moody’s Investors Service, Inc. (“Moody’s”) considers securities rated below Baa3 to be below investment grade. The Trust’s credit quality policies apply only at the time a security is purchased, and the Trust is not required to dispose of a security in the event of a downgrade of an assessment of credit quality or the withdrawal of a rating. Securities rated in the lowest investment

Eaton Vance Senior Income Trust

Prospectus dated [____], 2018

grade rating (BBB- or Baa3) may have certain speculative characteristics. Below investment grade quality securities are considered to be predominantly speculative because of the credit risk of the issuers. See “Investment Objective, Policies and Risks - Risk Considerations - Non-Investment Grade Bonds Risk.”

Investing in loans involves investment risk. Some Borrowers default on their loan payments. The Trust attempts to manage this credit risk through portfolio diversification and ongoing analysis and monitoring of Borrowers. The Trust also is subject to market, liquidity, interest rate and other risks. See “Investment Objective, Policies and Risks.”

Scott H. Page and John Redding are portfolio managers of the Trust. Mr. Page is a Vice President of Eaton Vance, is Co-Director of Eaton Vance’s Floating-Rate Loan Group and has been a portfolio manager of the Trust since October 1998. Mr. Redding is a Vice President of Eaton Vance and has been portfolio manager of the Trust since November 2001.

The Trust’s investments are actively managed, and Senior Loans and other securities may be bought or sold on a daily basis. The Adviser’s staff monitors the credit quality and price of Senior Loans and other securities held by the Trust, as well as other securities that are available to the Trust. The Trust may invest in individual Senior Loans and other securities of any credit quality. Although the Adviser considers ratings when making investment decisions, it generally performs its own credit and investment analysis and does not rely primarily on the ratings assigned by the Rating Agencies. In evaluating the quality of particular Senior Loans or other securities, whether rated or unrated, the Adviser will normally take into consideration, among other things, the issuer’s financial resources and operating history, its sensitivity to economic conditions and trends, the ability of its management, its debt maturity schedules and borrowing requirements, and relative values based on anticipated cash flow, interest and asset coverage, and earnings prospects.

The Trust may invest up to 15% of net assets in Senior Loans denominated in Authorized Foreign Currencies and may invest in other securities of non-United States issuers. The Trust’s investments may have significant exposure to certain sectors of the economy and thus may react differently to political or economic developments than the market as a whole. The Trust may accept equity securities in connection with a debt restructuring or reorganization of a Borrower either inside or outside of bankruptcy. The Trust may hold equity securities issued in exchange for a Senior Loan or issued in connection with the debt restructuring or reorganization of a Borrower. The Trust may also acquire additional equity securities of such Borrower or its affiliates if, in the judgment of the Adviser, such an investment may enhance the value of a Senior Loan held or would otherwise be consistent with the Trust’s investment policies. The Trust will not invest more than 10% of its assets in securities (including interests in Senior Loans) of any single Borrower.

The Trust may purchase or sell derivative instruments (which derive their value from another instrument, security or index) for risk management purposes, such as hedging against fluctuations in Senior Loans and other securities prices or interest rates. Transactions in derivative instruments may include the purchase or sale of futures contracts on securities, indices and other financial instruments, credit-linked notes, tranches of collateralized loan obligations and/or collateralized debt obligations, options on futures contracts, and exchange-traded and over-the-counter options on securities or indices, and interest rate, total return and credit default swaps. Guidelines of any rating organization that rates any preferred shares issued by the Trust may limit the Trust’s ability to engage in such transactions. Subject to the Trust’s policy of investing at least 80% of its total assets in Senior Loans and subject to the thresholds on the use of futures contracts and related options imposed by Rule 4.5 under the Commodity Exchange Act, as amended (the “CEA”) as promulgated by the Commodity Futures Trading Commission (“CFTC”), the Trust may invest, without limitation, in the foregoing derivative instruments for the purposes stated herein.

LISTING

As of [_______], 2018, the Trust had [_________] Common Shares outstanding as well as 1,504 APS outstanding. The Trust’s Common Shares are traded on the New York Stock Exchange (“NYSE”) under the symbol “EVF.” As of [_______], 2018, the last reported sales price of a Common Share of the Trust on the NYSE was $[_____]. Common Shares offered and sold pursuant to this Registration Statement will also be listed on the NYSE and trade under this symbol.

LEVERAGE

Eaton Vance Senior Income Trust

Prospectus dated [____], 2018

the assets of the Trust. Interest is charged at a rate above the conduits’ commercial paper issuance rate and is payable monthly. Under the terms of the Agreement, in effect through March 11, 2019, the Trust also pays a program fee of 0.67% per annum on its outstanding borrowings to administer the facility and a liquidity fee of 0.15% (0.25% if the outstanding loan amount is less than or equal to 60% of the total facility size) per annum on the borrowing limit under the Agreement. Program and liquidity fees for the year ended June 30, 2018 totaled $739,164 and for the three months ended September 30, 2018 totaled $197,384. In connection with the increase in the borrowing limit on September 13, 2018, the Trust paid an additional upfront fee of $12,260 which is being amortized over the remaining term of the Agreement to March 11, 2019. In connection with the renewal of the Agreement in March 2018, the Trust paid an upfront fee of $100,000 that is being amortized to interest expense over a period of one year through March 2019. The Trust is required to maintain certain net asset levels during the term of the Agreement. As of September 30, 2018, the Trust had $113 million in outstanding borrowings, at an interest rate of 2.21%, in addition to outstanding APS. The Adviser anticipates that the use of leverage (from such issuance of APS and borrowings) may result in higher income to holders of Common Shares (“Common Shareholders”) over time. Use of financial leverage creates an opportunity for increased income but, at the same time, creates special risks. There can be no assurance that a leveraging strategy will be successful.

The costs of the financial leverage program (from any issuance of preferred shares and any borrowings) are borne by Common Shareholders and consequently result in a reduction of the NAV of Common Shares. During periods in which the Trust is using leverage, the fees paid to Eaton Vance for investment advisory services will be higher than if the Trust did not use leverage because the fees paid will be calculated on the basis of the Trust’s gross assets, which include proceeds from the issuance of preferred shares and any borrowings. In this regard, holders of debt or preferred securities do not bear the investment advisory fee. Rather, Common Shareholders bear the portion of the investment advisory fee attributable to the assets purchased with the proceeds, which means that Common Shareholders effectively bear the entire advisory fee. See “Investment Objective, Policies and Risks - Use of Leverage and Related Risks” and “Management of the Trust - The Adviser.”

Financial leverage may also be achieved through the purchase of certain derivative instruments. The Trust’s use of derivative instruments exposes the Trust to special risks. See “Investment Objective, Policies and Risks - Additional Investment Practices” and “Investment Objective, Policies and Risks - Additional Risk Considerations.”

INVESTMENT ADVISER AND ADMINISTRATOR

Eaton Vance, a wholly-owned subsidiary of Eaton Vance Corp., is the Trust's investment adviser and administrator. As of September 30, 2018, Eaton Vance and its affiliates managed approximately $459.8 billion of fund and separate account assets on behalf of clients, including approximately $43.9 billion in floating-rate income assets. See “Management of the Trust.”

PLAN OF DISTRIBUTION

The Trust may sell the Common Shares being offered under this Prospectus in any one or more of the following ways: (i) directly to purchasers; (ii) through agents; (iii) to or through underwriters; or (iv) through dealers. The Prospectus Supplement relating to the Offering will identify any agents, underwriters or dealers involved in the offer or sale of Common Shares, and will set forth any applicable offering price, sales load, fee, commission or discount arrangement between the Trust and its agents or underwriters, or among its underwriters, or the basis upon which such amount may be calculated, net proceeds and use of proceeds, and the terms of any sale.

The Trust may distribute Common Shares from time to time in one or more transactions at: (i) a fixed price or prices that may be changed; (ii) market prices prevailing at the time of sale; (iii) prices related to prevailing market prices; or (iv) negotiated prices; provided, however, that in each case the offering price per Common Share (less any underwriting commission or discount) must equal or exceed the NAV per Common Share.

The Trust from time to time may offer its Common Shares through or to certain broker-dealers, including [_________], that have entered into selected dealer agreements relating to at-the-market offerings.

The Trust may directly solicit offers to purchase Common Shares, or the Trust may designate agents to solicit such offers. The Trust will, in a Prospectus Supplement relating to such Offering, name any agent that could be viewed as an underwriter under the 1933 Act, and describe any commissions the Trust must pay to such agent(s). Any such agent will be acting on a reasonable best efforts basis for the period of its appointment or, if indicated in the applicable Prospectus Supplement or other offering materials, on a firm commitment basis. Agents, dealers and underwriters may be customers of, engage in transactions with, or perform services for the Trust in the ordinary course of business.

If any underwriters or agents are used in the sale of Common Shares in respect of which this Prospectus is delivered, the Trust will enter into an underwriting agreement or other agreement with them at the time of sale to them, and the Trust will set forth in the Prospectus Supplement relating to such Offering their names and the terms of the Trust’s agreement with them.

Eaton Vance Senior Income Trust

Prospectus dated [____], 2018

If a dealer is utilized in the sale of Common Shares in respect of which this Prospectus is delivered, the Trust will sell such Common Shares to the dealer, as principal. The dealer may then resell such Common Shares to the public at varying prices to be determined by such dealer at the time of resale.

The Trust may engage in at-the-market offerings to or through a market maker or into an existing trading market, on an exchange or otherwise, in accordance with Rule 415(a)(4) under the 1933 Act. An at-the-market offering may be through an underwriter or underwriters acting as principal or agent for the Trust.

Agents, underwriters and dealers may be entitled under agreements which they may enter into with the Trust to indemnification by the Trust against certain civil liabilities, including liabilities under the 1933 Act, and may be customers of, engage in transactions with or perform services for the Trust in the ordinary course of business.

In order to facilitate the Offering of Common Shares, any underwriters may engage in transactions that stabilize, maintain or otherwise affect the price of Common Shares or any other Common Shares the prices of which may be used to determine payments on the Common Shares. Specifically, any underwriters may over-allot in connection with the Offering, creating a short position for their own accounts. In addition, to cover over-allotments or to stabilize the price of Common Shares or of any such other Common Shares, the underwriters may bid for, and purchase, Common Shares or any such other Common Shares in the open market. Finally, in any Offering of Common Shares through a syndicate of underwriters, the underwriting syndicate may reclaim selling concessions allowed to an underwriter or a dealer for distributing Common Shares in the Offering if the syndicate repurchases previously distributed Common Shares in transactions to cover syndicate short positions, in stabilization transactions or otherwise. Any of these activities may stabilize or maintain the market price of Common Shares above independent market levels. Any such underwriters are not required to engage in these activities and may end any of these activities at any time.

The Trust may enter into derivative transactions with third parties, or sell Common Shares not covered by this Prospectus to third parties in privately negotiated transactions. If the applicable Prospectus Supplement indicates, in connection with those derivatives, the third parties may sell Common Shares covered by this Prospectus and the applicable Prospectus Supplement or other offering materials, including in short sale transactions. If so, the third parties may use Common Shares pledged by the Trust or borrowed from the Trust or others to settle those sales or to close out any related open borrowings of securities, and may use Common Shares received from the Trust in settlement of those derivatives to close out any related open borrowings of securities. The third parties in such sale transactions will be underwriters and, if not identified in this Prospectus, will be identified in the applicable Prospectus Supplement or other offering materials (or a post-effective amendment).

The maximum amount of compensation to be received by any member of the Financial Industry Regulatory Authority, Inc. will not exceed 8% of the initial gross proceeds from the sale of any security being sold with respect to each particular Offering of Common Shares made under a single Prospectus Supplement.

Any underwriter, agent or dealer utilized in the initial Offering of Common Shares will not confirm sales to accounts over which it exercises discretionary authority without the prior specific written approval of its customer.

DISTRIBUTIONS

The Trust intends to make monthly distributions of net investment income to Common Shareholders, after payment of any dividends on any outstanding APS. The amount of each monthly distribution will vary depending on a number of factors, including dividends payable on the Trust's preferred shares or other costs of financial leverage. As portfolio and market conditions change, the rate of dividends on the Common Shares and the Trust's dividend policy could change. Over time, the Trust will distribute all of its net investment income (after it pays accrued dividends on any outstanding preferred shares) or other costs of financial leverage. In addition, at least annually, the Trust intends to distribute all or substantially all of its net realized capital gains (reduced by available capital loss carryforwards from prior years, if any). Distributions to Common Shareholders are recorded on the ex-dividend date. Distributions to preferred shareholders are recorded daily and are payable at the end of each dividend period.

Beginning February 13, 2008 and consistent with the patterns in the broader market for auction-rate securities, the Trust’s APS auctions were unsuccessful in clearing due to an imbalance of sell orders over bids to buy the APS. As a result, the dividend rates of the APS were reset to the maximum applicable rates.

The Trust distinguishes between distributions on a tax basis and a financial reporting basis. Accounting principles generally accepted in the United States of America require that only distributions in excess of tax basis earnings and profits be reported in the financial statements as a return of capital. Permanent differences between book and tax accounting relating to distributions are reclassified to paid-in capital. For tax purposes, distributions from short-term capital gains are considered to be from ordinary income.

Eaton Vance Senior Income Trust

Prospectus dated [____], 2018

Common Shareholders will automatically have distributions reinvested in additional Common Shares under the Trust's dividend reinvestment plan unless they elect otherwise through their investment dealer. See “Distributions” and “Dividend Reinvestment Plan.”

DIVIDEND REINVESTMENT PLAN

The Trust has established a dividend reinvestment plan (the “Plan”). Under the Plan, unless a Common Shareholder elects to receive distributions in cash, all distributions will be automatically reinvested in additional Common Shares. American Stock Transfer & Trust Company, LLC (“AST” or the “Plan Agent”) serves as agent for the Common Shareholders in administering the Plan. Common Shareholders who elect not to participate in the Plan will receive all Trust distributions in cash paid by check mailed directly to the Common Shareholder of record (or, if the Common Shares are held in street or other nominee name, then to the nominee) by AST, as disbursing agent. Participation in the Plan is completely voluntary and may be terminated or resumed at any time without penalty by written notice if received by the Plan Agent prior to any distribution record date. See “Dividend Reinvestment Plan.”

CLOSED-END STRUCTURE

Closed-end funds differ from open-end management investment companies (commonly referred to as mutual funds) in that closed-end funds generally list their shares for trading on a securities exchange and do not redeem their shares at the option of the shareholder. By comparison, mutual funds issue securities redeemable at NAV at the option of the shareholder and typically engage in a continuous offering of their shares. Mutual funds are subject to continuous asset in-flows and out-flows that can complicate portfolio management, whereas closed-end funds generally can stay more fully invested in securities consistent with the closed-end fund's investment objective(s) and policies. In addition, in comparison to open-end funds, closed-end funds have greater flexibility in the employment of financial leverage and in the ability to make certain types of investments, including investments in illiquid securities.

However, shares of closed-end funds frequently trade at a discount from their net asset value. Since inception, the market price of the Common Shares has fluctuated and at times traded below the Trust’s NAV, and at times has traded above NAV. In recognition of the possibility that the Common Shares might trade at a discount to net asset value and that any such discount may not be in the interest of Common Shareholders, the Trust's Board of Trustees (the “Board”), in consultation with Eaton Vance, from time to time may review possible actions to reduce any such discount. The Board might consider open market repurchases or tender offers for Common Shares at net asset value. There can be no assurance that the Board will decide to undertake any of these actions or that, if undertaken, such actions would result in the Common Shares trading at a price equal to or close to net asset value per Common Share. The Board might also consider the conversion of the Trust to an open-end management investment company. The Board believes, however, that the closed-end structure is desirable, given the Trust's investment objective and policies. Investors should assume, therefore, that it is highly unlikely that the Board would vote to convert the Trust to an open-end management investment company. Investors should note that the Trust’s preferred shares could make a conversion to open-end form more difficult because of the voting rights of preferred shareholders, the costs of redeeming preferred shares and other factors. See “Description of Capital Structure.”

SPECIAL RISK CONSIDERATIONS

Risk is inherent in all investing. Investing in any investment company security involves risk, including the risk that you may receive little or no return on your investment or even that you may lose part or all of your investment.

Discount From or Premium to NAV. The Offering will be conducted only when Common Shares of the Trust are trading at a price equal to or above the Trust’s NAV per Common Share plus the per Common Share amount of commissions. As with any security, the market value of the Common Shares may increase or decrease from the amount initially paid for the Common Shares. The Trust’s Common Shares have traded both at a premium and at a discount relative to net asset value. The shares of closed-end management investment companies frequently trade at a discount from their NAV. This is a risk separate and distinct from the risk that the Trust’s NAV may decrease.

Secondary Market for the Common Shares. The issuance of Common Shares through the Offering may have an adverse effect on the secondary market for the Common Shares. The increase in the amount of the Trust’s outstanding Common Shares resulting from the Offering may put downward pressure on the market price for the Common Shares of the Trust. Common Shares will not be issued pursuant to the Offering at any time when Common Shares are trading at a price lower than a price equal to the Trust’s NAV per Common Share plus the per Common Share amount of commissions.

The Trust also issues Common Shares of the Trust through its dividend reinvestment plan. See “Dividend Reinvestment Plan.” Common Shares may be issued under the plan at a discount to the market price for such Common Shares, which may put downward pressure on the market price for Common Shares of the Trust.

Eaton Vance Senior Income Trust

Prospectus dated [____], 2018

When the Common Shares are trading at a premium, the Trust may also issue Common Shares of the Trust that are sold through transactions effected on the NYSE. The increase in the amount of the Trust’s outstanding Common Shares resulting from that offering may also put downward pressure on the market price for the Common Shares of the Trust.

The voting power of current shareholders will be diluted to the extent that such shareholders do not purchase shares in any future Common Share offerings or do not purchase sufficient shares to maintain their percentage interest. In addition, if the Adviser is unable to invest the proceeds of such offering as intended, the Trust’s per share distribution may decrease (or may consist of return of capital) and the Trust may not participate in market advances to the same extent as if such proceeds were fully invested as planned.

Income Risk. The income investors receive from the Trust is based primarily on the interest it earns from its investments, which can vary widely over the short and long-term. If prevailing market interest rates drop, investors’ income from the Trust could drop as well. The Trust’s income could also be affected adversely when prevailing short-term interest rates increase and the Trust is utilizing leverage, although this risk is mitigated by the Trust’s investment in Senior Loans, which pay floating-rates of interest.

Market Risk. The value of investments held by the Trust may increase or decrease in response to economic, political and financial events (whether real, expected or perceived) in the U.S. and global markets. The frequency and magnitude of such changes in value cannot be predicted. Certain securities and other investments held by the Trust may experience increased volatility, illiquidity, or other potentially adverse effects in reaction to changing market conditions. Actions taken by the U.S. Federal Reserve or foreign central banks to stimulate or stabilize economic growth, such as decreases or increases in short-term interest rates, could cause high volatility in markets. No active trading market may exist for certain investments, which may impair the ability of the Trust to sell or to realize the current valuation of such investments in the event of the need to liquidate such assets. Fixed-income markets may experience periods of relatively high volatility in an environment where U.S. treasury yields are rising.

Senior Loans Risk. The risks associated with Senior Loans are similar to the risks of Non-Investment Grade Bonds (discussed below), although Senior Loans are typically senior and secured in contrast to Non-Investment Grade Bonds, which are often subordinated and unsecured. Senior Loans’ higher standing has historically resulted in generally higher recoveries in the event of a corporate reorganization or other restructuring. In addition, because their interest rates are adjusted for changes in short-term interest rates, Senior Loans generally have less interest rate risk than Non-Investment Grade Bonds, which are typically fixed rate. The Trust’s investments in Senior Loans are typically below investment grade and are considered speculative because of the credit risk of their issuers. Such companies are more likely to default on their payments of interest and principal owed to the Trust, and such defaults could reduce the Trust’s net asset value and income distributions. An economic downturn generally leads to a higher non-payment rate, and a debt obligation may lose significant value before a default occurs. Moreover, any specific collateral used to secure a loan may decline in value or lose all its value or become illiquid, which would adversely affect the loan’s value. “Junior Loans” are secured and unsecured subordinated loans, second lien loans and subordinate bridge loans. Senior Loans and Junior Loans are referred to together herein as “loans.”

Loans and other debt securities are also subject to the risk of price declines and to increases in prevailing interest rates, although floating-rate debt instruments are less exposed to this risk than fixed-rate debt instruments. Interest rate changes may also increase prepayments of debt obligations and require the Trust to invest assets at lower yields.

Loans are traded in a private, unregulated inter-dealer or inter-bank resale market and are generally subject to contractual restrictions that must be satisfied before a loan can be bought or sold. These restrictions may impede the Trust’s ability to buy or sell loans (thus affecting their liquidity) and may negatively impact the transaction price. See also “Market Risk” above. It also may take longer than seven days for transactions in loans to settle. Due to the possibility of an extended loan settlement process, the Trust may hold cash, sell investments or temporarily borrow from banks or other lenders to meet short-term liquidity needs. Loans may be structured such that they are not securities under securities law, and in the event of fraud or misrepresentation by a borrower, lenders may not have the protection of the anti-fraud provisions of the federal securities laws. Loans are also subject to risks associated with other types of income investments as described herein.

Credit Risk. Investments in loans and other debt obligations (referred to below as “debt instruments”) are subject to the risk of non-payment of scheduled principal and interest. Changes in economic conditions or other circumstances may reduce the capacity of the party obligated to make principal and interest payments on such instruments and may lead to defaults. Such non-payments and defaults may reduce the value of Trust shares and income distributions. The value of debt instruments also may decline because of concerns about the issuer’s ability to make principal and interest payments. In addition, the credit ratings of debt instruments may be lowered if the financial condition of the party obligated to make payments with respect to such instruments deteriorates. In the event of bankruptcy of the issuer of a debt instrument, the Trust could experience delays or limitations with respect to its ability to realize the benefits of any collateral securing the instrument. In order to enforce its rights in the event of a default, bankruptcy or similar situation, the Trust may be required

Eaton Vance Senior Income Trust

Prospectus dated [____], 2018

to retain legal or similar counsel, which may increase the Trust’s operating expenses and adversely affect net asset value. Due to their lower place in the borrower’s capital structure, Junior Loans involve a higher degree of overall risk than Senior Loans of the same borrower.

Rating agencies are private services that provide ratings of the credit quality of certain investments. In evaluating creditworthiness, the investment adviser considers ratings assigned by rating agencies and generally performs additional credit and investment analysis. Credit ratings issued by rating agencies are based on a number of factors including, but not limited to, the issuer’s financial condition and the rating agency’s credit analysis, if applicable, at the time of rating. The ratings assigned are not absolute standards of credit quality and do not evaluate market risks or necessarily reflect the issuer’s current financial condition or the volatility or liquidity of the security. An issuer’s current financial condition may be better or worse than the current rating indicates. A credit rating may have a modifier (such as plus, minus or a numerical modifier) to denote its relative status within the rating. The presence of a modifier does not change the security credit rating (for example, BBB- and Baa3 are within the investment grade rating) for purposes of the Trust’s investment limitations.

Interest Rate Risk. In general, the value of income securities will fluctuate based on changes in interest rates. The value of these securities is likely to increase when interest rates fall and decline when interest rates rise. Generally, securities with longer maturities are more sensitive to changes in interest rates than shorter maturity securities, causing them to be more volatile. Conversely, fixed income securities with shorter maturities will be less volatile but may provide lower returns than fixed income securities with longer maturities. The impact of interest rate changes on the value of floating rate instruments is typically reduced by periodic interest rate resets. In a rising interest rate environment, the maturities of income securities that have the ability to be prepaid or called by the issuer may be extended. In a declining interest rate environment, the proceeds from prepaid or maturing instruments may have to be reinvested at a lower interest rate. Because floating or variable rates on loans only reset periodically, changes in prevailing interest rates may cause some fluctuations in the Trust’s net asset value. Similarly, a sudden and significant increase in market interest rates may cause a decline in the Trust’s net asset value. A material decline in the Trust’s net asset value may impair the Trust’s ability to maintain required levels of asset coverage.

Non-Investment Grade Bonds Risk. The Trust’s investments in Non-Investment Grade Bonds, commonly referred to as “junk bonds,” are predominantly speculative because of the credit risk of their issuers. While offering a greater potential opportunity for capital appreciation and higher yields, Non-Investment Grade Bonds typically entail greater potential price volatility and may be less liquid than higher-rated securities. Issuers of Non-Investment Grade Bonds are more likely to default on their payments of interest and principal owed to the Trust, and such defaults will reduce the Trust’s net asset value and income distributions. The prices of these lower rated obligations are more sensitive to negative developments than higher rated securities. Adverse business conditions, such as a decline in the issuer’s revenues or an economic downturn, generally lead to a higher non-payment rate. In addition, a security may lose significant value before a default occurs as the market adjusts to expected higher non-payment rates.

Lower Rated Investments Risk. Investments rated below investment grade and comparable unrated investments (sometimes referred to as “junk”) have speculative characteristics because of the credit risk associated with their issuers. Changes in economic conditions or other circumstances typically have a greater effect on the ability of issuers of lower rated investments to make principal and interest payments than they do on issuers of higher rated investments. An economic downturn generally leads to a higher non-payment rate, and a lower rated investment may lose significant value before a default occurs. Lower rated investments typically are subject to greater price volatility and illiquidity than higher rated investments.

Prepayment Risk. During periods of declining interest rates or for other purposes, Borrowers may exercise their option to prepay principal earlier than scheduled. For fixed-income securities, such payments often occur during periods of declining interest rates, forcing the Trust to reinvest in lower yielding securities. This is known as call or prepayment risk. Non-Investment Grade Bonds frequently have call features that allow the issuer to redeem the security at dates prior to its stated maturity at a specified price (typically greater than par) only if certain prescribed conditions are met (“call protection”). An issuer may redeem a Non-Investment Grade Bond if, for example, the issuer can refinance the debt at a lower cost due to declining interest rates or an improvement in the credit standing of the issuer. Senior Loans typically have no such call protection. For premium bonds (bonds acquired at prices that exceed their par or principal value) purchased by the Trust, prepayment risk may be enhanced.

Issuer Risk. The value of corporate income-producing securities held by the Trust may decline for a number of reasons, which directly relate to the issuer, such as management performance, financial leverage and reduced demand for the issuer’s goods and services.

Eaton Vance Senior Income Trust

Prospectus dated [____], 2018

counterparty or due to tax or regulatory constraints. Derivatives may create leverage in the Trust, which represents a non-cash exposure to the underlying asset, index, rate or instrument. Leverage can increase both the risk and return potential of the Trust. Derivatives risk may be more significant when derivatives are used to enhance return or as a substitute for a cash investment position, rather than solely to hedge the risk of a position held by the Trust. Use of derivatives involves the exercise of specialized skill and judgment, and a transaction may be unsuccessful in whole or in part because of market behavior or unexpected events. Changes in the value of a derivative (including one used for hedging) may not correlate perfectly with the underlying asset, rate, index or instrument. Derivative instruments traded in over-the-counter markets may be difficult to value, may be illiquid, and may be subject to wide swings in valuation caused by changes in the value of the underlying instrument. If a derivative’s counterparty is unable to honor its commitments, the value of Trust shares may decline and the Trust could experience delays in the return of collateral or other assets held by the counterparty. The loss on derivative transactions may substantially exceed the initial investment, particularly when there is no stated limit on the Trust’s use of derivatives. A derivative investment also involves the risks relating to the asset, index, rate or instrument underlying the investment.

Leverage Risk. Certain fund transactions may give rise to leverage. Leverage can result from a non-cash exposure to an asset, index, rate or instrument. Leverage can increase both the risk and return potential of the Trust. The Trust is required to segregate liquid assets or otherwise cover the Trust’s obligation created by a transaction that may give rise to leverage. The use of leverage may cause the Trust to liquidate portfolio positions when it may not be advantageous to do so to satisfy its obligations or to meet segregation requirements. Leverage may cause the Trust’s share price to be more volatile than if it had not been leveraged, as certain types of leverage may exaggerate the effect of any increase or decrease in the value of the Trust’s portfolio securities. The loss on leveraged investments may substantially exceed the initial investment.

As discussed above, the Trust currently uses leverage created by issuing APS and borrowings. On June 27, 2001, the Trust issued 2,200 Series A APS and 2,200 Series B APS, with a liquidation preference per share of $25,000 plus accumulated but unpaid dividends. On September 23, 2016, the Trust repurchased 968 Series A APS and 968 Series B APS. On September 14, 2018, the Trust repurchased 480 Series A APS and 480 Series B APS. In addition, in connection with this repurchase, the Trust increased its borrowing limits under its Revolving Credit and Security Agreement, as amended (the “Agreement”) with conduit lenders and a bank to allow it to borrow up to $125 million ($100 million prior to September 13, 2018). The proceeds of which were used to invest in accordance with the Trust’s investment practices and to partially redeem the Trust’s APS. The Trust is required to maintain certain net asset levels during the term of the Agreement. As of September 30, 2018, the Trust had $113 million in outstanding borrowings, at an interest rate of 2.21%, in addition to outstanding APS.

The Adviser anticipates that the use of leverage (from the issuance of APS and borrowings) may result in higher income to Common Shareholders over time. Leverage creates risks for Common Shareholders, including the likelihood of greater volatility of NAV and market price of the Common Shares and the risk that fluctuations in dividend rates on APS and costs of borrowings may affect the return to Common Shareholders. To the extent the income derived from investments purchased with funds received from leverage exceeds the cost of leverage, the Trust’s distributions will be greater than if leverage had not been used. Conversely, if the income from the investments purchased with such funds is not sufficient to cover the cost of leverage, the amount available for distribution to Common Shareholders will be less than if leverage had not been used. In the latter case, Eaton Vance, in its best judgment, may nevertheless determine to maintain the Trust’s leveraged position if it deems such action to be appropriate. While the Trust has preferred shares outstanding, an increase in short-term rates would also result in an increased cost of leverage, which would adversely affect the Trust’s income available for distribution. There can be no assurance that a leveraging strategy will be successful.

In addition, under current federal income tax law, the Trust is required to allocate a portion of any net realized capital gains or other taxable income to APS holders. The terms of the Trust’s APS require the Trust to pay to any APS holders additional dividends intended to compensate such holders for taxes payable on any capital gains or other taxable income allocated to such holders. Any such additional dividends will reduce the amount available for distribution to Common Shareholders. As discussed under “Management of the Trust,” the fee paid to Eaton Vance is calculated on the basis of the Trust’s gross assets, including proceeds from the issuance of APS and borrowings, so the fees will be higher when leverage is utilized. In this regard, holders of APS do not bear the investment advisory fee. Rather, Common Shareholders bear the portion of the investment advisory fee attributable to the assets purchased with the proceeds, which means that Common Shareholders effectively bear the entire advisory fee.

The APS have been rated Aa3 by Moody's. The Trust currently intends to seek to maintain this rating or an equivalent credit rating on the APS or any preferred shares it issues. The Rating Agencies which rate the preferred shares and any bank lender in connection with a credit facility or commercial paper program may also impose specific restrictions as a condition to borrowing. Such restrictions may include asset coverage or portfolio composition requirements that are more stringent than those imposed on the Trust by the 1940 Act. These covenants or guidelines do not currently and are not expected to impede Eaton Vance in managing the Trust’s portfolio in accordance with its investment objective and policies and it is not anticipated that they will so impede Eaton Vance in the future. See “Description of Capital Structure - Preferred Shares.”

Eaton Vance Senior Income Trust

Prospectus dated [____], 2018

Foreign Investment Risk. Investments in foreign issuers could be affected by factors not present in the United States, including expropriation, armed conflict, confiscatory taxation, lack of uniform accounting and auditing standards, less publicly available financial and other information, and potential difficulties in enforcing contractual obligations. Because foreign issuers may not be subject to uniform accounting, auditing and financial reporting standard practices and requirements and regulatory measures comparable to those in the United States, there may be less publicly available information about such foreign issuers. Settlements of securities transactions in foreign countries are subject to risk of loss, may be delayed and are generally less frequent than in the United States, which could affect the liquidity of the Trust’s assets. Evidence of ownership of certain foreign investments may be held outside the United States, and the Trust may be subject to the risks associated with the holding of such property overseas.

Foreign issuers may become subject to sanctions imposed by the United States or another country, which could result in the immediate freeze of the foreign issuers’ assets or securities. The imposition of such sanctions could impair the market value of the securities of such foreign issuers and limit the Trust’s ability to buy, sell, receive or deliver the securities. Trading in certain foreign markets is also subject to liquidity risks.

Currency Risk. Exchange rates for currencies fluctuate daily. The value of foreign investments may be affected favorably or unfavorably by changes in currency exchange rates in relation to the U.S. dollar. Currency markets generally are not as regulated as securities markets and currency transactions are subject to settlement, custodial and other operational risks.

U.S. Government Securities Risk. Although certain U.S. Government-sponsored agencies (such as the Federal Home Loan Mortgage Corporation and the Federal National Mortgage Association) may be chartered or sponsored by acts of Congress, their securities are neither issued nor guaranteed by the U.S. Treasury. U.S. Treasury securities generally have a lower return than other obligations because of their higher credit quality and market liquidity.

Liquidity Risk. The Trust may invest without limitation in Senior Loans and other securities for which there is no readily available trading market or which are otherwise illiquid. The Trust may not be able to dispose readily of such securities at prices that approximate those at which the Trust could sell such securities if they were more widely traded and, as a result of such illiquidity, the Trust may have to sell other investments or engage in borrowing transactions if necessary to raise cash to meet its obligations. In addition, the limited liquidity could affect the market price of the securities, thereby adversely affecting the Trust's net asset value and ability to make dividend distributions.

Some Senior Loans are not readily marketable and may be subject to contractual restrictions that must be satisfied before a loan can be bought or sold. Senior Loans generally are not listed on any national securities exchange or automated quotation system and no active trading market may exist for some of the Senior Loans in which the Trust will invest. Where a secondary market exists, such market for some Senior Loans may be subject to irregular activity, wide bid/ask spreads and extended trade settlement periods. Senior Loans that are illiquid may impair the Trust’s ability to realize the full value of its assets in the event of a voluntary or involuntary liquidation of such assets and thus may cause a decline in the Trust’s net asset value. The Trust has no limitation on the amount of its assets which may be invested in securities which are not readily marketable or are subject to restrictions on resale.

Money Market Instrument Risk. Money market instruments may be adversely affected by market and economic events, such as a sharp rise in prevailing short-term interest rates; adverse developments in the banking industry, which issues or guarantees many money market instruments; adverse economic, political or other developments affecting issuers of money market instruments; changes in the credit quality of issuers; and default by a counterparty.

Reinvestment Risk. Income from the Trust’s portfolio will decline if and when the Trust invests the proceeds from matured, traded or called debt obligations into lower yielding instruments.

Inflation Risk. Inflation risk is the risk that the value of assets or income from investment will be worth less in the future as inflation decreases the value of money. As inflation increases, the real value of the Common Shares and distributions thereon can decline. In addition, during any periods of rising inflation, dividend rates of preferred shares would likely increase, which would tend to further reduce returns to Common Shareholders. This risk is mitigated to some degree by the Trust's investments in Senior Loans.

Eaton Vance Senior Income Trust

Prospectus dated [____], 2018

Eaton Vance and the individual portfolio managers to develop and effectively implement strategies that achieve the Trust’s investment objective. There is no assurance that Eaton Vance and the individual portfolio managers will be successful in developing and implementing the Trust’s investment strategy. Subjective decisions made by Eaton Vance and the individual portfolio managers may cause the Trust to incur losses or to miss profit opportunities.

Regulatory Risk. To the extent that legislation or state or federal regulators that regulate certain financial institutions impose additional requirements or restrictions with respect to the ability of such institutions to make loans, particularly in connection with highly leveraged transactions, the availability of Senior Loans for investment may be adversely affected. Further, such legislation or regulation could depress the market value of Senior Loans.

Market Disruption. Instability in the Middle East, the wars in Afghanistan, Iraq and Libya, geopolitical tensions elsewhere and terrorist attacks in the United States and around the world have resulted in market volatility and may have long-term effects on the United States and worldwide financial markets and may cause further economic uncertainties in the United States and worldwide. The Trust cannot predict the effects of significant future events on the global economy and securities markets. A similar disruption of the financial markets could impact interest rates, auctions, secondary trading, ratings, credit risk, inflation and other factors relating to the Common Shares. In particular, Non-Investment Grade Bonds and Senior Loans tend to be more volatile than higher rated fixed-income securities so that these events and any actions resulting from them may have a greater impact on the prices and volatility on Non-Investment Grade Bonds and Senior Loans than on higher rated fixed-income securities.

Anti-takeover Provisions. The Trust's Agreement and Declaration of Trust includes provisions that could have the effect of limiting the ability of other persons or entities to acquire control of the Trust or to change the composition of its Board. These provisions may have the effect of discouraging attempts to acquire control of the Trust, which attempts could have the effect of increasing the expenses of the Trust and interfering with the normal operation of the Trust. See “Description of Capital Structure - Certain Provisions of the Declaration of Trust - Anti-Takeover Provisions in the Declaration of Trust.”

Eaton Vance Senior Income Trust

Prospectus dated [____], 2018

Summary of Trust Expenses

The purpose of the table below is to help you understand all fees and expenses that you, as a holder of Common Shares (“Common Shareholder”), would bear directly or indirectly. The table reflects the issuance of preferred shares in an amount equal to 14.7% of the Trust’s total assets and borrowings in an amount equal to 20.7% of the Trust’s total assets (including the proceeds of all such leverage) and shows Trust expenses as a percentage of net assets attributable to Common Shares⁽¹⁾ for the year ended June 30, 2018.

Common Shareholder transaction expenses
Sales load paid by you (as a percentage of offering price)	--%⁽¹⁾
Offering expenses (as a percentage of offering price)	None⁽²⁾
Dividend reinvestment plan fees	None⁽³⁾

Annual expenses	Percentage of net assets attributable to Common Shares⁽⁴⁾⁽⁷⁾
Investment advisory fee	1.19%⁽⁵⁾
Interest payments on borrowed funds	0.83%⁽⁶⁾
Other expenses	0.63%
Acquired fund fees and expenses	0.05%
Total annual Trust operating expenses	2.70%
Dividends on preferred shares	0.40%⁽⁶⁾
Total annual Trust operating expenses and dividends on preferred shares	3.10%

EXAMPLE

The following example illustrates the expenses that Common Shareholders would pay on a $1,000 investment in Common Shares, assuming (i) total annual expenses of 3.10% of net assets attributable to Common Shares in years 1 through 10; (ii) a 5% annual return; and (iii) all distributions are reinvested at NAV:

1 Year	3 Years	5 Years	10 Years
$31	$96	$163	$341

The above table and example and the assumption in the example of a 5% annual return are required by regulations of the SEC that are applicable to all investment companies; the assumed 5% annual return is not a prediction of, and does not represent, the projected or actual performance of the Trust’s Common Shares. For more complete descriptions of certain of the Trust’s costs and expenses, see “Management of the Trust.” In addition, while the example assumes reinvestment of all dividends and distributions at NAV, participants in the Trust’s dividend reinvestment plan may receive Common Shares purchased or issued at a price or value different from NAV. See “Distributions” and “Dividend Reinvestment Plan.” The example does not include sales load or estimated offering costs, which would cause the expenses shown in the example to increase.

The example should not be considered a representation of past or future expenses, and the Trust’s actual expenses may be greater or less than those shown. Moreover, the Trust’s actual rate of return may be greater or less than the hypothetical 5% return shown in the example.

Eaton Vance Senior Income Trust

Prospectus dated [____], 2018

⁽¹⁾

If Common Shares are sold to or through underwriters, the Prospectus Supplement will set forth any applicable sales load.

⁽²⁾

The Adviser will pay the expenses of the Offering (other than the applicable commissions); therefore, Offering expenses are not included in the Summary of Trust Expenses. Offering expenses generally include, but are not limited to, the preparation, review and filing with the SEC of the Trust’s registration statement (including this Prospectus and the Statement of Additional Information), the preparation, review and filing of any associated marketing or similar materials, costs associated with the printing, mailing or other distribution of the prospectus, Statement of Additional Information and/or marketing materials, associated filing fees, NYSE listing fees, and legal and auditing fees associated with the Offering.

⁽³⁾

You will be charged a $5.00 service charge and pay brokerage charges if you direct the plan agent to sell your Common Shares held in a dividend reinvestment account.

⁽⁴⁾

Stated as a percentage of average net assets attributable to Common Shares for the year ended June 30, 2018.

⁽⁵⁾

The advisory fee paid by the Trust to the Adviser is based on the average weekly gross assets of the Trust, including all assets attributable to any form of investment leverage that the Trust may utilize. Accordingly, if the Trust were to increase investment leverage in the future, the advisory fee will increase as a percentage of net assets. Pursuant to the investment advisory agreement and fee reduction agreement between the Trust and the Adviser, the fee is computed at an annual rate of 0.76% (0.77% prior to May 1, 2018) of the Trust’s average weekly gross assets and is payable monthly. Pursuant to a fee reduction agreement between the Trust and EVM that commenced on May 1, 2010, the annual adviser fee rate is reduced by 0.01% every May 1 thereafter for the next twenty-nine years.

⁽⁶⁾

As of June 30, 2018, the outstanding borrowings and APS represented approximately 36.2% leverage. As of September 30, 2018, the outstanding borrowings and APS represented approximately 32.4% leverage. Amounts have been estimated for the current fiscal year.

⁽⁷⁾

Ratios have been restated to reflect the repurchase of 480 Series A APS and 480 Series B APS on September 14, 2018 and the increase in Trust’s borrowings subsequent to June 30, 2018.

Eaton Vance Senior Income Trust

Prospectus dated [____], 2018

Financial Highlights and Investment Performance

FINANCIAL HIGHLIGHTS

This table details the financial performance of the Common Shares, including total return information showing how much an investment in the Trust has increased or decreased each period. This information has been audited by [______________], an independent registered public accounting firm. The report of [___________] and the Trust’s financial statements are incorporated by reference and included in the Trust’s annual report, which is available upon request.

Selected data for a common share outstanding during the periods stated.

	Year Ended June 30,
	2018	2017	2016	2015	2014
Net asset value – Beginning of year (Common shares)	$7.150	$6.650	$7.020	$7.340	$7.350
Income (Loss) From Operations
Net investment income⁽¹⁾	$0.385	$0.404	$0.422	$0.401	$0.406
Net realized and unrealized gain (loss)	0.038	0.436	(0.371)	(0.316)	0.029
Distributions to preferred shareholders – From net investment income⁽¹⁾	(0.028)	(0.014)	(0.009)	(0.003)	(0.002)
Discount on redemption and repurchase of auction preferred shares⁽¹⁾	—	0.064	—	—	—
Total income from operations	$0.395	$0.890	$0.042	$0.082	$0.433
Less Distributions to Common Shareholders
From net investment income	$(0.365)	$(0.390)	$(0.412)	$(0.402)	$(0.443)
Total distributions to common shareholders	$(0.365)	$(0.390)	$(0.412)	$(0.402)	$(0.443)
Net asset value – End of year (Common shares)	$7.180	$7.150	$6.650	$7.020	$7.340
Market value – End of year (Common shares)	$6.380	$6.650	$6.010	$6.210	$6.810
Total Investment Return on Net Asset Value⁽²⁾	6.12%	14.02%⁽³⁾	1.57%	1.71%	6.34%
Total Investment Return on Market Value⁽²⁾	1.39%	17.34%	3.77%	(3.02)%	(3.57)%
Ratios/Supplemental Data
Net assets applicable to common shares, end of year (000’s omitted)	$272,016	$270,810	$251,789	$266,009	$278,045
Ratios (as a percentage of average daily net assets applicable to common shares)^(4)†
Expenses excluding interest and fees⁽⁵⁾	1.82%	1.87%	1.96%	1.99%	1.98%
Interest and fee expense⁽⁶⁾	0.83%	0.52%	0.28%	0.28%	0.27%
Total expenses⁽⁵⁾	2.65%	2.39%	2.24%	2.27%	2.25%
Net investment income	5.36%	5.75%	6.38%	5.61%	5.51%
Portfolio Turnover	34%	42%	31%	33%	33%
Senior Securities:
Total notes payable outstanding (in 000’s)	$93,000	$92,000	$25,000	$60,000	$65,000
Asset coverage per $1,000 of notes payable⁽⁷⁾	$4,587	$4,613	$15,472	$7,267	$6,970
Total preferred shares outstanding	2,464	2,464	4,400	4,400	4,400
Asset coverage per preferred share⁽⁸⁾	$68,989	$69,078	$71,629	$64,119	$64,721
Involuntary liquidation preference per preferred share⁽⁹⁾	$25,000	$25,000	$25,000	$25,000	$25,000
Approximate market value per preferred share⁽⁹⁾	$25,000	$25,000	$25,000	$25,000	$25,000

(See footnotes on last page.)

Eaton Vance Senior Income Trust

Prospectus dated [____], 2018

Financial Highlights (continued)

	Year Ended June 30,
	2013	2012	2011	2010	2009
Net asset value – Beginning of year (Common shares)	$7.160	$7.240	$6.710	$5.480	$7.480
Income (Loss) From Operations
Net investment income⁽¹⁾	$0.468	$0.435	$0.420	$0.395	$0.492
Net realized and unrealized gain (loss)	0.194	(0.071)	0.557	1.198	(2.012)
Distributions to preferred shareholders – From net investment income⁽¹⁾	(0.003)	(0.003)	(0.006)	(0.006)	(0.033)
Total income (loss) from operations	$0.659	$0.361	$0.971	$1.587	$(1.553)
Less Distributions to Common Shareholders
From net investment income	$(0.476)	$(0.441)	$(0.441)	$(0.357)	$(0.439)
Tax return of capital	—	—	—	—	(0.008)
Total distributions to common shareholders	$(0.476)	$(0.441)	$(0.441)	$(0.357)	$(0.447)
Premium from common shares sold through shelf offering⁽¹⁾	$0.007	$—	$—	$—	$—
Net asset value – End of year (Common shares)	$7.350	$7.160	$7.240	$6.710	$5.480
Market value – End of year (Common shares)	$7.520	$7.020	$7.200	$6.630	$4.690
Total Investment Return on Net Asset Value⁽²⁾	9.49%	5.58%	14.80%	29.77%	(18.99)%
Total Investment Return on Market Value⁽²⁾	14.26%	4.09%	15.55%	49.83%	(21.66)%
Ratios/Supplemental Data
Net assets applicable to common shares, end of year (000’s omitted)	$278,364	$263,168	$265,927	$245,741	$200,183
Ratios (as a percentage of average daily net assets applicable to common shares)^(4)†
Expenses excluding interest and fees⁽⁵⁾	1.98%	2.01%	1.95%	2.05%	2.44%
Interest and fee expense⁽⁶⁾	0.23%	0.23%	0.23%	0.25%	0.99%
Total expenses⁽⁵⁾	2.21%	2.24%	2.18%	2.30%	3.43%
Net investment income	6.35%	6.17%	5.90%	6.08%	9.64%
Portfolio Turnover	52%	38%	53%	43%	18%
Senior Securities:
Total notes payable outstanding (in 000’s)	$65,000	$46,000	$36,000	$31,000	$3,000
Asset coverage per $1,000 of notes payable⁽⁷⁾	$6,975	$9,112	$11,442	$12,476	$104,397
Total preferred shares outstanding	4,400	4,400	4,400	4,400	4,400
Asset coverage per preferred share⁽⁸⁾	$64,766	$67,174	$70,536	$68,571	$69,290
Involuntary liquidation preference per preferred share⁽⁹⁾	$25,000	$25,000	$25,000	$25,000	$25,000
Approximate market value per preferred share⁽⁹⁾	$25,000	$25,000	$25,000	$25,000	$25,000

(See footnotes on next page.)

Eaton Vance Senior Income Trust

Prospectus dated [____], 2018

⁽¹⁾

Computed using average common shares outstanding.

⁽²⁾

Returns are historical and are calculated by determining the percentage change in net asset value or market value with all distributions reinvested. Distributions are assumed to be reinvested at prices obtained under the Trust’s dividend reinvestment plan.

⁽³⁾

The total return based on net asset value reflects the impact of the tender and repurchase by the Trust of a portion of its Auction Preferred Shares at 95% of the per share liquidation preference. Absent this transaction, the total return based on net asset value would have been 13.00%.

⁽⁴⁾

Ratios do not reflect the effect of dividend payments to preferred shareholders.

⁽⁵⁾

Excludes the effect of custody fee credits, if any, of less than 0.005%. Effective September 1, 2015, custody fee credits, which were earned on cash deposit balances, were discontinued by the custodian.

⁽⁶⁾

Interest and fee expense relates to the notes payable to partially redeem the Trust’s Auction Preferred Shares and/or to fund investments.

⁽⁷⁾

Calculated by subtracting the Trust’s total liabilities (not including the notes payable and preferred shares) from the Trust’s total assets, and dividing the result by the notes payable balance in thousands.

⁽⁸⁾

Calculated by subtracting the Trust’s total liabilities (not including the notes payable and preferred shares) from the Trust’s total assets, dividing the result by the sum of the value of the notes payable and liquidation value of the preferred shares, and multiplying the result by the liquidation value of one preferred share. Such amount equates to 276%, 276%, 287%, 256%, 259%, 259%, 269%, 282%, 274% and 277% at June 30, 2018, 2017, 2016, 2015, 2014, 2013, 2012, 2011, 2010 and 2009, respectively.

⁽⁹⁾

Plus accumulated and unpaid dividends.

^†

Ratios based on net assets applicable to common shares plus preferred shares and borrowings are presented below. Ratios do not reflect the effect of dividend payments to preferred shareholders and exclude the effect of custody fee credits, if any.

	Year Ended June 30,
	2018	2017	2016	2015	2014	2013	2012	2011	2010	2009
Expenses excluding interest and fees	1.17%	1.21%	1.21%	1.21%	1.22%	1.25%	1.27%	1.26%	1.31%	1.54%
Interest and fee expense	0.54%	0.34%	0.17%	0.17%	0.17%	0.15%	0.15%	0.15%	0.16%	0.62%
Total expenses	1.71%	1.55%	1.38%	1.38%	1.39%	1.40%	1.42%	1.41%	1.47%	2.16%
Net investment income	3.46%	3.72%	3.93%	3.42%	3.39%	4.03%	3.93%	3.82%	3.90%	6.06%

TRADING AND NAV INFORMATION

The Trust’s common shares have traded both at a premium and a discount to NAV. The Trust cannot predict whether its shares will trade in the future at a premium or discount to NAV. The provisions of the 1940 Act generally require that the public offering price of common shares (less any underwriting commissions and discounts) must equal or exceed the NAV per share of a company’s common stock (calculated within 48 hours of pricing). The issuance of common shares may have an adverse effect on prices in the secondary market for the Trust’s common shares by increasing the number of common shares available, which may put downward pressure on the market price for the Trust’s common shares. Shares of common stock of closed-end investment companies frequently trade at a discount from NAV. See “Additional Risk Considerations - Discount from or Premium to NAV”.

In addition, the Trust’s Board of Trustees has authorized the Trust to repurchase up to 10% of its outstanding common shares (as of the date of such authorization) in open-market transactions at a discount to NAV. The repurchase program does not obligate the Trust to purchase a specific amount of shares. The results of the repurchase program are disclosed in the Trust’s annual and semi-annual reports to shareholders. See “Description of Capital Structure - Repurchase of Common Shares and Other Discount Measures.”

Eaton Vance Senior Income Trust

Prospectus dated [____], 2018

The following table sets forth for each of the periods indicated the high and low closing market prices for Common Shares on the NYSE, and the corresponding NAV per share and the premium or discount to NAV per share at which the Trust’s Common Shares were trading as of such date.

	Market Price		NAV per Share on Date of Market Price High and Low		NAV Premium/(Discount) on Date of Market Price High and Low
Fiscal Quarter Ended	High	Low	High	Low	High	Low
9/30/2018	6.53	6.32	7.33	7.18	(10.91)%	(11.98)%
6/30/2018	6.84	6.38	7.24	7.18	(5.52)%	(11.14)%
3/31/2018	6.81	6.42	7.24	7.14	(5.94)%	(10.08)%
12/31/2017	6.62	6.35	7.18	7.13	(7.80)%	(10.94)%
9/30/2017	6.74	6.52	7.18	7.12	(6.13)%	(8.43)%
6/30/2017	6.90	6.59	7.17	7.14	(3.77)%	(7.70)%
3/31/2017	6.98	6.67	7.18	7.09	(2.79)%	(5.92)%
12/31/2016	6.68	6.27	7.07	6.98	(5.52)%	(10.17)%
9/30/2016	6.44	6.03	6.95	6.66	(7.34)%	(9.46)%

The last reported sale price, NAV per share and percentage premium/(discount) to NAV per share of the Common Shares as of [_______], 2018 were $[_____], $[_____] and [_____]%, respectively. As of [_______], 2018, the Trust had [________] Common Shares outstanding and net assets of the Trust were $[_______].

The Trust

The Trust is a diversified, closed-end management investment company registered under the 1940 Act. The Trust was organized as a Massachusetts business trust on September 23, 1998, pursuant to a Declaration of Trust, as amended August 11, 2008, governed by the laws of The Commonwealth of Massachusetts. The Trust’s principal office is located at Two International Place, Boston, MA 02110, and its telephone number is 1-800-262-1122.

Use of Proceeds

Subject to the remainder of this section, and unless otherwise specified in a Prospectus Supplement, the Trust currently intends to invest substantially all of the net proceeds of any sales of Common Shares pursuant to this Prospectus in accordance with its Trust’s investment objective and policies within three months of receipt of such proceeds. Such investments may be delayed up to three months if suitable investments are unavailable at the time or for other reasons, such as market volatility and lack of liquidity in the markets of suitable investments. Pending such investment, the Trust anticipates that it will invest the proceeds in short-term money market instruments, securities with remaining maturities of less than one year, cash or cash equivalents. A delay in the anticipated use of proceeds could lower returns and reduce the Trust’s distribution to Common Shareholders or result in a distribution consisting principally of a return of capital.

Eaton Vance Senior Income Trust

Prospectus dated [____], 2018

Portfolio Composition

As of June 30, 2018, the following table indicates the approximate percentage of the Trust's portfolio invested in long-term and short-term obligations and also includes other information with respect to the composition of the Trust’s investment portfolio:

S&P⁽¹⁾	Number of issues	Mkt Value	Percent
BBB	41	$23,966,140	5.67%
BB	189	$142,089,235	33.59%
B	295	$210,995,662	49.89%
CCC	34	$16,547,650	3.91%
D	3	$1,182,618	0.28%
NR	35	$21,393,112	5.09%

Cash and cash equivalents		$6,799,543	1.61%

Total	597	$422,973,960	100%

⁽¹⁾

Ratings: Using S&P’s ratings on the Trust’s investments. S&P rating categories may be modified further by a plus (+) or minus (—) in AA, A, BBB, BB, B, and CCC ratings.

Investment Objective, Policies and Risks

INVESTMENT OBJECTIVE

The Trust's investment objective is to provide shareholders with a high level of current income, consistent with the preservation of capital. The Trust pursues its objective by investing its assets primarily in senior, secured floating-rate loans (“Senior Loans”). Senior Loans are loans in which the interest rate paid fluctuates based on a reference rate. Investment in such floating-rate instruments is expected to minimize changes in the underlying principal value of the Senior Loans, and therefore the Trust's net asset value, resulting from changes in market interest rates. Senior Loans are made to corporations, partnerships and other business entities (“Borrowers”) that operate in a variety of industries and geographical regions. Senior Loans pay interest at rates that are reset periodically by reference to a base lending rate, primarily LIBOR, plus a premium.

PRIMARY INVESTMENT POLICIES

General Composition of the Trust. Under normal market conditions, the Trust will invest at least 80% of its total assets in Senior Loans of domestic and foreign borrowers that are denominated in U.S. dollars, euros, British pounds, Swiss francs, Canadian dollars and Australian dollars (each, an “Authorized Foreign Currency”) making payments in such Authorized Foreign Currency. For the purposes of the 80% test, total assets is defined as net assets plus any borrowings for investment purposes, including any outstanding preferred shares. The Trust may also invest up to 15% of its net assets in foreign Senior Loans denominated in an Authorized Foreign Currency. For all foreign Senior Loan investments denominated in an Authorized Foreign Currency, the Adviser currently intends to hedge against foreign currency fluctuations through the use of currency exchange contracts and other appropriate permitted hedging strategies. The Trust may invest up to 20% of its total assets in (i) loan interests which have (a) a second lien on collateral, (b) no security interest in the collateral, or (c) lower than a senior claim on collateral; (ii) other income-producing securities, such as investment and non-investment grade corporate debt securities and U.S. government and U.S. dollar-denominated foreign government or supranational debt securities; and (iii) warrants and equity securities issued by a Borrower or its affiliates as part of a package of investments in the Borrower or its affiliates. If the Adviser determines that market conditions temporarily warrant a defensive investment policy, the Trust may invest up to 100% of its assets in cash and/or high quality, short-term debt securities, which would not be consistent with the Trust’s investment objective and other policies. While temporarily invested, the Trust may not achieve its investment objective. Corporate bonds of below investment grade quality (“Non-Investment Grade Bonds”), commonly referred to as “junk bonds,” which are bonds that are rated below investment grade by each of the Rating Agencies who cover the security, or, if unrated, are determined to be of comparable quality by the Adviser. S&P and Fitch consider securities rated below BBB- to be below investment grade and Moody’s considers securities rated below Baa3 to be below investment grade. The Trust’s credit quality policies apply only at the time a security is purchased, and the Trust is not required to dispose of a security in the event of

Eaton Vance Senior Income Trust

Prospectus dated [____], 2018

a downgrade of an assessment of credit quality, the withdrawal of a rating, or in the event of a default. In determining whether to retain or sell such a security, Eaton Vance may consider such factors as Eaton Vance’s assessment of the credit quality of the issuers of such security, the price at which such security could be sold and the rating, if any, assigned to such security by other Rating Agencies. Securities rated in the lowest investment grade rating (BBB- or Baa3) may have certain speculative characteristics. Below investment grade quality securities are considered to be predominantly speculative because of the credit risk of the issuers. See “Investment Objective, Policies and Risks - Risk Considerations - Non-Investment Grade Bonds Risk.”

The Trust’s policy of investing, under normal market conditions, at least 80% of its total assets in Senior Loans is not considered to be fundamental by the Trust and can be changed without a vote of the Trust’s shareholders. However, this policy may only be changed by the Trust’s Board following the provision of 60 days prior written notice to the Trust’s shareholders.

The Trust is not subject to any restrictions with respect to the maturity of Senior Loans held in its portfolio.

A lender may have certain obligations pursuant to a loan agreement relating to Senior Loans, which may include the obligation to make additional loans in certain circumstances. The Trust generally will reserve against such contingent obligations by segregating a sufficient amount of cash, liquid securities and liquid Senior Loans, subject to the Trust's borrowing limitations. The Trust will not purchase interests in Senior Loans that would require the Trust to make any such additional loans if such additional loan commitments in the aggregate would exceed 20% of the Trust's total assets or would cause the Trust to fail to meet its tax diversification requirements.

The Adviser’s staff monitors the credit quality and the price of Senior Loans and other securities held by the Trust, as well as other securities that are available to the Trust. The Trust may invest in Senior Loans and other securities of any credit quality. Although the Adviser considers ratings when making investment decisions, it generally performs its own credit and investment analysis and does not rely primarily on the ratings assigned by the Rating Agencies. In evaluating the quality of a particular security, whether rated or unrated, the Adviser will normally take into consideration, among other things, the issuer’s financial resources and operating history, its sensitivity to economic conditions and trends, the ability of its management, its debt maturity schedules and borrowing requirements, and relative values based on anticipated cash flow, interest and asset coverage, and earnings prospects. The Adviser will attempt to reduce the risks of investing in lower rated or unrated debt instruments through active portfolio management, credit analysis and attention to current developments and trends in the economy and the financial markets.

The Trust is not required to dispose of a security in the event that a Rating Agency downgrades its assessment of the credit characteristics of a particular issue or withdraws its assessment, including in the event of a default. In determining whether to retain or sell such a security, Eaton Vance may consider such factors as Eaton Vance's assessment of the credit quality of the issuers of such security, the price at which such security could be sold and the rating, if any, assigned to such security by other Rating Agencies.

The Trust may purchase shares of other investment companies with a similar investment objective and policies as permitted under the 1940 Act. Such investments are limited to 10% of total assets overall, with no more than 5% invested in any one issuer. The value of shares of other closed-end investment companies is affected by risks similar to those of the Trust, such as demand for those securities regardless of the demand for the underlying portfolio assets. Investment companies bear fees and expenses that the Trust will bear indirectly, so investors in the Trust will be subject to duplication of fees. The Trust also may invest up to 5% of its total assets in structured notes with rates of return determined by reference to the total rate of return on one or more Senior Loans referenced in such notes. The rate of return on the structured note may be determined by applying a multiplier to the rate of total return on the referenced Senior Loan or Loans. Application of a multiplier is comparable to the use of financial leverage, a speculative technique. Leverage magnifies the potential for gain and the risk of loss; as a result, a relatively small decline in the value of a referenced Senior Loan could result in a relatively large loss in the value of a structured note. Common Shares of other investment companies and structured notes as discussed above that invest in Senior Loans or baskets of Senior Loans will be treated as Senior Loans for purposes of the Trust’s policy of normally investing at least 80% of its assets in Senior Loans, and may be subject to the Trust’s leverage limitations.

Eaton Vance Senior Income Trust

Prospectus dated [____], 2018

Senior Loans. Senior Loans hold a senior position in the capital structure of a Borrower, are typically secured with specific collateral and have a claim on the assets and/or stock of the Borrower that is senior to that held by subordinated debt holders and stockholders of the Borrower. The capital structure of a Borrower may include Senior Loans, senior and junior subordinated debt, preferred stock and common stock issued by the Borrower, typically in descending order of seniority with respect to claims on the Borrower’s asset. Senior Loans are typically secured by specific collateral. As also discussed above, the proceeds of Senior Loans primarily are used to finance leveraged buyouts, recapitalizations, mergers, acquisitions, stock repurchases, refinancing and internal growth and for other corporate purposes.

Senior Loans in which the Trust will invest generally pay interest at rates, which are reset periodically by reference to a base lending rate, plus a premium. Senior Loans typically have rates of interest which are reset either daily, monthly, quarterly or semi-annually by reference to a base lending rate, plus a premium or credit spread. These base lending rates are primarily LIBOR, and secondarily the prime rate offered by one or more major United States banks (the “Prime Rate”) and the certificate of deposit (“CD”) rate or other base lending rates used by commercial lenders. Floating-rate loans typically have rates of interest which are re-determined daily, monthly, quarterly or semi-annually by reference to a base lending rate, plus a premium. As floating-rate loans, the frequency of how often a loan resets its interest rate will impact how closely such loans track current market interest rate. The Senior Loans held by the Trust will have a dollar-weighted average period until the next interest rate adjustment of approximately 90 days or less. As a result, as short-term interest rates increase, interest payable to the Trust from its investments in Senior Loans should increase, and as short-term interest rates decrease, interest payable to the Trust from its investments in Senior Loans should decrease. The Trust may utilize derivative instruments to shorten the effective interest rate redetermination period of Senior Loans in its portfolio. Senior Loans typically have a stated term of between one and ten years. In the experience of the Adviser over the last decade, however, the average life of Senior Loans has been two to four years because of prepayments.

Loans may be primary, direct investments or investments in loan assignments or participation interests. A loan assignment represents a portion of the entirety of a loan and a portion of the entirety of a position previously attributable to a different lender. The purchaser of an assignment typically succeeds to all the rights and obligations under the loan agreement and has the same rights and obligations as the assigning investor. However, assignments through private negotiations may cause the purchaser of an assignment to have different and more limited rights than those held by the assigning investor. Loan participation interests are interests issued by a lender or other entity and represent a fractional interest in a loan. The Trust typically will have a contractual relationship only with the financial institution that issued the participation interest. As a result, the Trust may have the right to receive payments of principal, interest and any fees to which it is entitled only from the financial institution and only upon receipt by such entity of such payments from the borrower. In connection with purchasing a participation interest, the Trust generally will have no right to enforce compliance by the borrower with the terms of the loan agreement, nor any rights with respect to any Trusts acquired by other investors through set-off against the borrower and the Trust may not directly benefit from the collateral supporting the loan in which it has purchased the participation interest. As a result, the Trust may assume the credit risk of both the borrower and the financial institution issuing the participation interest. In the event of the insolvency of the entity issuing a participation interest, the Trust may be treated as a general creditor of such entity. No active trading market may exist for certain loans, which may impair the ability of the Trust to realize full value in the event of the need to sell a loan and which may make it difficult to value the loan. To the extent that a secondary market does exist for certain loans, the market may be subject to irregular trading activity, wide bid/ask spreads and extended trade settlement periods. Most loans are rated below investment grade or, if unrated, are of similar credit quality.

Loan investments may be made at par or at a discount or premium to par. The interest payable on a loan may be fixed or floating rate, and paid in cash or in-kind. In connection with transactions in loans, the Trust may be subject to facility or other fees. Loans may be secured by specific collateral or other assets of the borrower, guaranteed by a third party, unsecured or subordinated. During the term of a loan, the value of any collateral securing the loan may decline in value, causing the loan to be under collateralized. Collateral may consist of assets that may not be readily liquidated, and there is no assurance that the liquidation of such assets would satisfy fully a borrower’s obligations under the loan. In addition, if a loan is foreclosed, the Trust could become part owner of the collateral and would bear the costs and liabilities associated with owning and disposing of such collateral.

A lender’s repayment and other rights primarily are determined by governing loan, assignment or participation documents, which (among other things) typically establish the priority of payment on the loan relative to other indebtedness and obligations of the borrower. In the event of bankruptcy, applicable law may impact a lender’s ability to enforce its rights under such documents.

Loans may be originated by a lending agent, such as a financial institution or other entity, on behalf of a group or “syndicate” of loan investors (the “Loan Investors”). In such a case, the agent administers the terms of the loan agreement and is responsible for the collection of principal, and interest payments from the borrower and the apportionment of these payments to the Loan Investors. Failure by the agent to fulfill its obligations may delay or adversely affect receipt of payment by the Trust. Furthermore, unless under the terms of a loan agreement or participation (as applicable) the Trust has direct recourse against the borrower, the Trust must rely on the agent and the other Loan Investors to pursue appropriate remedies against the borrower.

Eaton Vance Senior Income Trust

Prospectus dated [____], 2018

The Trust expects primarily to purchase Senior Loans by assignment from a participant in the original syndicate of lenders or from subsequent assignees of such interests. The purchaser of an assignment typically succeeds to all the rights and obligations under the loan agreement and has the same rights and obligations as the assigning investor. However, assignments through private negotiations may cause the purchaser of an assignment to have different and more limited rights than those held by the assigning investor. The Trust may also purchase participations in the original syndicate making Senior Loans. Such indebtedness may be secured or unsecured. Loan participations typically represent direct participations in a loan to a corporate borrower, and generally are offered by banks or other financial institutions or lending syndicates. The Trust may participate in such syndications, or can buy part of a loan, becoming a part lender. When purchasing loan participations, the Trust assumes the credit risk associated with the corporate Borrower and may assume the credit risk associated with an interposed bank or other financial intermediary. The participation interests in which the Trust intends to invest may not be rated by any Rating Agency.

The Trust may purchase and retain in its portfolio loans where the Borrowers have experienced, or may be perceived to be likely to experience, credit problems, including default, involvement in or recent emergence from bankruptcy reorganization proceedings or other forms of debt restructuring. At times, in connection with the restructuring of a loan either outside of bankruptcy court or in the context of bankruptcy court proceedings, the Trust may determine or be required to accept equity securities or junior debt securities in exchange for all or a portion of a loan.

The Trust may also purchase unsecured loans, other floating-rate debt securities such as notes, bonds and asset-backed securities (such as special purpose trusts investing in bank loans), credit-linked notes, tranches of collateralized loan obligations, investment grade fixed-income debt obligations and money market instruments, such as commercial paper.

Loans are subject to the risk that a court, pursuant to fraudulent conveyance or other similar laws, could subordinate a loan to presently existing or future indebtedness of the borrower, or take other action detrimental to the holders of a loan including, in certain circumstances, invalidating the loans or causing interest previously paid to be returned to the borrower. Any such actions by a court could negatively affect the Trust’s performance. Loans that are secured and senior to other debtholders of a borrower tend to have more favorable loss recovery rates as compared to more junior types of below investment grade debt obligations. Due to their lower place in the borrower’s capital structure and, in some cases, their unsecured status, junior loans involve a higher degree of overall risk than senior loans of the same borrower.

Investing in loans involves the risk of default by the borrower or other party obligated to repay the loan. In the event of insolvency of the borrower or other obligated party, the Trust may be treated as a general creditor of such entity unless it has rights that are senior to that of other creditors or secured by specific collateral or assets of the borrower. Fixed rate loans are also subject to the risk that their value will decline in a rising interest rate environment. This risk is mitigated for floating-rate loans, where the interest rate payable on the loan resets periodically by reference to a base lending rate.

Many loans in which the Trust will invest may not be rated by a Rating Agency, will not be registered with the SEC or any state securities commission and will not be listed on any national securities exchange. In evaluating the creditworthiness of Borrowers, the Adviser will consider, and may rely in part, on analyses performed by others. Borrowers may have outstanding debt obligations that are rated below investment grade by a Rating Agency. Many of the loans held by the Trust will have been assigned ratings below investment grade by Rating Agencies. In the event loans are not rated, they are likely to be the equivalent of below investment grade quality. Because of the protective features of Senior Loans, the Adviser believes, based on its experience, that Senior Loans tend to have more favorable loss recovery rates as compared to more junior types of below investment grade debt obligations.

U.S. federal securities laws afford certain protections against fraud and misrepresentation in connection with the offering or sale of a security, as well as against manipulation of trading markets for securities. The typical practice of a lender in relying exclusively or primarily on reports from the borrower may involve the risk of fraud, misrepresentation, or market manipulation by the borrower. It is unclear whether U.S. federal securities law protections are available to an investment in a loan. In certain circumstances, loans may not be deemed to be securities, and in the event of fraud or misrepresentation by a borrower, lenders may not have the protection of the anti-fraud provisions of the federal securities laws. However, contractual provisions in the loan documents may offer some protections, and lenders may also avail themselves of common-law fraud protections under applicable state law.

In addition to the risks generally associated with debt instruments, such as credit, market, interest rate and liquidity risks, loans are also subject to the risk that the value of any collateral securing a loan may decline, be insufficient to meet the obligations of the borrower or be difficult to liquidate. The specific collateral used to secure a loan may decline in value or become illiquid, which would adversely affect the loan’s value. The Trust’s access to collateral may be limited by bankruptcy, other insolvency laws or by the type of loan the Trust has purchased. For example, if the Trust purchases a participation instead of an assignment, it would not have direct access to collateral of the borrower. As a result, a floating rate loan may not be fully collateralized and can decline significantly in value. Additionally, collateral on loan instruments may not be readily liquidated, and there is no assurance that the liquidation of such assets will satisfy a borrower’s obligations under the investment.

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When interest rates decline, the value of a fund invested in fixed-rate obligations can be expected to rise. Conversely, when interest rates rise, the value of a fund invested in fixed-rate obligations can be expected to decline. Although changes in prevailing interest rates can be expected to cause some fluctuations in the value of Senior Loans (due to the fact that floating-rates on Senior Loans only reset periodically), the value of Senior Loans is less sensitive to changes in market interest rates than fixed-rate instruments. As a result, the Adviser expects the Trust’s policy of investing a portion of its assets in floating-rate Senior Loans will make the Trust less volatile and less sensitive to changes in market interest rates than if the Trust invested exclusively in fixed-rate obligations. Similarly, a sudden and significant increase in market interest rates may cause a decline in the value of these investments and in the Trust’s net asset value. Other factors (including, but not limited to, rating downgrades, credit deterioration, a large downward movement in stock prices, a disparity in supply and demand of certain Senior Loans and other securities or market conditions that reduce liquidity) can reduce the value of Senior Loans and other debt obligations, impairing the Trust’s net asset value.

Although the overall size and number of participants in the market for loans has grown over the past decade, loans continue to trade in a private, unregulated inter-dealer or inter-bank secondary market. The amount of public information available with respect to Senior Loans will generally be less extensive than that available for registered or exchange listed securities. With limited exceptions, the adviser will take steps intended to ensure that it does not receive material nonpublic information about the issuers of Senior Loans that also issue publicly traded securities. Therefore the adviser may have less information than other investors about certain of the Senior Loans in which it seeks to invest. Purchases and sales of loans are generally subject to contractual restrictions that must be satisfied before a loan can be bought or sold. These restrictions may (i) impede the Trust’s ability to buy or sell loans, (ii) negatively impact the transaction price, (iii) impact the counterparty credit risk borne by the Trust, (iv) impede the Trust’s ability to timely vote or otherwise act with respect to loans, (v) expose the Trust to adverse tax or regulatory consequences and (vi) result in delayed settlement of loan transactions. It may take longer than seven days for transactions in loans to settle. This is partly due to the nature of loans and the contractual restrictions noted above, which require a written assignment agreement and various ancillary documents for each transfer, and frequently require discretionary consents from both the borrower and the administrative agent. In light of the foregoing, the Trust may hold cash, sell securities or temporarily borrow from banks or other lenders to meet short-term liquidity needs due to the extended loan settlement process.

The Adviser uses an independent pricing service to value most loans and other debt securities at their market value. The Adviser may use the fair value method to value loans or other securities if a security or a loan is not priced by a pricing service, a pricing service’s price is deemed unreliable, or if events occur after the close of a securities market (usually a foreign market) and before the Trust values its assets would materially affect net asset value. A security that is fair valued may be valued at a price higher or lower than actual market quotations or the value determined by other funds using their own fair valuation procedures. Because foreign securities trade on days when the Common Shares are not priced, net asset value can change at times when Common Shares cannot be sold.

ADDITIONAL INVESTMENT PRACTICES

Second Lien Loans and Debt Securities. The Trust may invest in loans and other debt securities that have the same characteristics as Senior Loans except that such loans are second in lien priority rather than first. Such “second lien” loans and securities like Senior Loans typically have adjustable floating-rate interest payments. Accordingly, the risks associated with “second lien” loans are higher than the risks of loans with first priority over the collateral. In the event of default on a “second lien” loan, the first priority lien holder has first claim to the underlying collateral of the loan. It is possible, that no collateral value would remain for the second priority lien holder and therefore result in a loss of investment to the Trust.

Collateralized Loan Obligations (“CLOs”). The Trust may invest in certain asset-backed securities as discussed below. Asset-backed securities are payment claims that are securitized in the form of negotiable paper that is issued by a financing company (generically called a Special Purpose Vehicle or “SPV”). These securitized payment claims are, as a rule, corporate financial assets brought into a pool according to specific diversification rules. The SPV is a company founded solely for the purpose of securitizing these claims and its only asset is the risk arising out of this diversified asset pool. On this basis, marketable securities are issued which, due to the diversification of the underlying risk, generally represent a lower level of risk than the original assets. The redemption of the securities issued by the SPV takes place at maturity out of the cash flow generated by the collected claims.

A CLO is a structured credit security issued by an SPV that was created to reapportion the risk and return characteristics of a pool of assets. The assets, typically Senior Loans, are used as collateral supporting the various debt tranches issued by the SPV. The key feature of the CLO structure is the prioritization of the cash flows from a pool of debt securities among the several classes of CLO holders, thereby creating a series of obligations with varying rates and maturities appealing to a wide range of investors. CLOs generally are secured by an assignment to a trustee under the indenture

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pursuant to which the bonds are issued of collateral consisting of a pool of debt instruments, usually, non-investment grade bank loans. Payments with respect to the underlying debt securities generally are made to the trustee under the indenture. CLOs are designed to be retired as the underlying debt instruments are repaid. In the event of sufficient early prepayments on such debt instruments, the class or series of CLO first to mature generally will be retired prior to maturity. Therefore, although in most cases the issuer of CLOs will not supply additional collateral in the event of such prepayments, there will be sufficient collateral to secure their priority with respect to other CLO tranches that remain outstanding. The credit quality of these securities depends primarily upon the quality of the underlying assets, their priority with respect to other CLO tranches and the level of credit support and/or enhancement provided.

The underlying assets (e.g., loans) are subject to prepayments which shorten the securities’ weighted average maturity and may lower their return. If the credit support or enhancement is exhausted, losses or delays in payment may result if the required payments of principal and interest are not made. The value of these securities also may change because of changes in market value, that is changes in the market’s perception of the creditworthiness of the servicing agent for the pool, the originator of the pool, or the financial institution or fund providing the credit support or enhancement. The Trust will indirectly bear any management fees and expenses incurred by a CLO.

Collateralized Debt Obligations (“CDOs”). The Trust may invest in CDOs. A CDO is a structured credit security issued by an SPV that was created to reapportion the risk and return characteristics of a pool of assets. The assets, typically non-investment grade bonds, leveraged loans, and other asset-backed obligations, are used as collateral supporting the various debt and equity tranches issued by the SPV. The key feature of the CDO structure is the prioritization of the cash flows from a pool of debt securities among the several classes of CDO holders, thereby creating a series of obligations with varying rates and maturities appealing to a wide range of investors. CDOs generally are secured by an assignment to a trustee under the indenture pursuant to which the bonds are issued of collateral consisting of a pool of debt securities, usually, non-investment grade bonds. Payments with respect to the underlying debt securities generally are made to the trustee under the indenture. CDOs are designed to be retired as the underlying debt securities are repaid. In the event of sufficient early prepayments on such debt securities, the class or series of CDO first to mature generally will be retired prior to maturity. Therefore, although in most cases the issuer of CDOs will not supply additional collateral in the event of such prepayments, there will be sufficient collateral to secure CDOs that remain outstanding. The credit quality of these securities depends primarily upon the quality of the underlying assets and the level of credit support and/or enhancement provided. CDOs operate similarly to CLOs and are subject to the same inherent risks.

Foreign Securities. The Trust may invest in Senior Loans and other debt securities of non-U.S. issuers. Investment in securities of non-U.S. issuers involves special risks, including that non-U.S. issuers may be subject to less rigorous accounting and reporting requirements than U.S. issuers, less rigorous regulatory requirements, differing legal systems and laws relating to creditors’ rights, the potential inability to enforce legal judgments and the potential for political, social and economic adversity. The willingness and ability of sovereign issuers to pay principal and interest on government securities depends on various economic factors, including among others the issuer’s balance of payments, overall debt level, and cash flow considerations related to the availability of tax or other revenues to satisfy the issuer’s obligations. The securities of some foreign issuers are less liquid and at times more volatile than securities of comparable U.S. issuers. Foreign settlement procedures and trade regulations may involve certain risks (such as delay in the payment or delivery of securities and interest or in the recovery of assets held abroad) and expenses not present in the settlement of domestic investments. Investments may include securities issued by the governments of lesser-developed countries, which are sometimes referred to as “emerging markets.” There may be a possibility of nationalization or expropriation of assets, imposition of currency exchange controls, confiscatory taxation, political or financial instability, armed conflict and diplomatic developments which could affect the value of the Trust’s investments in certain foreign countries. Foreign issuers may become subject to sanctions imposed by the United States or another country, which could result in the immediate freeze of the foreign issuers’ assets or securities. The imposition of such sanctions could impair the market value of the securities of such foreign issuers and limit the Trust’s ability to buy, sell, receive or deliver the securities. Trading in certain foreign markets is also subject to liquidity risks.

The value of foreign assets and currencies as measured in U.S. dollars may be affected favorably or unfavorably by changes in foreign currency rates and exchange control regulations, application of foreign tax laws (including withholding tax), governmental administration of economic or monetary policies (in this country or abroad), and relations between nations and trading. Foreign currencies also are subject to settlement, custodial and other operational risks. Currency exchange rates can be affected unpredictably by intervention, or the failure to intervene, by U.S. or foreign governments or central banks or by currency controls or political developments in the United States or abroad. If the U.S. dollar rises in value relative to a foreign currency, a security denominated in that foreign currency will be worth less in U.S. dollars. If the U.S. dollar decreases in value relative to a foreign currency, a security denominated in that foreign currency will be worth more in U.S. dollars. A devaluation of a currency by a country’s government or banking authority will have a significant impact on the value of any investments denominated in that currency. Costs are incurred in connection with conversions between currencies.

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Corporate Bonds and Other Debt Securities. The Trust may invest in a wide variety of bonds, debentures and similar debt securities of varying maturities and durations issued by corporations and other business entities, including limited liability companies. Debt securities in which the Trust may invest may pay fixed or variable rates of interest. Bonds and other debt securities generally are issued by corporations and other issuers to borrow money from investors. The issuer pays the investor a fixed or variable rate of interest and normally must repay the amount borrowed on or before maturity. Certain debt securities are “perpetual” in that they have no maturity date. The Trust may invest in bonds and other debt securities of any quality. As discussed below, Non-Investment Grade Bonds, commonly known as “junk bonds,” are considered to be predominantly speculative in nature because of the credit risk of the issuers.

Non-Investment Grade Bonds. As indicated above, Non-Investment Grade Bonds are those rated lower than investment grade (i.e., bonds rated lower than Baa3 by Moody’s and lower than BBB- by S&P and Fitch) or are unrated and of comparable quality as determined by the Adviser. Non-Investment Grade Bonds rated BB and Ba have speculative characteristics, while lower rated Non-Investment Grade Bonds are predominantly speculative.

The Trust may hold securities that are unrated or in the lowest rating categories (rated C by Moody’s or D by S&P or Fitch). Bonds rated C by Moody’s are regarded as having extremely poor prospects of ever attaining any real investment standing. Bonds rated D by S&P or Fitch are in payment default or a bankruptcy petition has been filed and debt service payments are jeopardized. In order to enforce its rights with defaulted securities, the Trust may be required to retain legal counsel and/or a financial adviser. This may increase the Trust’s operating expenses and adversely affect net asset value.

The credit quality of most securities held by the Trust reflects a greater than average possibility that adverse changes in the financial condition of an issuer, or in general economic conditions, or both, may impair the ability of the issuer to make payments of interest and principal. The inability (or perceived inability) of issuers to make timely payment of interest and principal would likely make the values of securities held by the Trust more volatile and could limit the Trust’s ability to sell its securities at favorable prices. In the absence of a liquid trading market for securities held by it, the Trust may have difficulties determining the fair market value of such securities.

Although the Adviser considers security ratings when making investment decisions, it performs its own credit and investment analysis and does not rely primarily on the ratings assigned by the rating agencies. In evaluating the quality of a particular investment, whether rated or unrated, the Adviser will normally take into consideration, among other things, the issuer’s financial resources and operating history, its sensitivity to economic conditions and trends, the ability of its management, its debt maturity schedules and borrowing requirements, and relative values based on anticipated cash flow, interest and asset coverage, and earnings prospects. Credit ratings are based largely on the issuer’s historical financial condition and a rating agency’s investment analysis at the time of rating: the rating assigned to any particular security is not necessarily a reflection of the issuer’s current financial condition. The rating assigned to a security or other instrument by a rating agency does not reflect assessment of the volatility of its market value or liquidity. Credit quality in the sectors of the market can change from time to time, and recently issued credit ratings may not fully reflect the actual risks posed by a particular investment.

Because of the greater number of investment considerations involved in investing in investments that receive lower ratings, investing in lower rated investments depends more on the Adviser’s judgment and analytical abilities than may be the case for investing in investments with higher ratings. While the Adviser will attempt to reduce the risks of investing in lower rated or unrated securities through active portfolio management, diversification, credit analysis and attention to current developments and trends in the economy and the financial markets, there can be no assurance that a broadly diversified portfolio of such securities would substantially lessen the risks of defaults brought about by an economic downturn or recession.

Investments in obligations rated below investment grade and comparable unrated securities (sometimes referred to as “junk”) generally entail greater economic, credit and liquidity risks than investment grade securities. Lower rated investments have speculative characteristics because of the credit risk associated with their issuers. Changes in economic conditions or other circumstances typically have a greater effect on the ability of issuers of lower rated investments to make principal and interest payments than they do on issuers of higher rated investments. An economic downturn generally leads to a higher non-payment rate, and a lower rated investment may lose significant value before a default occurs. Lower rated investments generally are subject to greater price volatility and illiquidity than higher rated investments.

The Trust’s high yield securities may have fixed or variable principal payments and all types of interest rate and dividend payment and reset terms, including fixed rate, adjustable rate, zero coupon, contingent, deferred, and payment in kind features.

Convertible Securities. The Trust may invest in convertible securities. A convertible security is a bond, debenture, note, preferred security, or other security that entitles the holder to acquire common stock or other equity securities of the same or a different issuer. A convertible security entitles the holder to receive interest paid or accrued or dividends paid until

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the convertible security matures or is redeemed, converted or exchanged. Before conversion, convertible securities have characteristics similar to nonconvertible income securities. The Trust may invest in convertible securities of any rating.

Holders of convertible securities generally have a claim on the assets of the issuer prior to the common stockholders but may be subordinated to other debt securities of the same issuer. Certain convertible debt securities may provide a put option to the holder, which entitles the holder to cause the securities to be redeemed by the issuer at a premium over the stated principal amount of the debt securities under certain circumstances. Certain convertible securities may include loss absorption characteristics that make the securities more debt-like. This is particularly true of convertible securities issued by companies in the financial services sector.

The value of a convertible security may be influenced by changes in interest rates, with investment value declining as interest rates increase and increasing as interest rates decline. The credit standing of the issuer and other factors also may have an effect on the convertible security’s investment value. A convertible security may be subject to redemption at the option of the issuer at a price established in the convertible security’s governing instrument.

Government Securities. U.S. Government securities include (1) U.S. Treasury obligations, which differ in their interest rates, maturities and times of issuance: U.S. Treasury bills (maturities of one year or less), U.S. Treasury notes (maturities of one year to ten years) and U.S. Treasury bonds (generally maturities of greater than ten years) and (2) obligations issued or guaranteed by U.S. Government agencies and instrumentalities that are supported by any of the following: (a) the full faith and credit of the U.S. Treasury, (b) the right of the issuer to borrow an amount limited to a specific line of credit from the U.S. Treasury, (c) discretionary authority of the U.S. Government to purchase certain obligations of the U.S. Government agency or instrumentality or (d) the credit of the agency or instrumentality. The Trust may also invest in any other security or agreement collateralized or otherwise secured by U.S. Government securities. Agencies and instrumentalities of the U.S. Government include but are not limited to: Federal Land Banks, Federal Financing Banks, Banks for Cooperatives, Federal Intermediate Credit Banks, Farm Credit Banks, Federal Home Loan Banks, Federal Home Loan Mortgage Corporation, Federal National Mortgage Association, Government National Mortgage Association, Student Loan Marketing Association, United States Postal Service, Small Business Administration, Tennessee Valley Authority and any other enterprise established or sponsored by the U.S. Government. Because the U.S. Government generally is not obligated to provide support to its instrumentalities, the Trust will invest in obligations issued by these instrumentalities only if the Adviser determines that the credit risk with respect to such obligations is minimal.

The principal of and/or interest on certain U.S. Government securities which may be purchased by the Trust could be (a) payable in foreign currencies rather than U.S. dollars or (b) increased or diminished as a result of changes in the value of the U.S. dollar relative to the value of foreign currencies. The value of such portfolio securities may be affected favorably by changes in the exchange rate between foreign currencies and the U.S. dollar.

Because of their high credit quality and market liquidity, U.S. Treasury and Agency Securities generally provide a lower current return than obligations of other issuers. While the U.S. Government has provided financial support to Fannie Mae and Freddie Mac in the past, but there can be no assurance that it will support these or other government-sponsored enterprises in the future.

Commercial Paper. Commercial paper represents short-term unsecured promissory notes issued in bearer form by corporations such as banks or bank holding companies and finance companies. The rate of return on commercial paper may be linked or indexed to the level of exchange rates between the U.S. dollar and a foreign currency or currencies.

Forward Commitments and When-Issued Securities. The Trust may purchase securities on a “forward commitment” or “when-issued” basis (meaning securities are purchased or sold with payment and delivery taking place in the future). In such a transaction, the Trust is securing what is considered to be an advantageous price and yield at the time of entering into the transaction.

The yield on a comparable security when the transaction is consummated may vary from the yield on the security at the time that the forward commitment or when-issued transaction was made. From the time of entering into the transaction until delivery and payment is made at a later date, the securities that are the subject of the transaction are subject to market fluctuations. In forward commitment or when-issued transactions, if the seller or buyer, as the case may be, fails to consummate the transaction, the counterparty may miss the opportunity of obtaining a price or yield considered to be advantageous. Forward commitment or when-issued transactions may be expected to occur a month or more before delivery is due. No payment or delivery is made, however, until payment is received or delivery is made from the other party to the transaction. These transactions may create leverage in the Trust.

Restricted and Illiquid Securities. The Trust may invest without limitation in Senior Loans and other securities for which there is no readily available trading market or are otherwise illiquid. Illiquid securities include securities legally restricted as to resale, such as commercial paper issued pursuant to Section 4(a)(2) of the 1933 Act, and securities eligible for resale pursuant to Rule 144A thereunder. Section 4(a)(2) and Rule 144A securities may, however, be treated as liquid by the Adviser after considering factors such as trading activity, availability of market quotations and number of dealers willing to purchase the security.

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It may be difficult to sell such securities at a price representing the fair value until such time as such securities may be sold publicly. Where registration is required, a considerable period may elapse between a decision to sell the securities and the time when it would be permitted to sell. Thus, the Trust may not be able to obtain as favorable a price as that prevailing at the time of the decision to sell. The Trust may incur additional expense when disposing of illiquid securities, including all or a portion of the costs to register the securities. The Trust may also acquire securities through private placements under which it may agree to contractual restrictions on the resale of such securities. Such restrictions might prevent their sale at a time when such sale would otherwise be desirable.

At times, a portion of the Trusts’ assets may be invested in securities as to which the Trust, by itself or together with other accounts managed by the investment adviser and its affiliates, holds a major portion or all of such securities. Restricted and illiquid securities may be difficult to value properly and may involve greater risks than liquid securities. It may be difficult to sell illiquid securities at a price representing fair value until such time as the securities may be sold publicly. Under adverse market or economic conditions or in the event of adverse changes in the financial condition of the issuer, the Trust could find it more difficult to sell such securities when the investment adviser believes it advisable to do so or may be able to sell such securities only at prices lower than if such securities were more widely held. It also may be more difficult to determine the fair value of such securities for purposes of computing the Trust’s net asset value. Even if determined to be liquid, holdings of restricted securities may increase the level of Trust illiquidity if eligible buyers become uninterested in purchasing them. Restricted securities may involve a high degree of business and financial risk which may result in substantial losses.

Derivatives. Generally, derivatives can be characterized as financial instruments whose performance is derived at least in part from the performance of an underlying reference instrument. Derivative instruments may be acquired in the United States or abroad consistent with the Trust’s investment strategy and may include the various types of exchange-traded and over-the-counter (“OTC”) instruments described herein and other instruments with substantially similar characteristics and risks. Trust obligations created pursuant to derivative instruments may give rise to leverage, which would subject the Trust to the requirements described under “Asset Coverage” in the Trust’s SAI. The Trust may invest in a derivative transaction if it is permitted to own, invest in, or otherwise have economic exposure to the reference instrument. A reference instrument could be a security, instrument, index, currency, commodity, economic indicator or event (“reference instruments”). As described more specifically below, the Trust may purchase or sell derivative instruments (which are instruments that derive their value from another instrument, security or index) to seek to hedge against fluctuations in securities prices or interest rates or for the purpose of leveraging the Trust. The Trust’s transactions in derivatives instruments may include the purchase or sale of futures contracts on securities, indices and other financial instruments, credit-linked notes, tranches of collateralized loan obligations and/or collateralized debt obligations, options on futures contracts, and exchange-traded and over-the-counter options on securities or indices, index-linked securities, and interest rate, total return and credit default swaps. The Trust may trade in the specific types and/or combinations of derivative transactions listed below.

Derivative instruments are subject to a number of risks, including adverse or unexpected movements in the price of the reference instrument, and counterparty, credit, interest rate, liquidity, market, tax and leverage risks. In addition, derivatives also involve the risk that changes in their value may not correlate perfectly with the assets, rates, indices or instruments they are designed to hedge or closely track. Use of derivative instruments may cause the realization of higher amounts of short-term capital gains (generally taxed at ordinary income tax rates) than if such instruments had not been used. Success in using derivative instruments to hedge portfolio assets depends on the degree of price correlation between the derivative instruments and the hedged asset. Imperfect correlation may be caused by several factors, including temporary price disparities among the trading markets for the derivative instrument, the reference instrument and the Trust’s assets. To the extent that a derivative instrument is intended to hedge against an event that does not occur, the Trust may realize losses.

OTC derivative instruments involve an additional risk in that the issuer or counterparty may fail to perform its contractual obligations. Some derivative instruments are not readily marketable or may become illiquid under adverse market conditions. In addition, during periods of market volatility, an option or commodity exchange or swap execution facility or clearinghouse may suspend or limit trading in an exchange-traded derivative instrument, which may make the contract temporarily illiquid and difficult to price. Commodity exchanges may also establish daily limits on the amount that the price of a futures contract or futures option can vary from the previous day’s settlement price. Once the daily limit is reached, no trades may be made that day at a price beyond the limit. This may prevent the closing out of positions to limit losses. The staff of the SEC takes the position that certain purchased OTC options, and assets used as cover for written OTC options, are illiquid. The ability to terminate OTC derivative instruments may depend on the cooperation of the counterparties to such contracts. For thinly traded derivative instruments, the only source of price quotations may be the selling dealer or counterparty. In addition, certain provisions of the Code limit the use of derivative instruments. Derivatives permit the

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Trust to increase or decrease the level of risk, or change the character of the risk, to which its portfolio is exposed in much the same way as the Trust can increase or decrease the level of risk, or change the character of the risk, of its portfolio by making investments in specific securities. There can be no assurance that the use of derivative instruments will benefit the Trust.

The regulation of the U.S. and non-U.S. derivatives markets has undergone substantial change in recent years. In particular, the Dodd-Frank Wall Street Reform and Consumer Protection Act (the “Dodd-Frank Act”) and related regulations require many derivatives to be cleared and traded on an exchange, expand entity registration requirements, impose business conduct requirements on counterparties, and impose other regulatory requirements that will continue to change derivatives markets as regulations are implemented. Additional future regulation of the derivatives markets may make the use of derivatives more costly, may limit the availability or reduce the liquidity of derivatives, and may impose limits or restrictions on the counterparties with which the Trust engages in derivative transactions. Trust management cannot predict the effects of any new governmental regulation that may be implemented, and future regulation may impair the effectiveness of the Trust’s derivative transactions and its ability to achieve its investment objectives.

Futures Contracts. Futures are standardized, exchange-traded contracts. Futures contracts on securities obligate a purchaser to take delivery, and a seller to make delivery, of a specific amount of the financial instrument called for in the contract at a specified future date at a specified price. An index futures contract obligates the purchaser to take, and a seller to deliver, an amount of cash equal to a specific dollar amount times the difference between the value of a specific index at the close of the last trading day of the contract and the price at which the agreement is made. No physical delivery of the underlying securities in the index is made. It is the practice of holders of futures contracts to close out their positions on or before the expiration date by use of offsetting contract positions, and physical delivery of financial instruments or delivery of cash, as applicable, is thereby avoided. An option on a futures contract gives the holder the right to enter into a specified futures contract.

Credit-Linked Notes. The Trust may invest in credit-linked notes (“CLN”) for risk management purposes, including diversification. A CLN is a type of hybrid instrument in which a special purpose entity issues a structured note (the “Note Issuer”) with respect to which the reference instrument is a single bond, a portfolio of bonds or the unsecured credit of an issuer, in general (each a “Reference Credit”). The purchaser of the CLN (the “Note Purchaser”) invests a par amount and receives a payment during the term of the CLN that equals a fixed or floating rate of interest equivalent to a high rated funded asset (such as a bank certificate of deposit) plus an additional premium that relates to taking on the credit risk of the Reference Credit. Upon maturity of the CLN, the Note Purchaser will receive a payment equal to: (i) the original par amount paid to the Note Issuer, if there is no occurrence of a designated event of default, restructuring or other credit event (each a “Credit Event”) with respect to the issuer of the Reference Credit; or (ii) the market value of the Reference Credit, if a Credit Event has occurred. Depending upon the terms of the CLN, it is also possible that the Note Purchaser may be required to take physical delivery of the Reference Credit in the event of Credit Event. Most CLNs use a corporate bond (or a portfolio of corporate bonds) as the Reference Credit. However, almost any type of fixed income security (including foreign government securities), index or derivative contract (such as a credit default swap) can be used as the Reference Credit.

Swaps. Swap contracts may be purchased or sold to hedge against fluctuations in securities prices, interest rates or market conditions, to change the duration of the overall portfolio, or to mitigate default risk. In a standard “swap” transaction, two parties agree to exchange the returns (or differentials in rates of return) to be exchanged or “swapped” between the parties, which returns are calculated with respect to a “notional amount,” i.e., the return on or increase in value of a particular dollar amount invested at a particular interest rate or in a “basket” of securities representing a particular index.

Interest Rate Swaps. The Trust will enter into interest rate and total return swaps only on a net basis, i.e., the two payment streams are netted out, with the Trust receiving or paying, as the case may be, only the net amount of the two payments. Interest rate swaps involve the exchange by the Trust with another party of their respective commitments to pay or receive interest (e.g., an exchange of fixed rate payments for floating-rate payments). The Trust will only enter into interest rate swaps on a net basis. If the other party to an interest rate swap defaults, the Trust’s risk of loss consists of the net amount of payments that the Trust is contractually entitled to receive. The net amount of the excess, if any, of the Trust’s obligations over its entitlements will be maintained in a segregated account by the Trust’s custodian. The Trust will not enter into any interest rate swap unless the claims-paying ability of the other party thereto is considered to be investment grade by the Adviser. If there is a default by the other party to such a transaction, the Trust will have contractual remedies pursuant to the agreements related to the transaction. These instruments are traded in the over-the-counter market.

The Trust may use interest rate swaps for risk management purposes only and not as a speculative investment and would typically use interest rate swaps to shorten the average interest rate reset time of the Trust’s holdings. Interest rate swaps involve the exchange by the Trust with another party of their respective commitments to pay or receive interest (e.g., an exchange of fixed rate payments for floating-rate payments). The use of interest rate swaps is a

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highly specialized activity which involves investment techniques and risks different from those associated with ordinary portfolio securities transactions. If the Adviser is incorrect in its forecasts of market values, interest rates and other applicable factors, the investment performance of the Trust would be unfavorably affected.

Total Return Swaps. As stated above, the Trust will enter into total return swaps only on a net basis. A total return swap is a contract in which one party agrees to make periodic payments to another party based on the change in market value of a referenced asset during the specified period, in return for periodic payments from the other party that are based on a fixed or variable interest rate or the total return of the referenced asset or another referenced asset. Total return swap agreements may be used to obtain exposure to a security or market without owning or taking physical custody of such security or investing directly in such market.

Credit Default Swaps. The Trust may enter into credit default swap contracts for risk management purposes, including diversification. When the Trust is the buyer of a credit default swap contract, the Trust is entitled to receive the par (or other agreed-upon) value of a referenced debt obligation from the counterparty to the contract in the event of a default by a third party, such as a U.S. or foreign corporate issuer, on the debt obligation. In return, the Trust would pay the counterparty a periodic stream of payments over the term of the contract provided that no event of default has occurred. If no default occurs, the Trust would have spent the stream of payments and received no benefit from the contract. When the Trust is the seller of a credit default swap contract, it receives the stream of payments, but is obligated to pay upon default of the referenced debt obligation. As the seller, the Trust would effectively add leverage to its portfolio because, in addition to its total net assets, the Trust would be subject to investment exposure on the notional amount of the swap. These transactions involve certain risks, including the risk that the seller may be unable to fulfill the transaction.

Credit default swap agreements (“CDS”) enable the Trust to buy or sell credit protection on an individual issuer or basket of issuers (i.e., the reference instrument). The Trust may enter into CDS to gain or short exposure to a reference instrument. Long CDS positions are utilized to gain exposure to a reference instrument (similar to buying the instrument) and are akin to selling insurance on the instrument. Short CDS positions are utilized to short exposure to a reference instrument (similar to shorting the instrument) and are akin to buying insurance on the instrument.

Under a CDS, the protection “buyer” in a credit default contract is generally obligated to pay the protection “seller” an upfront or a periodic stream of payments over the term of the contract, provided that no credit event, such as a default, on a reference instrument has occurred. If a credit event occurs, the seller generally must pay the buyer the “par value” (full notional value) of the reference instrument in exchange for an equal face amount of the reference instrument described in the swap, or the seller may be required to deliver the related net cash amount, if the swap is cash settled. If the Trust is a buyer and no credit event occurs, the Trust may recover nothing if the swap is held through its termination date. As a seller, the Trust generally receives an upfront payment or a fixed rate of income throughout the term of the swap provided that there is no credit event. The Trust’s obligations under a CDS will be accrued daily (offset against any amounts owed to the Trust).

In response to market events, federal and certain state regulators have proposed regulation of the CDS market. These regulations may limit the Trust’s ability to use CDS and/or the benefits of CDS. CDS may be difficult to value and generally pay a return to the party that has paid the premium only in the event of an actual default by the issuer of the underlying obligation (as opposed to a credit downgrade or other indication of financial difficulty). The Trust may have difficulty, be unable or may incur additional costs to acquire any securities or instruments it is required to deliver under a CDS. The Trust many have limited ability to eliminate its exposure under a CDS either by assignment or other disposition, or by entering into an offsetting swap agreement. The Trust also may have limited ability to eliminate its exposure under a CDS if the reference instrument has declined in value.

Futures and Options on Futures. The Trust may purchase and sell various kinds of financial futures contracts and options thereon to seek to hedge against changes in interest rates or for other risk management purposes. Futures contracts may be based on various debt securities and securities indices. Such transactions involve a risk of loss or depreciation due to unanticipated adverse changes in securities prices, which may exceed the Trust’s initial investment in these contracts. The Trust will only purchase or sell futures contracts or related options in compliance with the rules of the CFTC. These transactions involve transaction costs. There can be no assurance that Eaton Vance’s use of futures will be advantageous to the Trust. Rating Agency guidelines on any preferred shares issued by the Trust, including APS, may limit use of these transactions.

Options. Options may be traded on an exchange and OTC. By buying a put option on a particular instrument, the Trust acquires a right to sell the underlying instrument at the exercise price. By buying a put option on an index, the Trust acquires a right to receive the cash difference between the strike price of the option and the index price at expiration. A purchased put position also typically can be sold at any time by selling at prevailing market prices. Purchased put options generally are expected to limit the Trust's risk of loss through a decline in the market value of the underlying security or index until the put option expires. When buying a put, the Trust pays a premium to the seller of the option. If the price of the underlying security or index is above the exercise price of the option as of the option valuation date, the option expires worthless and the Trust will not be able to recover the option premium paid to the seller. The Trust may purchase uncovered put options on securities, meaning it will not own the securities underlying the option.

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The Trust may also write (i.e., sell) put options. The Trust will receive a premium for selling a put option, which may increase the Trust's return. In selling a put option on a security, the Trust has the obligation to buy the security at an agreed upon price if the price of such instrument decreases below the exercise price. By selling a put option on an index, the Trust has an obligation to make a payment to the buyer to the extent that the value of the index decreases below the exercise price as of the option valuation date. If the value of the underlying security or index on the option’s expiration date is above the exercise price, the option will generally expire worthless and the Trust, as option seller, will have no obligation to the option holder.

The Trust may purchase call options. By purchasing a call option on a security, the Trust has the right to buy the security at the option’s exercise price. By buying a call option on an index, the Trust acquires the right to receive the cash difference between the market price of the index and strike price at expiration. Call options typically can be exercised any time prior to option maturity or, sold at the prevailing market price.

The Trust may also write (i.e., sell) a call option on a security or index in return for a premium. A call written on a security obligates the Trust to deliver the underlying security at the option exercise price. Written index call options obligate the Trust to make a cash payment to the buyer at expiration if the market price of the index is above the option strike price. Calls typically can also be bought back by the Trust at prevailing market prices and the Trust also may enter into closing purchase transactions with respect to written call options.

The Trust’s options positions are marked to market daily. The value of options is affected by changes in the value and dividend rates of their underlying instruments, changes in interest rates, changes in the actual or perceived volatility of the relevant index or market and the remaining time to the options’ expiration, as well as trading conditions in the options market. The hours of trading for options may not conform to the hours during which the underlying instruments are traded. To the extent that the options markets close before markets for the underlying instruments, significant price and rate movements can take place in the markets that would not be reflected concurrently in the options markets.

The Trust's ability to sell the instrument underlying a call option may be limited while the option is in effect unless the Trust enters into a closing purchase transaction. Uncovered call options have speculative characteristics and are riskier than covered call options because there is no underlying instrument held by the Trust that can act as a partial hedge. As the seller of a covered call option or an index call option, the Trust may forego, during the option’s life, the opportunity to profit from increases in the market value of the underlying instrument covering the call option above the sum of the premium received by the Trust and the exercise price of the call. The Trust also retains the risk of loss, minus the option premium received, should the price of the underlying instrument decline.

Participants in OTC markets are typically not subject to the same credit evaluation and regulatory oversight as are members of “exchange-based” markets. OTC option contracts generally carry greater liquidity risk than exchange-traded contracts. This risk may be increased in times of financial stress, if the trading market for OTC options becomes restricted. The ability of the Trust to transact business with any one or a number of counterparties may increase the potential for losses to the Trust, due to the lack of any independent evaluation of the counterparties or their financial capabilities, and the absence of a regulated market to facilitate settlement of the options.

Counterparty Risk. A financial institution or other counterparty with whom the Trust does business (such as trading or as a derivatives counterparty), or that underwrites, distributes or guarantees any instruments that the Trust owns or is otherwise exposed to, may decline in financial condition and become unable to honor its commitments. This could cause the value of Trust shares to decline or could delay the return or delivery of collateral or other assets to the Trust. Counterparty risk is increased for contracts with longer maturities.

Securities Lending. The Trust may lend its portfolio securities to broker-dealers and other institutional borrowers. During the existence of a loan, the Trust will continue to receive the equivalent of the interest paid by the issuer on the securities loaned, or all or a portion of the interest on investment of the collateral, if any. The Trust may pay lending fees to such borrowers. Loans will only be made to firms that have been approved by the investment adviser, and the investment adviser or the securities lending agent will periodically monitor the financial condition of such firms while such loans are outstanding. Securities loans will only be made when the investment adviser believes that the expected returns, net of expenses, justify the attendant risks. Securities loans currently are required to be secured continuously by collateral in cash, cash equivalents (such as money market instruments) or other liquid securities held by the custodian and maintained in an amount at least equal to the market value of the securities loaned. The Trust may engage in securities lending to generate income. Upon return of the loaned securities, the Trust would be required to return the related collateral to the borrower and may be required to liquidate portfolio securities in order to do so. The Trust may lend up to one-third of the value of its total assets or such other amount as may be permitted by law.

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As with other extensions of credit, there are risks of delay in recovery or even loss of rights in the securities loaned if the borrower of the securities fails financially. To the extent that the portfolio securities acquired with such collateral have decreased in value, it may result in the Trust realizing a loss at a time when it would not otherwise do so. As such, securities lending may introduce leverage into the Trust. The Trust also may incur losses if the returns on securities that it acquires with cash collateral are less than the applicable rebate rates paid to borrowers and related administrative costs.

Borrowings. The Trust may borrow money to the extent permitted under the 1940 Act as interpreted, modified or otherwise permitted by the regulatory authority having jurisdiction. Subject to Rating Agency guidelines regarding the APS and the Trust’s ability to maintain a rating of Aa3 on APS, the Trust may from time to time borrow money to add leverage to the portfolio. Under the 1940 Act, the Trust is not permitted to incur indebtedness, including through the issuance of debt securities, unless immediately thereafter the total asset value of the Trust’s portfolio is at least 300% of the liquidation value of the outstanding indebtedness (i.e., such liquidation value may not exceed 33 1/3% of the Trust’s total assets). The Trust may also borrow money for temporary administrative purposes.

The Trust has entered into a Revolving Credit and Security Agreement (the “Agreement”) with conduit lenders and a bank to allow it to borrow up to $125 million ($100 million prior to September 13, 2018). The proceeds of which were used to invest in accordance with the Trust’s investment practices and to partially redeem the Trust’s APS. Borrowings under the Agreement are secured by the assets of the Trust. Interest is charged at a rate above the conduits’ commercial paper issuance rate and is payable monthly. Under the terms of the Agreement, the Trust also pays a program fee of 0.67% per annum on its outstanding borrowings to administer the facility and a liquidity fee of 0.15% (0.25% if the outstanding loan amount is less than or equal to 60% of the total facility size) per annum on the borrowing limit under the Agreement. Program and liquidity fees for the year ended June 30, 2018 totaled $739,164 and for the three months ended September 30, 2018 totaled $197,384. In connection with the increase in the borrowing limit on September 13, 2018, the Trust paid an additional upfront fee of $12,260 which is being amortized over the remaining term of the Agreement to March 11, 2019. In connection with the renewal of the Agreement in March 2018, the Trust paid an upfront fee of $100,000 that is being amortized to interest expense over a period of one year through March 2019. The Trust is required to maintain certain net asset levels during the term of the Agreement. At September 30, 2018, the Trust had borrowings outstanding under the Agreement of $113 million at an interest rate of 2.21%. Based on the short-term nature of the borrowings under the Agreement and the variable interest rate, the carrying amount of the borrowings at June 30, 2018 approximated its fair value. For the year ended June 30, 2018, the average borrowings under the Agreement and the average interest rate (excluding fees) were $87,202,740 and 1.63%, respectively. For the three months ended September 30, 2018 the average borrowings under the Agreement and the average interest rate (excluding fees) were $92,891,304 and 2.16%, respectively. In addition, the credit facility may in the future be replaced or refinanced by one or more credit facilities having substantially different terms or by the issuance of preferred shares or debt securities.

Repurchase Agreements. The Trust may enter into repurchase agreements (the purchase of a security coupled with an agreement to resell at a higher price) with respect to its permitted investments. A repurchase agreement is the purchase by the Trust of securities from a counterparty in exchange for cash that is coupled with an agreement to resell those securities to the counterparty at a specified date and price. Repurchase agreements that mature in more than seven days will be treated as illiquid. When a repurchase agreement is entered into, the Trust typically receives securities with a value that equals or exceeds the repurchase price, including any accrued interest earned on the agreement. The value of such securities will be marked to market daily, and cash or additional securities will be exchanged between the parties as needed. Except in the case of a repurchase agreement entered into to settle a short sale, the value of the securities delivered to the Trust will be at least equal to repurchase price during the term of the repurchase agreement. The terms of a repurchase agreement entered into to settle a short sale may provide that the cash purchase price paid by the Trust is more than the value of purchased securities that effectively collateralize the repurchase price payable by the counterparty. Since in such a transaction the Trust normally will have used the purchased securities to settle the short sale, the Trust will segregate liquid assets equal to the marked to market value of the purchased securities that it is obligated to return to the counterparty under the repurchase agreement.

In the event of the insolvency of the counterparty to a repurchase agreement, recovery of the repurchase price owed to the Trust may be delayed. In a repurchase agreement, such an insolvency may result in a loss to the extent that the value of the purchased securities decreases during the delay or that value has otherwise not been maintained at an amount equal to the repurchase price. Repurchase agreements may create leverage in the Trust.

Reverse Repurchase Agreements. While the Trust has no current intention to enter into reverse repurchase agreements, the Trust reserves the right to enter into reverse repurchase agreements in the future, at levels that may vary over time. Under a reverse repurchase agreement, the Trust temporarily transfers possession of a portfolio instrument to another party, such as a bank or broker-dealer, in return for cash. At the same time, the Trust agrees to repurchase the instrument at an agreed upon time (normally within seven days) and price, which reflects an interest payment. The Trust may enter into such agreements when it is able to invest the cash acquired at a rate higher than the cost of the agreement, which would increase earned income.

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In the event of the insolvency of the counterparty to a reverse repurchase agreement, recovery of the securities sold by the Trust may be delayed. In a reverse repurchase agreement, the counterparty’s insolvency may result in a loss equal to the amount by which the value of the securities sold by the Trust exceeds the repurchase price payable by the Trust.

When the Trust enters into a reverse repurchase agreement, any fluctuations in the market value of either the securities transferred to another party or the securities in which the proceeds may be invested would affect the market value of the Trust’s assets. As a result, such transactions may increase fluctuations in the market value of the Trust’s assets. While there is a risk that large fluctuations in the market value of the Trust’s assets could affect net asset value, this risk is not significantly increased by entering into reverse repurchase agreements, in the opinion of the Adviser. Because reverse repurchase agreements may be considered to be the practical equivalent of borrowing funds, they constitute a form of leverage. The SEC views reverse repurchase transactions as collateralized borrowings by a fund. Such agreements will be treated as subject to investment restrictions regarding “borrowings.” If the Trust reinvests the proceeds of a reverse repurchase agreement at a rate lower than the cost of the agreement, entering into the agreement will lower the Trust’s yield.

USE OF LEVERAGE AND RELATED RISKS

Generally, leverage involves the use of proceeds from the issuance of preferred shares, borrowed funds or various financial instruments (such as derivatives) to seek to increase a trust’s potential returns. The Trust currently uses leverage created by issuing APS as well as by loans acquired with borrowings. The Trust currently uses leverage created by issuing APS. On June 27, 2001, the Trust issued 2,200 Series A APS and 2,200 Series B APS, with a liquidation preference per share of $25,000 plus accumulated but unpaid dividends. The APS have seniority over the Common Shares. On September 23, 2016, the Trust repurchased 968 Series A APS and 968 Series B APS. On September 14, 2018, the Trust repurchased 480 Series A APS and 480 Series B APS. In addition, in connection with this repurchase, the Trust increased its borrowing limits under its Revolving Credit and Security Agreement, as amended (the “Agreement”) with conduit lenders and a bank to allow it to borrow up to $125 million ($100 million prior to September 13, 2018). The proceeds of which were used to invest in accordance with the Trust’s investment practices and to partially redeem the Trust’s APS. Borrowings under the Agreement are secured by the assets of the Trust. Interest is charged at a rate above the conduits’ commercial paper issuance rate and is payable monthly. Under the terms of the Agreement, the Trust also pays a program fee of 0.67% per annum on its outstanding borrowings to administer the facility and a liquidity fee of 0.15% (0.25% if the outstanding loan amount is less than or equal to 60% of the total facility size) per annum on the borrowing limit under the Agreement. Program and liquidity fees for the year ended June 30, 2018 totaled $739,164 and for the three months ended September 30, 2018 totaled $197,384. In connection with the increase in the borrowing limit on September 13, 2018, the Trust paid an additional upfront fee of $12,260 which is being amortized over the remaining term of the Agreement to March 11, 2019. In connection with the renewal of the Agreement in March 2018, the Trust paid an upfront fee of $100,000 that is being amortized to interest expense over a period of one year through March 2019. The Trust is required to maintain certain net asset levels during the term of the Agreement. As of September 30, 2018, the Trust had $113 million in outstanding borrowings, at an interest rate of 2.21%, in addition to outstanding APS. The Adviser anticipates that the use of leverage (from such issuance of APS and any borrowings) may result in higher income to Common Shareholders over time. Use of financial leverage creates an opportunity for increased income but, at the same time, creates special risks. There can be no assurance that a leveraging strategy will be successful.

The costs of the financial leverage program (from any issuance of preferred shares and any borrowings) are borne by Common Shareholders and consequently result in a reduction of the NAV of Common Shares. During periods in which the Trust is using leverage, the fees paid to Eaton Vance for investment advisory services will be higher than if the Trust did not use leverage because the fees paid will be calculated on the basis of the Trust’s gross assets, including proceeds from the issuance of preferred shares and any borrowings. In this regard, holders of debt or preferred securities do not bear the investment advisory fee. Rather, Common Shareholders bear the portion of the investment advisory fee attributable to the assets purchased with the proceeds, which means that Common Shareholders effectively bear the entire advisory fee.

Leverage creates risks for holders of the Common Shares, including the likelihood of greater volatility of NAV and market price of the Common Shares. There is a risk that fluctuations in the distribution rates on any outstanding preferred shares may adversely affect the return to the holders of the Common Shares. If the income from the investments purchased with the proceeds of leverage is not sufficient to cover the cost of leverage, the return on the Trust will be less than if leverage had not been used, and, therefore, the amount available for distribution to Common Shareholders will be reduced. The Adviser in its best judgment nevertheless may determine to maintain the Trust’s leveraged position if it deems such action to be appropriate in the circumstances.

Changes in the value of the Trust’s investment portfolio (including investments bought with the proceeds of leverage) will be borne entirely by the Common Shareholders. If there is a net decrease (or increase) in the value of the Trust’s investment portfolio, the leverage will decrease (or increase) the NAV per Common Share to a greater extent than if the Trust were not leveraged. During periods in which the Trust is using leverage, the fees paid to Eaton Vance for

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investment advisory services will be higher than if the Trust did not use leverage because the fees paid will be calculated on the basis of the Trust’s gross assets, including the proceeds from the issuance of preferred shares and any borrowings. As discussed under “Description of Capital Structure,” the Trust’s issuance of preferred shares may alter the voting power of Common Shareholders.

Capital raised through leverage will be subject to distribution and/or interest payments, which may exceed the income and appreciation on the assets purchased. The issuance of preferred shares involves offering expenses and other costs and may limit the Trust’s freedom to pay distributions on Common Shares or to engage in other activities. The issuance of a class of preferred shares having priority over the Common Shares creates an opportunity for greater return per Common Share, but at the same time such leveraging is a speculative technique that will increase the Trust’s exposure to capital risk. Unless the income and appreciation, if any, on assets acquired with offering proceeds exceed the cost of issuing additional classes of securities (and other Trust expenses), the use of leverage will diminish the investment performance of the Common Shares compared with what it would have been without leverage.

The Trust is subject to certain restrictions on investments imposed by guidelines of one or more Rating Agencies that issued ratings for preferred shares issued by the Trust. These guidelines impose asset coverage or Trust composition requirements that are more stringent than those imposed on the Trust by the 1940 Act. These covenants or guidelines do not currently and are not expected to impede Eaton Vance in managing the Trust’s portfolio in accordance with its investment objective and policies and it is not anticipated that they will so impede Eaton Vance in the future.

Under the 1940 Act, the Trust is not permitted to issue preferred shares unless immediately after such issuance the total asset value of the Trust’s portfolio is at least 200% of the liquidation value of the outstanding preferred shares plus the amount of any senior security representing indebtedness (i.e., such liquidation value and amount of indebtedness may not exceed 50% of the Trust’s total assets). In addition, the Trust is not permitted to declare any cash distribution on its Common Shares unless, at the time of such declaration, the NAV of the Trust’s portfolio (determined after deducting the amount of such distribution) is at least 200% of such liquidation value plus amount of indebtedness. The Trust intends, to the extent possible, to purchase or redeem preferred shares, from time to time, to maintain coverage of any preferred shares of at least 200%. As of September 30, 2018, the then outstanding APS and the outstanding borrowings represented 32.4% leverage, and there was an asset coverage of the APS of 284%. Holders of preferred shares, voting as a class, shall be entitled to elect two of the Trust’s Trustees. The holders of both the Common Shares and the preferred shares (voting together as a single class with each share entitling its holder to one vote) shall be entitled to elect the remaining Trustees of the Trust. In the event the Trust fails to pay distributions on its preferred shares for two years, preferred shareholders would be entitled to elect a majority of the Trustees until the preferred distributions in arrears are paid.

Under the 1940 Act, the Trust is not permitted to incur indebtedness, including through the issuance of debt securities, unless immediately thereafter the total asset value of the Trust’s portfolio is at least 300% of the liquidation value of the outstanding indebtedness (i.e., such liquidation value may not exceed 33 1/3% of the Trust’s total assets). In addition, the Trust is not permitted to declare any cash distribution on its Common Shares unless, at the time of such declaration, the NAV of the Trust’s portfolio (determined after deducting the amount of such distribution) is at least 300% of such liquidation value. If the Trust borrows money or enters into a commercial paper program, the Trust intends, to the extent possible, to retire outstanding debt, from time to time, to maintain coverage of any outstanding indebtedness of at least 300%. As of September 30, 2018, there were $113 million in outstanding borrowings.

To qualify for federal income taxation as a “regulated investment company,” the Trust must distribute in each taxable year at least 90% of its net investment income (including net interest income and net short-term gain). The Trust also will be required to distribute annually substantially all of its income and capital gain, if any, to avoid imposition of a nondeductible 4% federal excise tax. If the Trust is precluded from making distributions on the Common Shares because of any applicable asset coverage requirements, the terms of the preferred shares may provide that any amounts so precluded from being distributed, but required to be distributed for the Trust to meet the distribution requirements for qualification as a regulated investment company, will be paid to the holders of the preferred shares as a special distribution. This distribution can be expected to decrease the amount that holders of preferred shares would be entitled to receive upon redemption or liquidation of the shares.

Successful use of a leveraging strategy may depend on the Adviser’s ability to predict correctly interest rates and market movements, and there is no assurance that a leveraging strategy will be successful during any period in which it is employed.

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The following table is designed to illustrate the effect on the return to a holder of the Common Shares of leverage in the amount of approximately 35.4% of the Trust’s gross assets, assuming hypothetical annual returns of the Trust’s portfolio of minus 10% to plus 10%. As the table shows, leverage generally increases the return to Common Shareholders when portfolio return is positive and greater than the cost of leverage and decreases the return when the portfolio return is negative or less than the cost of leverage. The figures appearing in the table are hypothetical and actual returns may be greater or less than those appearing in the table.

Assumed portfolio return (net of expenses)		(10)%	(5)%	0%	5%	10%
Corresponding Common Share Total Return		(16.73)%	(8.99)%	(1.26)%	6.48%	14.21%

Assuming the utilization of leverage in the amount of 35.4% of the Trust’s gross assets, the cost of leverage is 2.30%. The additional income that the Trust must earn (net of expenses) in order to cover such costs is approximately 0.81% of net assets. The Trust’s actual costs of leverage will be based on market rates at the time the Trust undertakes a leveraging strategy, and such actual costs of leverage may be higher or lower than that assumed in the previous example.

ADDITIONAL RISK CONSIDERATIONS

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Derivatives Risk. The Trust’s exposure to derivatives involves risks different from, or possibly greater than, the risks associated with investing directly in securities and other investments. The use of derivatives can lead to losses because of adverse movements in the price or value of the asset, index, rate or instrument underlying a derivative, due to failure of a counterparty or due to tax or regulatory constraints. Derivatives may create leverage in the Trust, which represents a non-cash exposure to the underlying asset, index, rate or instrument. Leverage can increase both the risk and return potential of the Trust. Derivatives risk may be more significant when derivatives are used to enhance return or as a substitute for a cash investment position, rather than solely to hedge the risk of a position held by the Trust. Use of derivatives involves the exercise of specialized skill and judgment, and a transaction may be unsuccessful in whole or in part because of market behavior or unexpected events. Changes in the value of a derivative (including one used for hedging) may not correlate perfectly with the underlying asset, rate, index or instrument. Derivative instruments traded in over-the-counter markets may be difficult to value, may be illiquid, and may be subject to wide swings in valuation caused by changes in the value of the underlying instrument. If a derivative’s counterparty is unable to honor its commitments, the value of Trust shares may decline and the Trust could experience delays in the return of collateral or other assets held by the counterparty. The loss on derivative transactions may substantially exceed the initial investment, particularly when there is no stated limit on the Trust’s use of derivatives. A derivative investment also involves the risks relating to the asset, index, rate or instrument underlying the investment.

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Reinvestment Risk. Income from the Trust’s portfolio will decline if and when the Trust invests the proceeds from matured, traded or called debt obligations into lower yielding instruments.

Management Risk. The Trust is subject to management risk because it is actively managed. Eaton Vance and the individual portfolio managers invest the assets of the Trust as they deem appropriate in implementing the Trust’s investment strategy. Accordingly, the success of the Trust depends upon the investment skills and analytical abilities of Eaton Vance and the individual portfolio managers to develop and effectively implement strategies that achieve the Trust’s investment objective. There is no assurance that Eaton Vance and the individual portfolio managers will be successful in developing and implementing the Trust’s investment strategy. Subjective decisions made by Eaton Vance and the individual portfolio managers may cause the Trust to incur losses or to miss profit opportunities.

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Management of the Trust

BOARD OF TRUSTEES

The management of the Trust, including general supervision of the duties performed by the Adviser under the Advisory Agreement (as defined below), is the responsibility of the Trust’s Board under the laws of The Commonwealth of Massachusetts and the 1940 Act.

THE ADVISER

Eaton Vance acts as the Trust's investment adviser under an Investment Advisory Agreement (the “Advisory Agreement”). The Adviser's principal office is located at Two International Place, Boston, MA 02110. Eaton Vance, its affiliates and predecessor companies have been managing assets of individuals and institutions since 1924 and of investment companies since 1931. As of September 30, 2018, Eaton Vance and its affiliates managed approximately $459.8 billion of fund and separate account assets on behalf of clients, including approximately $43.9 billion in floating-rate income assets. Eaton Vance is a wholly-owned subsidiary of Eaton Vance Corp., a publicly-held holding company, which through its subsidiaries and affiliates engages primarily in investment management, administration and marketing activities.

Under the general supervision of the Trust’s Board, the Adviser will carry out the investment and reinvestment of the assets of the Trust, will furnish continuously an investment program with respect to the Trust, will determine which securities should be purchased, sold or exchanged, and will implement such determinations. The Adviser will furnish to the Trust investment advice and office facilities, equipment and personnel for servicing the investments of the Trust. The Adviser will compensate all Trustees and officers of the Trust who are members of the Adviser’s organization and who render investment services to the Trust, and will also compensate all other Adviser personnel who provide research and investment services to the Trust. In return for these services, facilities and payments, the Trust has agreed to pay the Adviser as compensation under the Advisory Agreement a fee in the amount of 0.76% (0.77% prior to May 1, 2018) of the average weekly gross assets of the Trust. Gross assets of the Trust shall be calculated by deducting accrued liabilities of the Trust not including the amount of any preferred shares outstanding or the principal amount of any indebtedness for money borrowed. During periods in which the Trust is using leverage, the fees paid to Eaton Vance for investment advisory services will be higher than if the Trust did not use leverage because the fees paid will be calculated on the basis of the Trust’s gross assets, including proceeds from any borrowings and from the issuance of preferred shares. The Trust is responsible for all expenses not expressly stated to be payable by another party (such as the expenses required to be paid pursuant to an agreement with the investment adviser or administrator).

Scott H. Page and John Redding comprise the investment team responsible for the overall and day-to-day management of the Trust’s investments. Mr. Page is a Vice President of Eaton Vance, is Co-Director of Eaton Vance’s Floating-Rate Loan Group and has been a portfolio manager of the Trust since October 1998. Mr. Redding is a Vice President of Eaton Vance and has been a portfolio manager of the Trust since November 2001.

Additional Information Regarding Portfolio Managers

The Statement of Additional Information provides additional information about the portfolio managers’ compensation, other accounts managed by the portfolio managers, and the portfolio managers’ ownership of securities in the Trust. The Statement of Additional Information is available free of charge by calling 1-800-225-6265 or by visiting the Trust’s website at http://www.eatonvance.com. The information contained in, or that can be accessed through, the Trust’s website is not part of this Prospectus or the Statement of Additional Information.

The Trust and the Adviser have adopted Codes of Ethics relating to personal securities transactions. The Codes of Ethics permit Adviser personnel to invest in securities (including securities that may be purchased or held by the Trust) for their own accounts, subject to the provisions of the Codes of Ethics and certain employees are also subject to certain pre-clearance, reporting and other restrictions and procedures contained in such Codes of Ethics.

The Trust’s annual shareholder report contains information regarding the basis for the Trustees’ approval of the Trust’s Advisory Agreement.

Eaton Vance Senior Income Trust

Prospectus dated [____], 2018

THE ADMINISTRATOR

Eaton Vance serves as administrator of the Trust and receives an administration fee computed at an annual rate of 0.25% of the Trust’s average weekly gross assets. Under an Amended and Restated Administrative Services Agreement with the Trust (“Administration Agreement”), Eaton Vance is responsible for managing the business affairs of the Trust, subject to the supervision of the Trust’s Board. Eaton Vance will furnish to the Trust all office facilities, equipment and personnel for administering the affairs of the Trust. Eaton Vance’s administrative services include recordkeeping, preparation and filing of documents required to comply with federal and state securities laws, supervising the activities of the Trust’s custodian and transfer agent, providing assistance in connection with the Trustees’ and shareholders’ meetings, providing service in connection with any repurchase offers and other administrative services necessary to conduct the Trust’s business.

Plan of Distribution

The Trust from time to time may offer its Common Shares through or to certain broker-dealers, including [_______], that have entered into selected dealer agreements relating to at-the-market offerings.

Eaton Vance Senior Income Trust

Prospectus dated [____], 2018

Distributions

While there are any borrowings or preferred shares outstanding, the Trust may not be permitted to declare any cash dividend or other distribution on its Common Shares in certain circumstances. See “Description of Capital Structure.”

Federal Income Tax Matters

The Trust intends to qualify each year as a regulated investment company (a “RIC”) under the Internal Revenue Code of 1986, as amended (the “Code”). Accordingly, the Trust intends to satisfy certain requirements relating to sources of its income and diversification of its assets and to distribute substantially all of its net income (including net tax-exempt interest income) and net short-term capital gains (after reduction by net long-term capital losses and any available capital loss carryforwards) in accordance with the timing requirements imposed by the Code, so as to maintain its RIC status. If it qualifies for treatment as a RIC and satisfies the above-mentioned distribution requirements, the Trust will not be subject to federal income tax on income paid to its shareholders in the form of dividends or capital gains distributions.

To qualify as a RIC for income tax purposes, the Trust must derive at least 90% of its annual gross income from dividends, interest, payments with respect to securities loans, gains from the sale or other disposition of stock, securities or foreign currencies, or other income (including, but not limited to, gains from options, futures or forward contracts) derived with respect to its business of investing in stock, securities and currencies, and net income derived from an interest in a qualified publicly traded partnership. The Trust must also distribute to its shareholders at least the sum of 90% of its investment company taxable income (as that term is defined in the Code, but determined without regard to the deduction for dividends paid) and 90% of its net tax-exempt interest income for each taxable year.

Eaton Vance Senior Income Trust

Prospectus dated [____], 2018

In order to avoid incurring a nondeductible 4% U.S. federal excise tax obligation, the Code requires that the Trust distribute (or be deemed to have distributed) by December 31 of each calendar year an amount at least equal to the sum of (i) 98% of its ordinary income for such year, (ii) 98.2% of its capital gain net income, generally computed on the basis of the one-year period ending on October 31 of such year, after reduction by any available capital loss carryforwards and (iii) 100% of any ordinary income and capital gain net income from the prior year (as previously computed) that was not paid out during such year and on which the Trust paid no U.S. federal income tax.

If the Trust does not qualify as a RIC for any taxable year, the Trust’s taxable income will be subject to corporate income taxes, and all distributions from earnings and profits, including distributions of net capital gain (if any), will be taxable to the shareholder as ordinary income. Such distributions will be treated as qualified dividend income with respect to shareholders who are individuals and will be eligible for the dividends received deduction in the case of shareholders taxed as corporations, provided certain holding period requirements are met. In order to requalify for taxation as a RIC, the Trust may be required to recognize unrealized gains, pay substantial taxes and interest, and make substantial distributions.

The Trust intends to make monthly distributions of net investment income after payment of dividends on any outstanding preferred shares or interest on any outstanding borrowings.

The Trust may also distribute its net realized capital gains, if any, generally not more than once per year. Distributions of the Trust’s net capital gains that are properly reported (“capital gain dividends”), if any, are taxable to shareholders as long-term capital gains, regardless of the length of time shares have been held by shareholders. (Net capital gain is the excess (if any) of net long-term capital gain over net short-term capital loss.) Dividends paid to shareholders out of the Trust’s current and accumulated earnings and profits will, except in the case of capital gain dividends, be taxable as ordinary income. Distributions, if any, in excess of the Trust’s earnings and profits will first reduce the adjusted tax basis of a holder’s shares and, after that basis has been reduced to zero, will constitute capital gains to the shareholder. See below for a summary of the maximum tax rates applicable to capital gains (including capital gain dividends). Dividends paid by the Trust generally will not qualify for the reduced tax rates applicable to qualified dividend income received by individual shareholders or the dividends received deduction generally available to corporate shareholders.

Distributions will be treated in the manner described above regardless of whether such distributions are paid in cash or invested in additional shares of the Trust. Shareholders receiving any distribution from the Trust in the form of additional shares pursuant to a dividend reinvestment plan will be treated as receiving a taxable distribution in the amount they would have received if they had elected to receive the distribution in cash, unless the Trust issues new shares that are trading at or above net asset value, in which case, such shareholders will be treated as receiving a distribution in the amount equal to the fair market value of the shares received, determined as of the reinvestment date.

As described in “Distributions” above, the Trust may retain some or all of its net capital gain. If the Trust retains any net capital gain, it will be subject to tax at regular corporate rates on the amount retained and will report the retained amount as undistributed capital gains as part of its annual reporting to its shareholders who, if subject to U.S. federal income tax on long-term capital gains, (i) will be required to include in income for U.S. federal income tax purposes, as long-term capital gain, their share of such undistributed amount; (ii) will be entitled to credit their proportionate shares of the tax paid by the Trust on such undistributed amount against their U.S. federal income tax liabilities, if any; and (iii) will be entitled to claim refunds to the extent the credit exceeds such liabilities. For U.S. federal income tax purposes, the tax basis of Common Shares owned by a Common Shareholder will be increased by an amount equal to the difference between the amount of undistributed capital gains included in the shareholder’s gross income and the tax deemed paid by the Common Shareholder under clause (ii) of the preceding sentence.

The Internal Revenue Service currently requires that a RIC that has two or more classes of stock allocate to each such class proportionate amounts of each type of its income (such as ordinary income and capital gains) based on the percentage of total dividends paid to each class for the tax year. Accordingly, if the Trust issues preferred shares, such as VRTP Shares, it will designate dividends made with respect to Common Shares and preferred shares as consisting of particular types of income (e.g., net capital gain and ordinary income) in accordance with the proportionate share of each class in the total dividends paid by the Trust during the year.

Eaton Vance Senior Income Trust

Prospectus dated [____], 2018

Gains or losses attributable to fluctuations in exchange rates between the time the Trust accrues income or receivables or expenses or other liabilities denominated in a foreign currency and the time the Trust actually collects such income or receivables or pays such liabilities are generally treated as ordinary income or loss. Transactions in foreign currencies, foreign currency-denominated debt securities and certain foreign currency options, futures contracts, forward contracts and similar instruments (to the extent permitted) may give rise to ordinary income or loss to the extent such income or loss results from fluctuations in the value of the foreign currency concerned.

The Trust will inform shareholders of the source and tax status of all distributions promptly after the close of each calendar year.

Selling shareholders will generally recognize capital gain or loss in an amount equal to the difference between the shareholder’s adjusted tax basis in the shares sold and the amount received.

The maximum tax rate applicable to capital gains recognized by individuals and other non-corporate taxpayers is (i) the same as the maximum ordinary income tax rate for gains recognized on the sale of capital assets held for one year or less, or (ii) 20% for gains recognized on the sale of capital assets held for more than one year (as well as capital gain dividends). Any loss on a disposition of shares held for six months or less will be treated as a long-term capital loss to the extent of any capital gain dividends received (or amounts designated as undistributed capital gains) with respect to those shares. For purposes of determining whether shares have been held for six months or less, the holding period is suspended for any periods during which the shareholder’s risk of loss is diminished as a result of holding one or more other positions in substantially similar or related property, or through certain options. Any loss realized on a sale or exchange of shares will be disallowed to the extent those shares are replaced by other substantially identical shares within a period of 61 days beginning 30 days before and ending 30 days after the date of disposition of the shares (whether through the reinvestment of distributions, which could occur, for example, if the shareholder is a participant in the Plan or otherwise). In that event, the basis of the replacement shares will be adjusted to reflect the disallowed loss.

An investor should be aware that, if shares are purchased shortly before the record date for any taxable dividend (including a capital gain dividend), the purchase price likely will reflect the value of the dividend and the investor then would receive a taxable distribution likely to reduce the trading value of such shares, in effect resulting in a taxable return of some of the purchase price. Taxable distributions to individuals and certain other non-corporate shareholders who have not provided their correct taxpayer identification number and other required certifications, may be subject to “backup” federal income tax withholding at the fourth lowest rate of tax applicable to a single individual (currently 28%).

An investor should also be aware that the benefits of the reduced tax rate applicable to long-term capital gains may be impacted by the application of the alternative minimum tax to individual shareholders.

Certain foreign entities including foreign entities acting as intermediaries may be subject to a 30% withholding tax on dividend income paid and, after December 31, 2018, on gross redemption proceeds paid under the Foreign Account Tax Compliance Act (“FATCA”). To avoid withholding, foreign financial institutions subject to FATCA must agree to disclose to the relevant revenue authorities certain information regarding their direct and indirect U.S. owners and other foreign entities must certify certain information regarding their direct and indirect U.S. owners to the Trust. For more detailed information regarding FATCA withholding and compliance, please refer to the Statement of Additional Information.

The foregoing briefly summarizes some of the important federal income tax consequences to shareholders of investing in shares, reflects the federal tax law as of the date of this prospectus, and does not address special tax rules applicable to certain types of investors, such as corporate and foreign investors. A more complete discussion of the tax rules applicable to the Trust and the shareholders can be found in the Statement of Additional Information that is incorporated by reference into this prospectus. Unless otherwise noted, this discussion assumes that an investor is a United States person and holds shares as a capital asset. This discussion is based upon current provisions of the Code, the regulations promulgated thereunder, and judicial and administrative ruling authorities, all of which are subject to change or differing interpretations by the courts or the Internal Revenue Service retroactively or prospectively. Investors should consult their tax advisors regarding other federal, state or local tax considerations that may be applicable in their particular circumstances, as well as any proposed tax law changes.

Eaton Vance Senior Income Trust

Prospectus dated [____], 2018

Dividend Reinvestment Plan

The Trust offers a dividend reinvestment plan (the “Plan”) pursuant to which Common Shareholders automatically have distributions reinvestment in Common Shares of the Trust unless they elect otherwise through their investment dealer. Common Shareholders who elect not to participate in the Plan will receive all Trust distributions in cash paid by check mailed directly to the Common Shareholder of record (or, if the Common Shares are held in street or other nominee name, then to the nominee) by American Stock Transfer & Trust Company, LLC (“AST” or the “Plan Agent”), as disbursing agent. On the distribution payment date, if the net asset value per Common Share is equal to or less than the market price per Common Share plus estimated brokerage commissions, then new Common Shares will be issued. The number of Common Shares shall be determined by the greater of the net asset value per Common Share or 95% of the market price. Otherwise, Common Shares generally will be purchased on the open market by the Plan Agent. Distributions subject to income tax (if any) are taxable whether or not shares are reinvested.

If your shares are in the name of a brokerage firm, bank, or other nominee, you can ask the firm or nominee to participate in the Plan on your behalf. If the nominee does not offer the Plan, you will need to request that your shares be re-registered in your name with the Trust’s transfer agent, AST, or you will not be able to participate.

The Plan Agent’s service fee for handling distributions will be paid by the Trust. Each participant will be charged their pro rata share of brokerage commissions on all open-market purchases.

Plan participants may withdraw from the Plan at any time by writing to the Plan Agent at the address noted on page 47. If you withdraw, you will receive shares in your name for all Common Shares credited to your account under the Plan. If a participant elects by written notice to the Plan Agent to have the Plan Agent sell part or all of his or her Common Shares and remit the proceeds, the Plan Agent is authorized to deduct a $5.00 fee plus brokerage commissions from the proceeds.

Any inquiries regarding the Plan can be directed to the Plan Agent, AST, at 1-866-439-6787.

Description of Capital Structure

The Trust is an unincorporated business trust established under the laws of The Commonwealth of Massachusetts by an Agreement and Declaration of Trust (the “Declaration of Trust”). The Declaration of Trust provides that the Trustees of the Trust may authorize separate classes of shares of beneficial interest. The Trustees have authorized an unlimited number of Common Shares. The Trust intends to hold annual meetings of shareholders in compliance with the requirements of the NYSE.

COMMON SHARES

The Declaration of Trust permits the Trust to issue an unlimited number of full and fractional Common Shares. Each Common Share represents an equal proportionate interest in the assets of the Trust with each other Common Share in the Trust. Holders of Common Shares will be entitled to the payment of dividends when, as and if declared by the Board. The 1940 Act or the terms of any borrowings or preferred shares may limit the payment of dividends to the holders of Common Shares. Each whole Common Share shall be entitled to one vote as to matters on which it is entitled to vote pursuant to the terms of the Declaration of Trust on file with the SEC. Upon liquidation of the Trust, after paying or adequately providing for the payment of all liabilities of the Trust and the liquidation preference with respect to any outstanding preferred shares, and upon receipt of such releases, indemnities and refunding agreements as they deem necessary for their protection, the Trustees may distribute the remaining assets of the Trust among the holders of the Common Shares. The Declaration of Trust provides that shareholders are not liable for any liabilities of the Trust and permits inclusion of a clause to that effect in every agreement entered into by the Trust and in coordination with the Trust's By-Laws indemnifies shareholders against any such liability. Although shareholders of an unincorporated business trust established under Massachusetts law, in certain limited circumstances, may be held personally liable for the obligations of the Trust as though they were general partners, the provisions of the Declaration of Trust and By-Laws described in the foregoing sentence make the likelihood of such personal liability remote.

While there are any borrowings or preferred shares outstanding, the Trust may not be permitted to declare any cash dividend or other distribution on its Common Shares, unless at the time of such declaration, (i) all accrued dividends on preferred shares or accrued interest on borrowings have been paid and (ii) the value of the Trust's total assets (determined after deducting the amount of such dividend or other distribution), less all liabilities and indebtedness of the Trust not represented by senior securities, is at least 300% of the aggregate amount of such securities representing indebtedness and at least 200% of the aggregate amount of securities representing indebtedness plus the aggregate liquidation value of the outstanding preferred shares (expected to equal the aggregate original purchase price of the outstanding preferred shares plus redemption premium, if any, together with any accrued and unpaid dividends thereon, whether or not earned or declared and on a cumulative basis). In addition to the requirements of the 1940 Act, the Trust may be required to comply with other asset coverage requirements as a condition of the Trust obtaining a rating of the

Eaton Vance Senior Income Trust

Prospectus dated [____], 2018

preferred shares from a Rating Agency. These requirements may include an asset coverage test more stringent than under the 1940 Act. This limitation on the Trust's ability to make distributions on its Common Shares could in certain circumstances impair the ability of the Trust to maintain its qualification for taxation as a regulated investment company for federal income tax purposes. The Trust intends, however, to the extent possible to purchase or redeem preferred shares or reduce borrowings from time to time to maintain compliance with such asset coverage requirements and may pay special dividends to the holders of the preferred shares in certain circumstances in connection with any such impairment of the Trust's status as a regulated investment company. See “Investment Objective, Policies and Risks,” “Distributions” and “Federal Income Tax Matters.” Depending on the timing of any such redemption or repayment, the Trust may be required to pay a premium in addition to the liquidation preference of the preferred shares to the holders thereof.

The Trust has no present intention of offering additional Common Shares, except as described herein. Other offerings of its Common Shares, if made, will require approval of the Board. Any additional offering will not be sold at a price per Common Share below the then current NAV (exclusive of underwriting discounts and commissions) except in connection with an offering to existing shareholders or with the consent of a majority of the Trust's outstanding Common Shares. The Common Shares have no preemptive rights.

The Trust generally will not issue Common Share certificates. However, upon written request to the Trust's transfer agent, a share certificate will be issued for any or all of the full Common Shares credited to an investor's account. Common Share certificates that have been issued to an investor may be returned at any time.

CREDIT FACILITY

The Trust currently leverages through borrowings, and has entered into an Agreement with conduit lenders and a bank to allow it to borrow up to $125 million ($100 million prior to September 13, 2018). The proceeds of which were used to invest in accordance with the Trust’s investment practices and to partially redeem the Trust’s APS. Borrowings under the Agreement are secured by the assets of the Trust. Interest is charged at a rate above the conduits’ commercial paper issuance rate and is payable monthly. Under the terms of the Agreement, the Trust also pays a program fee of 0.67% per annum on its outstanding borrowings to administer the facility and a liquidity fee of 0.15% (0.25% if the outstanding loan amount is less than or equal to 60% of the total facility size) per annum on the borrowing limit under the Agreement. Program and liquidity fees for the year ended June 30, 2018 totaled $739,164 and for the three months ended September 30, 2018 totaled $197,384. In connection with the increase in the borrowing limit on September 13, 2018, the Trust paid an additional upfront fee of $12,260 which is being amortized over the remaining term of the Agreement to March 11, 2019. In connection with the renewal of the Agreement in March 2018, the Trust paid an upfront fee of $100,000 that is being amortized to interest expense over a period of one year through March 2019. The Trust is required to maintain certain net asset levels during the term of the Agreement. As of September 30, 2018, the Trust had borrowings outstanding under the Agreement of $113 million at an interest rate of 2.21%, in addition to outstanding APS. Based on the short-term nature of the borrowings under the Agreement and the variable interest rate, the carrying amount of the borrowings at June 30, 2018 approximated its fair value. For the year ended June 30, 2018, the average borrowings under the Agreement and the average interest rate (excluding fees) were $87,202,740 and 1.63%, respectively. For the three months ended September 30, 2018, the average borrowings under the Agreement and the average interest rate (excluding fees) were $92,891,304 and 2.16%, respectively.

In addition, the credit facility/program contains covenants that, among other things, limit the Trust's ability to pay dividends in certain circumstances, incur additional debt, change its fundamental investment policies and engage in certain transactions, including mergers and consolidations, and may require asset coverage ratios in addition to those required by the 1940 Act. The Trust is required to pledge its assets and to maintain a portion of its assets in cash or high-grade securities as a reserve against interest or principal payments and expenses. The credit facility/program contains customary covenant, negative covenant and default provisions. In addition, any such credit facility/program entered into in the future may be replaced or refinanced by one or more credit facilities having substantially different terms or by the issuance of preferred shares or debt securities.

REPURCHASE OF COMMON SHARES AND OTHER DISCOUNT MEASURES

Because shares of closed-end management investment companies frequently trade at a discount to their NAVs, the Board has determined that from time to time it may be in the interest of shareholders for the Trust to take corrective actions. The Board, in consultation with Eaton Vance, will review at least annually the possibility of open market repurchases and/or tender offers for the Common Shares and will consider such factors as the market price of the Common Shares, the NAV of the Common Shares, the liquidity of the assets of the Trust, effect on the Trust's expenses, whether such transactions would impair the Trust's status as a regulated investment company or result in a failure to comply with applicable asset coverage requirements, general economic conditions and such other events or conditions which may have a material effect on the Trust's ability to consummate such transactions. There are no assurances that the Board will, in fact, decide to undertake either of these actions or if undertaken, that such actions will result in the Trust's Common Shares trading at a price which is equal to or approximates their NAV. In recognition of the possibility that the Common Shares might trade at a discount to NAV and that any such discount may not be in the interest of shareholders, the Board, in consultation with Eaton Vance, from time to time may review possible actions to reduce any such discount.

Eaton Vance Senior Income Trust

Prospectus dated [____], 2018

PREFERRED SHARES

The Declaration of Trust authorizes the issuance of an unlimited number of shares of beneficial interest with preference rights, including preferred shares, having a par value of $0.01 per share, in one or more series, with rights as determined by the Board, by action of the Board without the approval of the Common Shareholders On June 27, 2001, the Trust issued 2,200 Series A APS and 2,200 Series B APS, with a liquidation preference per share of $25,000 plus accumulated but unpaid dividends. On September 23, 2016, the Trust repurchased 968 Series A APS and 968 Series B APS. On September 14, 2018, the Trust repurchased 480 Series A APS and 480 Series B APS. The APS have seniority over the Common Shares.

Under the requirements of the 1940 Act, the Trust must, immediately after the issuance of any preferred shares, have an “asset coverage” of at least 200%. Asset coverage means the ratio which the value of the total assets of the Trust, less all liability and indebtedness not represented by senior securities (as defined in the 1940 Act), bears to the aggregate amount of senior securities representing indebtedness of the Trust, if any, plus the aggregate liquidation preference of the preferred shares. The liquidation value of the preferred shares is expected to equal to their aggregate original purchase price plus the applicable redemption premium, if any, together with any accrued and unpaid distributions thereon (on a cumulative basis), whether or not earned or declared. The terms of the preferred shares, including their distribution rate, voting rights, liquidation preference and redemption provisions, are determined by the Board (subject to applicable law and the Trust’s Declaration of Trust). The Trust may issue preferred shares that provide for the periodic redetermination of the distribution rate at relatively short intervals through an auction or remarketing procedure, although the terms of the preferred shares may also enable the Trust to lengthen such intervals. At times, the distribution rate on the Trust’s preferred shares may exceed the Trust’s return after expenses on the investment of proceeds from the preferred shares and the Trust’s leverage structure, resulting in a lower rate of return to Common Shareholders than if the preferred shares were not outstanding.

In the event of any voluntary or involuntary liquidation, dissolution or winding up of the Trust, the terms of any preferred shares may entitle the holders of preferred shares to receive a preferential liquidating distribution (expected to equal to the original purchase price per share plus the applicable redemption premium, if any, together with accrued and unpaid distributions, whether or not earned or declared and on a cumulative basis) before any distribution of assets is made to holders of Common Shares. After payment of the full amount of the liquidating distribution to which they are entitled, the preferred shareholders would not be entitled to any further participation in any distribution of assets by the Trust.

Holders of preferred shares, voting as a class, shall be entitled to elect two of the Trust’s Trustees. The holders of both the Common Shares and the preferred shares (voting together as a single class with each share entitling its holder to one vote) shall be entitled to elect the remaining Trustees of the Trust. Under the 1940 Act, if at any time distributions on the preferred shares are unpaid in an amount equal to two full years’ distributions thereon, the holders of all outstanding preferred shares, voting as a class, will be allowed to elect a majority of the Trust’s Trustees until all distributions in arrears have been paid or declared and set apart for payment. In addition, if required by a Rating Agency rating the preferred shares or if the Board determines it to be in the best interests of the Common Shareholders, issuance of the preferred shares may result in more restrictive provisions than required by the 1940 Act being imposed. In this regard, holders of the preferred shares may be entitled to elect a majority of the Trust’s Board in other circumstances, for example, if one payment on the preferred shares is in arrears. The differing rights of the holders of preferred and Common Shares with respect to the election of Trustees do not affect the obligation of all Trustees to take actions they believe to be consistent with the best interests of the Trust. All such actions must be consistent with (i) the obligations of the Trust with respect to the holders of preferred shares (which obligations arise primarily from the contractual terms of the preferred shares, as specified in the Declaration of Trust and By-laws of the Trust) and (ii) the fiduciary duties owed to the Trust, which include the duties of loyalty and care.

Eaton Vance Senior Income Trust

Prospectus dated [____], 2018

CERTAIN PROVISIONS OF THE DECLARATION OF TRUST

Anti-Takeover Provisions in the Declaration of Trust

The Declaration of Trust includes provisions that could have the effect of limiting the ability of other entities or persons to acquire control of the Trust or to change the composition of its Board, and could have the effect of depriving holders of Common Shares of an opportunity to sell their shares at a premium over prevailing market prices by discouraging a third party from seeking to obtain control of the Trust. These provisions may have the effect of discouraging attempts to acquire control of the Trust, which attempts could have the effect of increasing the expenses of the Trust and interfering with the normal operation of the Trust. The Board is divided into three classes, with the term of one class expiring at each annual meeting of holders of Common Shares and preferred shares. At each annual meeting, one class of Trustees is elected to a three-year term. This provision could delay for up to two years the replacement of a majority of the Board. A Trustee may be removed from office only for cause by a written instrument signed by the remaining Trustees or by a vote of the holders of at least two-thirds of the class of shares of the Trust that elected such Trustee and are entitled to vote on the matter.

In addition, the Declaration of Trust requires the favorable vote of the holders of at least 75% of the outstanding shares of each class of the Trust, voting as a class, then entitled to vote to approve, adopt or authorize certain transactions with 5%-or-greater holders (“Principal Shareholders”) of a class of shares and their associates, unless the Board shall by resolution have approved a memorandum of understanding with such holders, in which case normal voting requirements would be in effect. For purposes of these provisions, a Principal Shareholder refers to any person who, whether directly or indirectly and whether alone or together with its affiliates and associates, beneficially owns 5% or more of the outstanding shares of any class of beneficial interest of the Trust. The transactions subject to these special approval requirements are: (i) the merger or consolidation of the Trust or any subsidiary of the Trust with or into any Principal Shareholder; (ii) the issuance of any securities of the Trust to any Principal Shareholder for cash; (iii) the sale, lease or exchange of all or any substantial part of the assets of the Trust to any Principal Shareholder (except assets having an aggregate fair market value of less than $1,000,000, aggregating for the purpose of such computation all assets sold, leased or exchanged in any series of similar transactions within a twelve-month period); or (iv) the sale, lease or exchange to the Trust or any subsidiary thereof, in exchange for securities of the Trust, of any assets of any Principal Shareholder (except assets having an aggregate fair market value of less than $1,000,000, aggregating for the purposes of such computation all assets sold, leased or exchanged in any series of similar transactions within a twelve-month period).

The Board has determined that provisions with respect to the Board and the 75% voting requirements described above, which voting requirements are greater than the minimum requirements under Massachusetts law or the 1940 Act, are in the best interest of holders of Common Shares and preferred shares generally. Reference should be made to the Declaration of Trust on file with the SEC for the full text of these provisions.

Conversion to Open-End Fund

The Trust may be converted to an open-end investment company at any time if approved by the lesser of (i) two-thirds or more of the Trust’s then outstanding Common Shares and preferred shares, each voting separately as a class, or (ii) more than 50% of the then outstanding Common Shares and preferred shares, voting separately as a class if such conversion is recommended by at least 75% of the Trustees then in office. If approved in the foregoing manner, conversion of the Trust could not occur until 90 days after the Common Shareholders’ meeting at which such conversion was approved and would also require at least 30 days’ prior notice to all Common Shareholders. Conversion of the Trust to an open-end management investment company also would require the redemption of any outstanding preferred shares, including APS, and could require the repayment of borrowings. The Board believes that the closed-end structure is desirable, given the Trust’s investment objective and policies. Investors should assume, therefore, that it is unlikely that the Board would vote to convert the Trust to an open-end management investment company.

Custodian and Transfer Agent

State Street Bank and Trust Company (“State Street”), State Street Financial Center, One Lincoln Street, Boston, MA 02111, is the custodian of the Trust and will maintain custody of the securities and cash of the Trust. State Street maintains the Trust’s general ledger and computes NAV per share at least weekly. State Street also attends to details in connection with the sale, exchange, substitution, transfer and other dealings with the Trust’s investments, and receives and disburses all funds. State Street also assists in preparation of shareholder reports and the electronic filing of such reports with the SEC.

American Stock Transfer & Trust Company, LLC, 6201 15th Avenue, Brooklyn, NY 11219 is the transfer agent and dividend disbursing agent of the Trust.

Eaton Vance Senior Income Trust

Prospectus dated [____], 2018

Legal Opinions

Certain legal matters in connection with the Common Shares will be passed upon for the Trust by internal counsel for Eaton Vance.

Reports to Shareholders

The Trust will send to Common Shareholders unaudited semi-annual and audited annual reports, including a list of investments held.

Independent Registered Public Accounting Firm

[________________], independent registered public accounting firm, audits the Trust’s financial statements and provides other audit, tax and related services.

Additional Information

The Prospectus and the Statement of Additional Information do not contain all of the information set forth in the Registration Statement that the Trust has filed with the SEC. The complete Registration Statement may be obtained from the SEC upon payment of the fee prescribed by its rules and regulations. The Statement of Additional Information can be obtained without charge by calling 1-800-262-1122.

Statements contained in this Prospectus as to the contents of any contract or other document referred to are not necessarily complete, and, in each instance, reference is made to the copy of such contract or other document filed as an exhibit to the Registration Statement of which this Prospectus forms a part, each such statement being qualified in all respects by such reference.

Eaton Vance Senior Income Trust

Prospectus dated [____], 2018

Table of Contents for the Statement of Additional Information

	Page
Additional Investment Information and Restrictions	2
Trustees and Officers	16
Investment Advisory and Other Services	24
Determination of Net Asset Value	28
Portfolio Trading	29
Taxes	31
Other Information	35
Custodian	35
Independent Registered Public Accounting Firm	35
Financial Statements	35
APPENDIX A: Ratings	36
APPENDIX B: Proxy Voting Policy and Procedures	45

Eaton Vance Senior Income Trust

Prospectus dated [____], 2018

The Trust’s Privacy Policy

The Eaton Vance organization is committed to ensuring your financial privacy. Each of the financial institutions identified below has in effect the following policy (“Privacy Policy”) with respect to nonpublic personal information about its customers:

Only such information received from you, through application forms or otherwise, and information about your Eaton Vance fund transactions will be collected. This may include information such as name, address, social security number, tax status, account balances and transactions.

None of such information about you (or former customers) will be disclosed to anyone, except as permitted by law (which includes disclosure to employees necessary to service your account). In the normal course of servicing a customer’s account, Eaton Vance may share information with unaffiliated third parties that perform various required services such as transfer agents, custodians and broker/dealers.

Policies and procedures (including physical, electronic and procedural safeguards) are in place that are designed to protect the confidentiality of such information.

We reserve the right to change our Privacy Policy at any time upon proper notification to you. Customers may want to review our Privacy Policy periodically for changes by accessing the link on our homepage: www.eatonvance.com.

Our pledge of privacy applies to the following entities within the Eaton Vance organization: the Eaton Vance Family of Funds, Eaton Vance Management, Eaton Vance Investment Counsel, Eaton Vance Distributors, Inc., Eaton Vance Trust Company, Eaton Vance Management (International) Limited, Eaton Vance Advisers International Ltd., Eaton Vance Management’s Real Estate Investment Group and Boston Management and Research.

In addition, our Privacy Policy applies only to those Eaton Vance customers who are individuals and who have a direct relationship with us. If a customer’s account (i.e., fund shares) is held in the name of a third-party financial adviser/broker-dealer, it is likely that only such adviser’s privacy policies apply to the customer. This notice supersedes all previously issued privacy disclosures.

For more information about Eaton Vance’s Privacy Policy, please call 1-800-262-1122.

Eaton Vance Senior Income Trust

Prospectus dated [____], 2018

Up to [___________] Shares

Eaton Vance Senior Income Trust

Common Shares

Prospectus [_________], 2018

Printed on recycled paper.

Eaton Vance Senior Income Trust

Prospectus dated [____], 2018

SUBJECT TO COMPLETION

[______], 2018

STATEMENT OF
ADDITIONAL INFORMATION
[_________]

Eaton Vance Senior Income Trust

Two International Place
Boston, Massachusetts 02110
1-800-262-1122

Table of Contents

	Page
Additional Investment Information and Restrictions	2
Trustees and Officers	16
Investment Advisory and Other Services	24
Determination of Net Asset Value	28
Portfolio Trading	29
Taxes	31
Other Information	35
Custodian	35
Independent Registered Public Accounting Firm	35
Financial Statements	35
APPENDIX A: Ratings	36
APPENDIX B: Proxy Voting Policy and Procedures	45

THE INFORMATION IN THIS STATEMENT OF ADDITIONAL INFORMATION (“SAI”) IS NOT COMPLETE AND MAY BE CHANGED. THESE SECURITIES MAY NOT BE SOLD UNTIL THE REGISTRATION STATEMENT FILED WITH THE SECURITIES AND EXCHANGE COMMISSION IS EFFECTIVE. THIS SAI, WHICH IS NOT A PROSPECTUS, IS NOT AN OFFER TO SELL THESE SECURITIES AND IS NOT SOLICITING AN OFFER TO BUY THESE SECURITIES IN ANY STATE WHERE THE OFFER OR SALE IS NOT PERMITTED.

THIS STATEMENT OF ADDITIONAL INFORMATION (“SAI”) IS NOT A PROSPECTUS AND IS AUTHORIZED FOR DISTRIBUTION TO PROSPECTIVE INVESTORS ONLY IF PRECEDED OR ACCOMPANIED BY THE PROSPECTUS OF EATON VANCE SENIOR INCOME TRUST (THE “TRUST”) DATED [______], 2018, AS SUPPLEMENTED FROM TIME TO TIME, WHICH IS INCORPORATED HEREIN BY REFERENCE. THIS SAI SHOULD BE READ IN CONJUNCTION WITH SUCH PROSPECTUS, A COPY OF WHICH MAY BE OBTAINED WITHOUT CHARGE BY CONTACTING YOUR FINANCIAL INTERMEDIARY OR CALLING THE TRUST AT 1-800-262-1122.

Capitalized terms used in this SAI and not otherwise defined have the meanings given them in the Trust’s Prospectus and any related Prospectus Supplements.

ADDITIONAL INVESTMENT INFORMATION AND RESTRICTIONS

Primary investment strategies are described in the Prospectus. The following is a description of the various investment practices that may be engaged in, whether as a primary or secondary strategy, and a summary of certain attendant risks. The Adviser may not buy any of the following instruments or use any of the following techniques unless it believes that doing so will help to achieve the Trust’s investment objective.

SENIOR LOANS

Structure of Senior Loans. A Senior Loan is typically originated, negotiated and structured by a U.S. or foreign commercial bank, insurance company, finance company or other financial institution (the “Agent”) for a group of loan investors (“Loan Investors”). The Agent typically administers and enforces the Senior Loan on behalf of the other Loan Investors in the syndicate. In addition, an institution, typically but not always the Agent, holds any collateral on behalf of the Loan Investors.

Senior Loans primarily include senior floating-rate loans to corporations and secondarily institutionally traded senior floating-rate debt obligations issued by an asset-backed pool, and interests therein. Loan interests primarily take the form of assignments purchased in the primary or secondary market. Loan interests may also take the form of participation interests in a Senior Loan. Such loan interests may be acquired from U.S. or foreign commercial banks, insurance companies, finance companies or other financial institutions who have made loans or are Loan Investors or from other investors in loan interests.

The Trust typically purchases “Assignments” from the Agent or other Loan Investors. The purchaser of an Assignment typically succeeds to all the rights and obligations under the Loan Agreement of the assigning Loan Investor and becomes a Loan Investor under the Loan Agreement with the same rights and obligations as the assigning Loan Investor. Assignments may, however, be arranged through private negotiations between potential assignees and potential assignors, and the rights and obligations acquired by the purchaser of an Assignment may differ from, and be more limited than, those held by the assigning Loan Investor.

The Trust also may invest in “Participations.” Participations by the Trust in a Loan Investor’s portion of a Senior Loan typically will result in the Trust having a contractual relationship only with such Loan Investor, not with the Borrower. As a result, the Trust may have the right to receive payments of principal, interest and any fees to which it is entitled only from the Loan Investor selling the Participation and only upon receipt by such Loan Investor of such payments from the Borrower. In connection with purchasing Participations, the Trust generally will have no right to enforce compliance by the Borrower with the terms of the loan agreement, nor any rights with respect to any funds acquired by other Loan Investors through set-off against the Borrower and the Trust may not directly benefit from the collateral supporting the Senior Loan in which it has purchased the Participation. As a result, the Trust may assume the credit risk of both the Borrower and the Loan Investor selling the Participation. In the event of the insolvency of the Loan Investor selling a Participation, the Trust may be treated as a general creditor of such Loan Investor. The selling Loan Investors and other persons interpositioned between such Loan Investors and the Trust with respect to such Participations will likely conduct their principal business activities in the banking, finance and financial services industries. Persons engaged in such industries may be more susceptible to, among other things, fluctuations in interest rates, changes in the Federal Open Market Committee’s monetary policy, governmental regulations concerning such industries and concerning capital raising activities generally and fluctuations in the financial markets generally.

The Trust will only acquire Participations if the Loan Investor selling the Participation, and any other persons interpositioned between the Trust and the Loan Investor, at the time of investment has outstanding debt or deposit obligations rated investment grade (BBB or A-3 or higher by S&P Global Ratings (“S&P”) or Baa or P-3 or higher by Moody’s Investors Service, Inc. (“Moody’s”) or comparably rated by another nationally recognized rating agency) or determined by the Adviser to be of comparable quality. Securities rated Baa by Moody’s have speculative characteristics. Long-term debt rated BBB by S&P is regarded by S&P as having adequate capacity to pay interest and repay principal and debt rated Baa by Moody’s is regarded by Moody’s as a medium grade obligation, i.e., it is neither highly protected nor poorly secured. Commercial paper rated A-3 by S&P indicates that S&P believes such obligations exhibit adequate protection parameters but that adverse economic conditions or changing circumstances are more likely to lead to a weakened capacity of the obligor to meet its financial commitment on the obligation and issues of commercial paper rated P-3 by Moody’s are considered by Moody’s to have an acceptable ability for repayment of senior short-term obligations. The effect of industry characteristics and market compositions may be more pronounced. Indebtedness of companies whose creditworthiness is poor involves substantially greater risks, and may be highly speculative. Some companies may never pay off their indebtedness, or may pay only a small fraction of the amount owed. Consequently, when investing in indebtedness of companies with poor credit, the Trust bears a substantial risk of losing the entire amount invested.

Eaton Vance Senior Income Trust

SAI dated [_____], 2018

Loan Collateral. In order to borrow money pursuant to a Senior Loan, a Borrower will frequently, for the term of the Senior Loan, pledge collateral, including but not limited to, (i) working capital assets, such as accounts receivable and inventory; (ii) tangible fixed assets, such as real property, buildings and equipment; (iii) intangible assets, such as trademarks and patent rights (but excluding goodwill); and (iv) security interests in shares of stock of subsidiaries or affiliates. In the case of Senior Loans made to non-public companies, the company’s shareholders or owners may provide collateral in the form of secured guarantees and/or security interests in assets that they own. In many instances, a Senior Loan may be secured only by stock in the Borrower or its subsidiaries. Collateral may consist of assets that may not be readily liquidated, and there is no assurance that the liquidation of such assets would satisfy fully a Borrower’s obligations under a Senior Loan.

Certain Fees Paid to the Trust. In the process of buying, selling and holding Senior Loans, the Trust may receive and/or pay certain fees. These fees are in addition to interest payments received and may include facility fees, commitment fees, amendment fees, commissions and prepayment penalty fees. When the Trust buys a Senior Loan it may receive a facility fee and when it sells a Senior Loan it may pay a facility fee. On an ongoing basis, the Trust may receive a commitment fee based on the undrawn portion of the underlying line of credit portion of a Senior Loan. In certain circumstances, the Trust may receive a prepayment penalty fee upon the prepayment of a Senior Loan by a Borrower. Other fees received by the Trust may include covenant waiver fees and covenant modification fees.

Borrower Covenants. A Borrower must comply with various restrictive covenants contained in a loan agreement or note purchase agreement between the Borrower and the holders of the Senior Loan (the “Loan Agreement”). Such covenants, in addition to requiring the scheduled payment of interest and principal, may include restrictions on dividend payments and other distributions to stockholders, provisions requiring the Borrower to maintain specific minimum financial ratios, and limits on total debt. In addition, the Loan Agreement may contain a covenant requiring the Borrower to prepay the Senior Loan with any free cash flow. Free cash flow is generally defined as net cash flow after scheduled debt service payments and permitted capital expenditures, and includes the proceeds from asset dispositions or sales of securities. A breach of a covenant that is not waived by the Agent, or by the Loan Investors directly, as the case may be, is normally an event of acceleration; i.e., the Agent, or the Loan Investors directly, as the case may be, has the right to call the outstanding Senior Loan. U.S. federal securities laws afford certain protections against fraud and misrepresentation in connection with the offering or sale of a security, as well as against manipulation of trading markets for securities. The typical practice of a lender in relying exclusively or primarily on reports from the borrower may involve the risk of fraud, misrepresentation, or market manipulation by the borrower. It is unclear whether U.S. federal securities law protections are available to an investment in a loan. In certain circumstances, loans may not be deemed to be securities, and in the event of fraud or misrepresentation by a borrower, lenders may not have the protection of the anti-fraud provisions of the federal securities laws. However, contractual provisions in the loan documents may offer some protections, and lenders may also avail themselves of common-law fraud protections under applicable state law. In the case of a Senior Loan in the form of Participation, the agreement between the buyer and seller may limit the rights of the holder to vote on certain changes that may be made to the Loan Agreement, such as waiving a breach of a covenant. However, the holder of the Participation will, in almost all cases, have the right to vote on certain fundamental issues such as changes in principal amount, payment dates and interest rate.

Administration of Loans. In a typical Senior Loan, the Agent administers the terms of the Loan Agreement. In such cases, the Agent is normally responsible for the collection of principal and interest payments from the Borrower and the apportionment of these payments to the credit of all institutions that are parties to the Loan Agreement. The Trust will generally rely upon the Agent or an intermediate participant to receive and forward to the Trust its portion of the principal and interest payments on the Senior Loan. Furthermore, unless under the terms of a Participation Agreement the Trust has direct recourse against the Borrower, the Trust will rely on the Agent and the other Loan Investors to use appropriate credit remedies against the Borrower. The Agent is typically responsible for monitoring compliance with covenants contained in the Loan Agreement based upon reports prepared by the Borrower. The seller of the Senior Loan usually does, but is often not obligated to, notify holders of Senior Loans of any failures of compliance. The Agent may monitor the value of the collateral and, if the value of the collateral declines, may accelerate the Senior Loan, may give the Borrower an opportunity to provide additional collateral or may seek other protection for the benefit of the participants in the Senior Loan. The Agent is compensated by the Borrower for providing these services under a Loan Agreement, and such compensation may include special fees paid upon structuring and funding the Senior Loan and other fees paid on a continuing basis. With respect to Senior Loans for which the Agent does not perform such administrative and enforcement functions, the Trust will perform such tasks on its own behalf, although a collateral bank will typically hold any collateral on behalf of the Trust and the other Loan Investors pursuant to the applicable Loan Agreement.

Eaton Vance Senior Income Trust

SAI dated [_____], 2018

A financial institution’s appointment as Agent may usually be terminated in the event that it fails to observe the requisite standard of care or becomes insolvent, enters Federal Deposit Insurance Corporation (“FDIC”) receivership, or, if not FDIC insured, enters into bankruptcy proceedings. A successor Agent would generally be appointed to replace the terminated Agent, and assets held by the Agent under the Loan Agreement should remain available to holders of Senior Loans. However, if assets held by the Agent for the benefit of the Trust were determined to be subject to the claims of the Agent’s general creditors, the Trust might incur certain costs and delays in realizing payment on a Senior Loan, or suffer a loss of principal and/or interest. In situations involving intermediate participants, similar risks may arise.

Prepayments. Senior Loans will usually require, in addition to scheduled payments of interest and principal, the prepayment of the Senior Loan from a portion of free cash flow, as defined above. The degree to which Borrowers prepay Senior Loans, whether as a contractual requirement or at their election, may be affected by general business conditions, the financial condition of the Borrower and competitive conditions among Loan Investors, among other factors. As such, prepayments cannot be predicted with accuracy. Upon a prepayment, either in part or in full, the actual outstanding debt on which the Trust derives interest income will be reduced. However, the Trust may receive both a prepayment penalty fee from the prepaying Borrower and a facility fee upon the purchase of a new Senior Loan with the proceeds from the prepayment of the former. Prepayments generally will not materially affect the Trust’s performance because the Trust typically is able to reinvest prepayments in other Senior Loans that have similar yields and because receipt of such fees may mitigate any adverse impact on the Trust’s yield.

Other Information Regarding Senior Loans. From time to time the Adviser and its affiliates may borrow money from various banks in connection with their business activities. Such banks may also sell interests in Senior Loans to or acquire them from the Trust or may be intermediate participants with respect to Senior Loans in which the Trust owns interests. Such banks may also act as Agents for Senior Loans held by the Trust.

The Trust may acquire interests in Senior Loans that are designed to provide temporary or “bridge” financing to a Borrower pending the sale of identified assets or the arrangement of longer-term loans or the issuance and sale of debt obligations. The Trust may also invest in Senior Loans of Borrowers that have obtained bridge loans from other parties. A Borrower’s use of bridge loans involves a risk that the Borrower may be unable to locate permanent financing to replace the bridge loan, which may impair the Borrower’s perceived creditworthiness.

The Trust will be subject to the risk that collateral securing a loan will decline in value or have no value. Such a decline, whether as a result of bankruptcy proceedings or otherwise, could cause the Senior Loan to be undercollateralized or unsecured. In most credit agreements, there is no formal requirement to pledge additional collateral. In addition, the Trust may invest in Senior Loans guaranteed by, or secured by assets of, shareholders or owners, even if the Senior Loans are not otherwise collateralized by assets of the Borrower; provided, however, that such guarantees are fully secured. There may be temporary periods when the principal asset held by a Borrower is the stock of a related company, which may not legally be pledged to secure a Senior Loan. On occasions when such stock cannot be pledged, the Senior Loan will be temporarily unsecured until the stock can be pledged or is exchanged for or replaced by other assets, which will be pledged as security for the Senior Loan. However, the Borrower’s ability to dispose of such securities, other than in connection with such pledge or replacement, will be strictly limited for the protection of the holders of Senior Loans and, indirectly, Senior Loans themselves.

If a Borrower becomes involved in bankruptcy proceedings, a court may invalidate the Trust’s security interest in the loan collateral or subordinate the Trust’s rights under the Senior Loan to the interests of the Borrower’s unsecured creditors or cause interest previously paid to be refunded to the Borrower. If a court required interest to be refunded, it could negatively affect the Trust’s performance. Such action by a court could be based, for example, on a “fraudulent conveyance” claim to the effect that the Borrower did not receive fair consideration for granting the security interest in the loan collateral to the Trust. For Senior Loans made in connection with a highly leveraged transaction, consideration for granting a security interest may be deemed inadequate if the proceeds of the Loan were not received or retained by the Borrower, but were instead paid to other persons (such as shareholders of the Borrower) in an amount that left the Borrower insolvent or without sufficient working capital. There are also other events, such as the failure to perfect a security interest due to faulty documentation or faulty official filings, which could lead to the invalidation of the Trust’s security interest in loan collateral. If the Trust’s security interest in loan collateral is invalidated or the Senior Loan is subordinated to other debt of a Borrower in bankruptcy or other proceedings, the Trust would have substantially lower recovery, and perhaps no recovery on the full amount of the principal and interest due on the Senior Loan.

Loans are also subject to the risk that their value will decline in a rising interest rate environment. This risk is mitigated for floating-rate loans, where the interest rate payable on the loan resets periodically by reference to a base lending rate. The base lending rate usually is the London Interbank Offered Rate (“LIBOR”), the Federal Reserve federal funds rate, the prime rate or other base lending rates used by commercial lenders. LIBOR usually is an average of the interest rates quoted by several designated banks as the rates at which they pay interest to major depositors in the London interbank market on U.S. dollar-denominated deposits.

Eaton Vance Senior Income Trust

SAI dated [_____], 2018

Many financial instruments use or may use a floating rate based on LIBOR, which is the offered rate for short-term Eurodollar deposits between major international banks. On July 27, 2017, the head of the United Kingdom’s Financial Conduct Authority announced a desire to phase out the use of LIBOR by the end of 2021. Due to the recency of this announcement, there remains uncertainty regarding the future utilization of LIBOR and the nature of any replacement rate. As such, the potential effect of a transition away from LIBOR on the Trust or the financial instruments in which the Trust invests cannot yet be determined.

The Trust may acquire warrants and other equity securities as part of a unit combining a Senior Loan and equity securities of a Borrower or its affiliates. The acquisition of such equity securities will only be incidental to the Trust’s purchase of a Senior Loan. The Trust may also acquire equity securities or debt securities (including non-dollar denominated debt securities) issued in exchange for a Senior Loan or issued in connection with the debt restructuring or reorganization of a Borrower, if such acquisition, in the judgment of the Adviser, may enhance the value of a Senior Loan or if such acquisition would otherwise be consistent with the Trust’s investment policies.

Debtor-in-Possession Financing. The Trust may invest in debtor-in-possession financings (commonly called “DIP financings”). DIP financings are arranged when an entity seeks the protections of the bankruptcy court under chapter 11 of the U.S. Bankruptcy Code. These financings allow the entity to continue its business operations while reorganizing under chapter 11. Such financings are senior liens on unencumbered security (i.e., security not subject to other creditors’ claims). There is a risk that the entity will not emerge from chapter 11 and be forced to liquidate its assets under chapter 7 of the Bankruptcy Code. In such event, the Trust’s only recourse will be against the property securing the DIP financing.

Regulatory Changes. To the extent that legislation or state or federal regulators that regulate certain financial institutions impose additional requirements or restrictions with respect to the ability of such institutions to make loans, particularly in connection with highly leveraged transactions, the availability of Senior Loans for investment may be adversely affected. Further, such legislation or regulation could depress the market value of Senior Loans.

Junior Loans. The Trust may invest in secured and unsecured subordinated loans, second lien loans and subordinated bridge loans (“Junior Loans”). Second lien loans are generally second in line in terms of repayment priority. A second lien loan may have a claim on the same collateral pool as the first lien or it may be secured by a separate set of assets, such as property, plants, or equipment. Second lien loans generally give investors priority over general unsecured creditors in the event of an asset sale.

Junior Loans are subject to the same general risks inherent to any loan investment, including credit risk, market and liquidity risk, and interest rate risk. Due to their lower place in the Borrower’s capital structure and possible unsecured status, Junior Loans involve a higher degree of overall risk than Senior Loans of the same Borrower.

The Trust may purchase Junior Loan interests either in the form of an assignment or a loan participation. As the purchaser of an assignment, the Trust would typically succeed to all of the rights and obligations of the assigning investor under the loan documents. In contrast, loan participations typically result in the purchaser having a contractual relationship only with the seller of the loan interest, not with the Borrower. As a result, the loan is not transferred to the loan participant. The loan participant’s right to receive payments from the Borrower derives from the seller of the loan participation. The loan participant will generally have no right to enforce compliance by the Borrower with the terms of the loan agreement. Lastly, the loan participant’s voting rights may be limited.

Bridge Loans. Bridge loans or bridge facilities are short-term loan arrangements (e.g., 12 to 18 months) typically made by a Borrower in anticipation of intermediate-term or long-term permanent financing. Most bridge loans are structured as floating-rate debt with step-up provisions under which the interest rate on the bridge loan rises the longer the loan remains outstanding. In addition, bridge loans commonly contain a conversion feature that allows the bridge loan investor to convert its loan interest into senior exchange notes if the loan has not been prepaid in full on or prior to its maturity date. Bridge loans may be subordinate to other debt and may be secured or unsecured. Like any loan, bridge loans involve credit risk. Bridge loans are generally made with the expectation that the Borrower will be able to obtain permanent financing in the near future. Any delay in obtaining permanent financing subjects the bridge loan investor to increased risk. A Borrower’s use of bridge loans also involves the risk that the Borrower may be unable to locate permanent financing to replace the bridge loan, which may impair the Borrower’s perceived creditworthiness. From time to time, the Trust may make a commitment to participate in a bridge loan facility, obligating itself to participate in the facility if it funds. In return for this commitment, the Trust receives a fee.

Eaton Vance Senior Income Trust

SAI dated [_____], 2018

Credit Quality. Many Senior Loans in which the Trust may invest are of below investment grade credit quality. Accordingly, these Senior Loans are subject to similar or identical risks and other characteristics described below in relation to Non-Investment Grade Bonds.

NON-INVESTMENT GRADE BONDS

Investments in Non-Investment Grade Bonds generally provide greater income and increased opportunity for capital appreciation than investments in higher quality securities, but they also typically entail greater price volatility and principal and income risk, including the possibility of issuer default and bankruptcy. Non-Investment Grade Bonds are regarded as predominantly speculative with respect to the issuer’s continuing ability to meet principal and interest payments. Debt securities in the lowest investment grade category also may be considered to possess some speculative characteristics by certain rating agencies. In addition, analysis of the creditworthiness of issuers of Non-Investment Grade Bonds may be more complex than for issuers of higher quality securities.

Non-Investment Grade Bonds may be more susceptible to real or perceived adverse economic and competitive industry conditions than investment grade securities. A projection of an economic downturn or of a period of rising interest rates, for example, could cause a decline in Non-Investment Grade Bond prices because the advent of recession could lessen the ability of an issuer to make principal and interest payments on its debt obligations. If an issuer of Non-Investment Grade Bonds defaults, in addition to risking payment of all or a portion of interest and principal, the Trust may incur additional expenses to seek recovery. In the case of Non-Investment Grade Bonds structured as zero-coupon, step-up or payment-in-kind securities, their market prices will normally be affected to a greater extent by interest rate changes, and therefore tend to be more volatile than securities that pay interest currently and in cash. Eaton Vance seeks to reduce these risks through diversification, credit analysis and attention to current developments in both the economy and financial markets.

The secondary market on which Non-Investment Grade Bonds are traded may be less liquid than the market for investment grade securities. Less liquidity in the secondary trading market could adversely affect the net asset value of the Common Shares. Adverse publicity and investor perceptions, whether or not based on fundamental analysis, may decrease the values and liquidity of Non-Investment Grade Bonds, especially in a thinly traded market. When secondary markets for Non-Investment Grade Bonds are less liquid than the market for investment grade securities, it may be more difficult to value the securities because such valuation may require more research, and elements of judgment may play a greater role in the valuation because there is no reliable, objective data available. During periods of thin trading in these markets, the spread between bid and asked prices is likely to increase significantly and the Trust may have greater difficulty selling these securities. The Trust will be more dependent on Eaton Vance’s research and analysis when investing in Non-Investment Grade Bonds. Eaton Vance seeks to minimize the risks of investing in all securities through in-depth credit analysis and attention to current developments in interest rate and market conditions.

A general description of the ratings of securities by S&P, Fitch and Moody’s is set forth in Appendix A to this SAI. Such ratings represent these rating organizations’ opinions as to the quality of the securities they rate. It should be emphasized, however, that ratings are general and are not absolute standards of quality. Consequently, debt obligations with the same maturity, coupon and rating may have different yields while obligations with the same maturity and coupon may have the same yield. For these reasons, the use of credit ratings as the sole method of evaluating Non-Investment Grade Bonds can involve certain risks. For example, credit ratings evaluate the safety or principal and interest payments, not the market value risk of Non-Investment Grade Bonds. Also, credit rating agencies may fail to change credit ratings in a timely fashion to reflect events since the security was last rated. Eaton Vance does not rely solely on credit ratings when selecting securities for the Trust, and develops its own independent analysis of issuer credit quality.

In the event that a rating agency or Eaton Vance downgrades its assessment of the credit characteristics of a particular issue, the Trust is not required to dispose of such security. In determining whether to retain or sell a downgraded security, Eaton Vance may consider such factors as Eaton Vance’s assessment of the credit quality of the issuer of such security, the price at which such security could be sold and the rating, if any, assigned to such security by other rating agencies. However, analysis of the creditworthiness of issuers of Non-Investment Grade Bonds may be more complex than for issuers of high quality debt securities.

OTHER INVESTMENTS

Convertible Securities. The Trust may invest in convertible securities. A convertible security is a bond, debenture, note, preferred security, or other security that entitles the holder to acquire common stock or other equity securities of the same or a different issuer. A convertible security entitles the holder to receive interest paid or accrued or the dividend paid on such security until the convertible security matures or is redeemed, converted or exchanged. Before conversion, convertible securities have characteristics similar to nonconvertible income securities in that they ordinarily provide a

Eaton Vance Senior Income Trust

SAI dated [_____], 2018

stable stream of income with generally higher yields than those of common stocks of the same or similar issuers, but lower yields than comparable nonconvertible securities. The value of a convertible security is influenced by changes in interest rates, with investment value declining as interest rates increase and increasing as interest rates decline. The credit standing of the issuer and other factors also may have an effect on the convertible security’s investment value. A convertible security ranks senior to common stock in a corporation’s capital structure but is usually subordinated to comparable nonconvertible securities. Convertible securities may be purchased for their appreciation potential when they yield more than the underlying securities at the time of purchase or when they are considered to present less risk of principal loss than the underlying securities. Generally speaking, the interest or dividend yield of a convertible security is somewhat less than that of a non-convertible security of similar quality issued by the same company. A convertible security may be subject to redemption at the option of the issuer at a price established in the convertible security’s governing instrument.

Convertible securities are issued and traded in a number of securities markets. Even in cases where a substantial portion of the convertible securities held by the Trust are denominated in U.S. dollars, the underlying equity securities may be quoted in the currency of the country where the issuer is domiciled. As a result, fluctuations in the exchange rate between the currency in which the debt security is denominated and the currency in which the share price is quoted will affect the value of the convertible security. With respect to convertible securities denominated in a currency different from that of the underlying equity securities, the conversion price may be based on a fixed exchange rate established at the time the securities are issued, which may increase the effects of currency risk.

Holders of convertible securities generally have a claim on the assets of the issuer prior to the common stockholders but may be subordinated to other debt securities of the same issuer. Certain convertible debt securities may provide a put option to the holder, which entitles the holder to cause the securities to be redeemed by the issuer at a premium over the stated principal amount of the debt securities under certain circumstances. Certain convertible securities may include loss absorption characteristics that make the securities more equity-like. This is particularly true of convertible securities issued by companies in the financial services sector.

Synthetic convertible securities may include either cash-settled convertibles or manufactured convertibles. Cash-settled convertibles are instruments that are created by the issuer and have the economic characteristics of traditional convertible securities but may not actually permit conversion into the underlying equity securities in all circumstances. As an example, a private company may issue a cash-settled convertible that is convertible into common stock only if the company successfully completes a public offering of its common stock prior to maturity and otherwise pays a cash amount to reflect any equity appreciation. Manufactured convertibles are created by the investment adviser or another party by combining separate securities that possess one of the two principal characteristics of a convertible security, i.e., fixed-income (“fixed-income component”) or a right to acquire equity securities (“convertibility component”). The fixed-income component is achieved by investing in nonconvertible fixed-income securities, such as nonconvertible bonds, preferred securities and money market instruments. The convertibility component is achieved by investing in call options, warrants, or other securities with equity conversion features (“equity features”) granting the holder the right to purchase a specified quantity of the underlying stocks within a specified period of time at a specified price or, in the case of a stock index option, the right to receive a cash payment based on the value of the underlying stock index. A manufactured convertible differs from traditional convertible securities in several respects. Unlike a traditional convertible security, which is a single security that has a unitary market value, a manufactured convertible is comprised of two or more separate securities, each with its own market value. Therefore, the total “market value” of such a manufactured convertible is the sum of the values of its fixed-income component and its convertibility component. More flexibility is possible in the creation of a manufactured convertible than in the purchase of a traditional convertible security. Because many corporations have not issued convertible securities, the investment adviser may combine a fixed-income instrument and an equity feature with respect to the stock of the issuer of the fixed-income instrument to create a synthetic convertible security otherwise unavailable in the market. The investment adviser may also combine a fixed-income instrument of an issuer with an equity feature with respect to the stock of a different issuer when the investment adviser believes such a manufactured convertible would better promote the Trust’s objective than alternative investments. For example, the investment adviser may combine an equity feature with respect to an issuer’s stock with a fixed-income security of a different issuer in the same industry to diversify the Trust’s credit exposure, or with a U.S. Treasury instrument to create a manufactured convertible with a higher credit profile than a traditional convertible security issued by that issuer. A manufactured convertible also is a more flexible investment in that its two components may be purchased separately and, upon purchasing the separate securities, “combined” to create a manufactured convertible. For example, the Trust may purchase a warrant for eventual inclusion in a manufactured convertible while postponing the purchase of a suitable bond to pair with the warrant pending development of more favorable market conditions. The value of a manufactured convertible may respond to certain market fluctuations differently from a traditional convertible security with similar characteristics. For example, in the event the Trust created a manufactured convertible by combining a short-term U.S. Treasury instrument and a call option on a stock, the manufactured convertible would be expected to outperform a traditional convertible of similar maturity that is convertible into that stock during periods when Treasury instruments outperform corporate fixed-income securities and underperform during periods when corporate fixed-income securities outperform Treasury instruments.

Eaton Vance Senior Income Trust

SAI dated [_____], 2018

Fixed-Income Securities. Fixed-income securities include bonds, preferred, preference and convertible securities, notes, debentures, asset-backed securities (including those backed by mortgages), loan participations and assignments, equipment lease certificates, equipment trust certificates and conditional sales contracts. Generally, issuers of fixed-income securities pay investors periodic interest and repay the amount borrowed either periodically during the life of the security and/or at maturity. Some fixed-income securities, such as zero coupon bonds, do not pay current interest, but are purchased at a discount from their face values, and values accumulate over time to face value at maturity. The market prices of fixed-income securities fluctuate depending on such factors as interest rates, credit quality and maturity. In general, market prices of fixed-income securities decline when interest rates rise and increase when interest rates fall. Fixed-income securities are subject to risk factors such as sensitivity to interest rate and real or perceived changes in economic conditions, payment expectations, liquidity and valuation. Fixed-income securities with longer maturities (for example, over ten years) are more affected by changes in interest rates and provide less price stability than securities with short-term maturities (for example, one to ten years). Fixed-income securities bear the risk of principal and interest default by the issuer, which will be greater with higher yielding, lower grade securities. During an economic downturn, the ability of issuers to service their debt may be impaired. The rating assigned to a fixed-income security by a rating agency does not reflect assessment of the volatility of the security’s market value or of the liquidity of an investment in the securities. Credit ratings are based largely on the issuer’s historical financial condition and a rating agency’s investment analysis at the time of rating, and the rating assigned to any particular security is not necessarily a reflection of the issuer’s current financial condition. Credit quality can change from time to time, and recently issued credit ratings may not fully reflect the actual risks posed by a particular high yield security. In addition to lower rated securities, the Trust may also invest in higher rated securities. For a description of corporate ratings, see Appendix A.

Repurchase Agreements. The Trust may enter into repurchase agreements (the purchase of a security coupled with an agreement to resell at a higher price) with respect to its permitted investments. In the event of the bankruptcy of the other party to a repurchase agreement, the Trust might experience delays in recovering its cash. To the extent that, in the meantime, the value of the securities the Trust purchased may have decreased, the Trust could experience a loss. Repurchase agreements that mature in more than seven days will be treated as illiquid. The Trust’s repurchase agreements will provide that the value of the collateral underlying the repurchase agreement will always be at least equal to the repurchase price, including any accrued interest earned on the agreement, and will be marked to market daily.

When the Trust enters into a reverse repurchase agreement, any fluctuations in the market value of either the securities transferred to another party or the securities in which the proceeds may be invested would affect the market value of the Trust's assets. As a result, such transactions may increase fluctuations in the market value of the Trust's assets. While there is a risk that large fluctuations in the market value of the Trust's assets could affect net asset value, this risk is not significantly increased by entering into reverse repurchase agreements, in the opinion of the Adviser. Because reverse repurchase agreements may be considered to be the practical equivalent of borrowing funds, they constitute a form of leverage. The SEC views reverse repurchase transactions as collateralized borrowings by a fund. Such agreements will be treated as subject to investment restrictions regarding “borrowings.” If the Trust reinvests the proceeds of a reverse repurchase agreement at a rate lower than the cost of the agreement, entering into the agreement will lower the Trust's yield.

Zero Coupon and Deep Discount Bonds and Payment-in-Kind (“PIK”) Securities. Zero coupon bonds are debt obligations that do not require the periodic payment of interest and are issued at a significant discount from face value. The discount approximates the total amount of interest the bonds will accrue and compound over the period until maturity at a rate of interest reflecting the market rate of the security at the time of purchase. The effect of owning debt obligations that do not make current interest payments is that a fixed yield is earned not only on the original investment but also, in effect, on all discount accretion during the life of the debt obligation. This implicit reinvestment of earnings at a fixed rate eliminates the risk of being unable to invest distributions at a rate as high as the implicit yield on the zero coupon bond, but at the same time eliminates the holder’s ability to reinvest at higher rates in the future. Deep discount bonds also are issued at a discount from face value, but may make periodic interest payments at a below market interest rate.

Eaton Vance Senior Income Trust

SAI dated [_____], 2018

PIK securities generally carry higher interest rates compared to bonds that make cash payments of interest to reflect their payment deferral and increased credit risk. PIK interest has the effect of generating investment income and increasing the incentive fees, if any, payable at a compounding rate. Generally, the deferral of PIK interest increases the loan to value ratio.

Bonds and preferred stocks that make “in-kind” payments and other securities that do not pay regular income distributions may experience greater volatility in response to interest rate changes and issuer developments. PIK securities generally involve significantly greater credit risk than coupon loans because the Trust receives no cash payments until the maturity date or a specified cash payment date. Even if accounting conditions are met for accruing income payable at a future date under a PIK bond, the issuer could still default when the collection date occurs at the maturity of or payment date for the PIK bond. PIK bonds may be difficult to value accurately because they involve ongoing judgments as to the collectability of the deferred payments and the value of any associated collateral. If the issuer of a PIK security defaults, the Trust may lose its entire investment.

The Trust is required to accrue income from zero coupon and deep discount bonds and PIK securities on a current basis, even though it does not receive that income currently in cash, and the Trust is required to distribute that income for each taxable year. Such distributions could reduce the Trust’s cash position and require it to sell securities and incur a gain or loss at a time it may not otherwise want to in order to provide the cash necessary for these distributions.

Indexed Securities. The Trust may invest in securities that fluctuate in value with an index. Such securities generally will either be issued by the U.S. Government or one of its agencies or instrumentalities or, if privately issued, collateralized by mortgages that are insured, guaranteed or otherwise backed by the U.S. Government, its agencies or instrumentalities. The interest rate or, in some cases, the principal payable at the maturity of an indexed security may change positively or inversely in relation to one or more interest rates, financial indices, securities prices or other financial indicators (“reference prices”). An indexed security may be leveraged to the extent that the magnitude of any change in the interest rate or principal payable on an indexed security is a multiple of the change in the reference price. Thus, indexed securities may decline in value due to adverse market changes in reference prices. Because indexed securities derive their value from another instrument, security or index, they are considered derivative debt securities, and are subject to different combinations of prepayment, extension, interest rate and/or other market risks.

Short Sales. The Trust may utilize short sales for hedging purposes. A short sale is effected by selling a security which the Trust does not own, or, if the Trust does own the security, is not to be delivered upon consummation of the sale. The Trust may engage in short sales “against the box” (i.e., short sales of securities the Trust already owns) for hedging purposes. If the price of the security in the short sale decreases, the Trust will realize a profit to the extent that the short sale price for the security exceeds the market price. If the price of the security increases, the Trust will realize a loss to the extent that the market price exceeds the short sale price. Selling securities short runs the risk of losing an amount greater than the initial investment therein.

Purchasing securities to close out the short position can itself cause the price of the securities to rise further, thereby exacerbating the loss. Short-selling exposes the Trust to unlimited risk with respect to that security due to the lack of an upper limit on the price to which an instrument can rise. Although the Trust reserves the right to utilize short sales, the Adviser is under no obligation to utilize short-sales at all.

Foreign Investments. The Trust may invest in U.S. dollar denominated securities of non-U.S. issuers. Because foreign companies are not subject to uniform accounting, auditing and financial reporting standards, practices and requirements comparable to those applicable to U.S. companies, there may be less publicly available information about a foreign company than about a domestic company. Volume and liquidity in most foreign debt markets is less than in the United States and securities of some foreign companies are less liquid and more volatile than securities of comparable U.S. companies. There is generally less government supervision and regulation of securities exchanges, broker-dealers and listed companies than in the United States. Mail service between the United States and foreign countries may be slower or less reliable than within the United States, thus increasing the risk of delayed settlements of portfolio transactions or loss of certificates for portfolio securities. Payment for securities before delivery may be required. In addition, with respect to certain foreign countries, there is the possibility of expropriation or confiscatory taxation, political or social instability, or diplomatic developments that could affect investments in those countries. Moreover, individual foreign economies may differ favorably or unfavorably from the U.S. economy in such respects as growth of gross national product, rate of inflation, capital reinvestment, resource self-sufficiency and balance of payments position. Foreign securities markets, while growing in volume and sophistication, are generally not as developed as those in the United States, and securities of some foreign issuers (particularly those located in developing countries) may be less liquid and more volatile than securities of comparable U.S. companies.

Eaton Vance Senior Income Trust

SAI dated [_____], 2018

American Depositary Receipts (“ADRs”), European Depositary Receipts (“EDRs”) and Global Depositary Receipts (“GDRs”) may be purchased. ADRs, EDRs and GDRs are certificates evidencing ownership of shares of a foreign issuer and are alternatives to purchasing directly the underlying foreign securities in their national markets and currencies. However, they continue to be subject to many of the risks associated with investing directly in foreign securities. These risks include foreign exchange risk as well as the political and economic risks of the underlying issuer’s country. ADRs, EDRs and GDRs may be sponsored or unsponsored. Unsponsored receipts are established without the participation of the issuer. Unsponsored receipts may involve higher expenses, they may not pass through voting or other shareholder rights, and they may be less liquid.

Derivative Instruments. Derivative instruments (which derive their value from another instrument, security or index) may be used for risk management purposes, such as hedging against fluctuations in Senior Loans and other securities prices or interest rates. Such transactions in derivative instruments may include the purchase or sale of futures contracts on securities, indices and other financial instruments, credit-linked notes, tranches of collateralized loan obligations and/or collateralized debt obligations, options on futures contracts, and exchange-traded and over-the-counter options on securities or indices, and interest rate, total return and credit default swaps. The Trust may enter into derivatives transactions with respect to any security or other instrument in which it is permitted to invest. The Trust incurs costs in opening and closing derivatives positions.

The Trust may use derivative instruments and trading strategies, including the following:

Options on Securities Indices and Currencies. The Trust may engage in transactions in exchange traded and over-the-counter (“OTC”) options. In general, exchange-traded options have standardized exercise prices and expiration dates and require the parties to post margin against their obligations, and the performance of the parties' obligations in connection with such options is guaranteed by the exchange or a related clearing corporation. OTC options have more flexible terms negotiated between the buyer and the seller, but generally do not require the parties to post margin and are subject to greater credit risk. The ability of the Trust to transact business with any one or any number of counterparties, the lack of any independent evaluation of the counterparties or their financial capabilities and the absence of a regulated market to facilitate settlement, may increase the potential for losses to the Trust. OTC options also involve greater liquidity risk. This risk may be increased in times of financial stress if the trading market for OTC options becomes limited. The Staff of the SEC takes the position that certain purchased OTC options, and assets used as cover for written OTC options, are illiquid.

Call Options. A purchased call option gives the Trust the right to buy, and obligates the seller to sell, the underlying instrument at the exercise price at any time during the option period. The Trust also may purchase and sell call options on indices. Index options are similar to options on securities except that, rather than taking or making delivery of securities underlying the option at a specified price upon exercise, an index option gives the holder the right to receive cash upon exercise of the option if the level of the index upon which the option is based is greater than the exercise price of the option.

The Trust also is authorized to write (i.e., sell) call options and to enter into closing purchase transactions with respect to certain of such options. A covered call option is an option in which the Trust, in return for a premium, gives another party a right to buy specified securities owned by the Trust at a specified future date and price set at the time of the contract.

The principal reason for writing call options is the attempt to realize, through the receipt of premiums, a greater return than would be realized on the securities alone. By writing covered call options, the Trust gives up the opportunity, while the option is in effect, to profit from any price increase in the underlying security above the option exercise price. In addition, the Trust's ability to sell the underlying security will be limited while the option is in effect unless the Trust enters into a closing purchase transaction. A closing purchase transaction cancels out the Trust's position as the writer of an option by means of an offsetting purchase of an identical option prior to the expiration of the option it has written. Covered call options also serve as a partial hedge to the extent of the premium received against the price of the underlying security declining.

Put Options. The Trust is authorized to purchase put options to seek to hedge against a decline in the value of its securities or to enhance its return. By buying a put option, the Trust acquires a right to sell the underlying securities or instruments at the exercise price, thus limiting the Trust's risk of loss through a decline in the market value of the securities or instruments until the put option expires. The amount of any appreciation in the value of the underlying securities or instruments will be partially offset by the amount of the premium paid for the put option and any related transaction costs. Prior to its expiration, a put option may be sold in a closing sale transaction and profit or loss from the sale will depend on whether the amount received is more or less than the premium paid for the put option plus the related transaction costs. A closing sale transaction cancels out the Trust's position as the purchaser of an option by means of an offsetting sale of an identical option prior to the expiration of the option it has purchased. The Trust also may purchase uncovered put options.

Eaton Vance Senior Income Trust

SAI dated [_____], 2018

The Trust also has authority to write (i.e., sell) put options. The Trust will receive a premium for writing a put option, which increases the Trust's return. The Trust has the obligation to buy the securities or instruments at an agreed upon price if the price of the securities or instruments decreases below the exercise price. There are several risks associated with transactions in options on securities and indexes. For example, there are significant differences between the securities and options markets that could result in an imperfect correlation between these markets, causing a given transaction not to achieve its objectives. In addition, a liquid secondary market for particular options, whether traded OTC or on a national securities exchange may be absent for reasons which include the following: there may be insufficient trading interest in certain options; restrictions may be imposed by a national securities exchange on opening transactions or closing transactions or both; trading halts, suspensions or other restrictions may be imposed with respect to particular classes or series of options or underlying securities; unusual or unforeseen circumstances may interrupt normal operations on a national securities exchange; the facilities of a national securities exchange or the Options Clearing Corporation (the “OCC”) may not at all times be adequate to handle current trading volume; or one or more national securities exchanges could, for economic or other reasons, decide or be compelled at some future date to discontinue the trading of options (or a particular class or series of options), in which event the secondary market on that national securities exchange (or in that class or series of options) would cease to exist, although outstanding options that had been issued by the OCC as a result of trades on that national securities exchange would continue to be exercisable in accordance with their terms.

Options positions are marked to market daily. The value of options is affected by changes in the value and dividend rates of the securities underlying the option or represented in the index underlying the option, changes in interest rates, changes in the actual or perceived volatility of the relevant index or market and the remaining time to the options’ expiration, as well as trading conditions in the options market. The hours of trading for options may not conform to the hours during which the underlying securities are traded. To the extent that the options markets close before the markets for the underlying securities, significant price and rate movements can take place in the underlying markets that would not be reflected concurrently in the options markets.

Futures. The Trust may engage in transactions in futures and options on futures. Futures are standardized, exchange-traded contracts. Futures contracts on securities obligate a purchaser to take delivery, and a seller to make delivery, of a specific amount of the financial instrument called for in the contract at a specified future date at a specified price. An index futures contract obligates the purchaser to take, and a seller to deliver an amount of cash equal to a specific dollar amount times the difference between the value of a specific index at the close of the last trading day of the contract and the price at which the agreement is made. No physical delivery of the underlying securities in the index is made. It is the practice of holders of futures contracts to close out their positions on or before the expiration date by use of offsetting contract positions, and physical delivery of financial instruments or delivery of cash, as applicable, is thereby avoided. No price is paid upon entering into a futures contract. Rather, upon purchasing or selling a futures contract the Trust is required to deposit collateral (“margin”) equal to a percentage (generally less than 10%) of the contract value. Each day thereafter until the futures position is closed, the Trust will pay additional margin representing any loss experienced as a result of the futures position the prior day or be entitled to a payment representing any profit experienced as a result of the futures position the prior day. Futures involve substantial leverage risk. The sale of a futures contract limits the Trust's risk of loss from a decline in the market value of portfolio holdings correlated with the futures contract prior to the futures contract's expiration date. In the event the market value of the Trust holdings correlated with the futures contract increases rather than decreases, however, the Trust will realize a loss on the futures position and a lower return on the Trust holdings than would have been realized without the purchase of the futures contract.

The purchase of a futures contract may protect the Trust from having to pay more for securities as a consequence of increases in the market value for such securities during a period when the Trust was attempting to identify specific securities in which to invest in a market the Trust believes to be attractive. In the event that such securities decline in value or the Trust determines not to complete an anticipatory hedge transaction relating to a futures contract, however, the Trust may realize a loss relating to the futures position.

The Trust is also authorized to purchase or sell call and put options on futures contracts including financial futures and stock indices. Generally, these strategies would be used under the same market and market sector conditions (i.e., conditions relating to specific types of investments) in which the Trust entered into futures transactions. The Trust may purchase put options or write call options on futures contracts and stock indices in lieu of selling the underlying futures contract in anticipation of a decrease in the market value of its securities. Similarly, the Trust can purchase call options, or write put options on futures contracts and stock indices, as a substitute for the purchase of such futures to hedge against the increased cost resulting from an increase in the market value of securities which the Trust intends to purchase.

Eaton Vance Senior Income Trust

SAI dated [_____], 2018

Risks Associated with Futures. The primary risks associated with the use of futures contracts and options are (a) the imperfect correlation between the change in market value of the instruments held by the Trust and the price of the futures contract or option; (b) possible lack of a liquid secondary market for a futures contract and the resulting inability to close a futures contract when desired; (c) losses caused by unanticipated market movements, which are potentially unlimited; (d) the investment adviser’s inability to predict correctly the direction of securities prices, interest rates, currency exchange rates and other economic factors; and (e) the possibility that the counterparty will default in the performance of its obligations.

The Trust has claimed an exclusion from the definition of the term Commodity Pool Operator (“CPO”) under the Commodity Exchange Act and therefore is not subject to registration as a CPO.

Foreign Currency Transactions. The Trust may engage in spot transactions and forward foreign currency exchange contracts and currency swaps, purchase and sell options on currencies and purchase and sell currency futures and related options thereon (collectively, “Currency Instruments”) for purposes of hedging against the decline in the value of currencies in which its portfolio holdings are denominated against the U.S. dollar or, to seek to enhance returns. Such transactions could be effected with respect to hedges on foreign dollar denominated securities owned by the Trust, sold by the Trust but not yet delivered, or committed or anticipated to be purchased by the Trust.

As measured in U.S. dollars, the value of assets denominated in foreign currencies may be affected favorably or unfavorably by changes in foreign currency rates and exchange control regulations. Currency exchange rates can also be affected unpredictably by intervention by U.S. or foreign governments or central banks, or the failure to intervene, or by currency controls or political developments in the United States or abroad. If the U.S. dollar rises in value relative to a foreign currency, a security denominated in that foreign currency will be worth less in U.S. dollars. If the U.S. dollar decreases in value relative to a foreign currency, a security denominated in that foreign currency will be worth more in U.S. dollars. A devaluation of a currency by a country’s government or banking authority will have a significant impact on the value of any investments denominated in that currency. Foreign currency exchange transactions may be conducted on a spot (i.e., cash) basis at the spot rate prevailing in the foreign currency exchange market or through entering into derivative currency transactions. Currency transactions are subject to the risk of a number of complex political and economic factors applicable to the countries issuing the underlying currencies. Furthermore, unlike trading in most other types of instruments, there is no systematic reporting of last sale information with respect to the foreign currencies underlying the derivative currency transactions. As a result, available information may not be complete. In an over-the-counter trading environment, there are no daily price fluctuation limits.

Forward Foreign Currency Exchange Contracts. Forward foreign currency exchange contracts are OTC contracts to purchase or sell a specified amount of a specified currency or multinational currency unit at a price and future date set at the time of the contract. Spot foreign exchange transactions are similar but require current, rather than future, settlement. The Trust will enter into foreign exchange transactions for purposes of hedging either a specific transaction or the Trust position or, to seek to enhance returns. Proxy hedging is often used when the currency to which the Trust is exposed is difficult to hedge or to hedge against the dollar. Proxy hedging entails entering into a forward contract to sell a currency whose changes in value are generally considered to be linked to a currency or currencies in which some or all of the Trust's securities are, or are expected to be, denominated, and to buy U.S. dollars. Proxy hedging involves some of the same risks and considerations as other transactions with similar instruments. Currency transactions can result in losses to the Trust if the currency being hedged fluctuates in value to a degree or in a direction that is not anticipated. In addition, there is the risk that the perceived linkage between various currencies may not be present or may not be present during the particular time that the Trust is engaged in proxy hedging. The Trust may also cross-hedge currencies by entering into forward contracts to sell one or more currencies that are expected to decline in value relative to other currencies to which the Trust has or in which the Trust expects to have portfolio exposure. Some of the forward foreign currency contracts entered into by the Trust are classified as non-deliverable forwards (“NDF”). NDFs are cash-settled, short-term forward contracts that may be thinly traded or are denominated in non-convertible foreign currency, where the profit or loss at the time at the settlement date is calculated by taking the difference between the agreed upon exchange rate and the spot rate at the time of settlement, for an agreed upon notional amount of funds. NDFs are commonly quoted for time periods of one month up to two years, and are normally quoted and settled in U.S. dollars. They are often used to gain exposure to and/or hedge exposure to foreign currencies that are not internationally traded.

Currency Futures. The Trust may also seek to enhance returns or hedge against the decline in the value of a currency through use of currency futures or options thereon. Currency futures are similar to forward foreign exchange transactions except that futures are standardized, exchange-traded contracts while forward foreign exchange transactions are traded in the OTC market. Currency futures involve substantial currency risk, and also involve leverage risk.

Eaton Vance Senior Income Trust

SAI dated [_____], 2018

Currency Options. The Trust may also seek to enhance returns or hedge against the decline in the value of a currency through the use of currency options. Currency options are similar to options on securities. For example, in consideration for an option premium the writer of a currency option is obligated to sell (in the case of a call option) or purchase (in the case of a put option) a specified amount of a specified currency on or before the expiration date for a specified amount of another currency. The Trust may engage in transactions in options on currencies either on exchanges or OTC markets. Currency options involve substantial currency risk, and may also involve credit, leverage or liquidity risk.

Risk Factors in Hedging Foreign Currency. Hedging transactions involving Currency Instruments involve substantial risks, including correlation risk. Although Currency Instruments will be used with the intention of hedging against adverse currency movements, transactions in Currency Instruments involve the risk that anticipated currency movements will not be accurately predicted and that the Trust's hedging strategies will be ineffective. To the extent that the Trust hedges against anticipated currency movements that do not occur, the Trust may realize losses and decrease its total return as the result of its hedging transactions. Furthermore, the Trust will only engage in hedging activities from time to time and may not be engaging in hedging activities when movements in currency exchange rates occur.

Swap Agreements. Swap agreements are two-party contracts entered into primarily by institutional investors for periods ranging from a few weeks to more than one year. In a standard “swap” transaction, two parties agree to exchange the returns (or differentials in rates of return) earned or realized on a particular predetermined reference instrument or instruments, which can be adjusted for an interest rate factor. The gross returns to be exchanged or “swapped” between the parties are generally calculated with respect to a “notional amount” (i.e., the return on or increase in value of a particular dollar amount invested at a particular interest rate or in a “basket” of securities representing a particular index). Other types of swap agreements may calculate the obligations of the parties to the agreement on a “net basis.” Consequently, a party’s current obligations (or rights) under a swap agreement will generally be equal only to the net amount to be paid or received under the agreement based on the relative values of the positions held by each party to the agreement (the “net amount”).

Whether the use of swap agreements will be successful will depend on the investment adviser's ability to predict correctly whether certain types of reference instruments are likely to produce greater returns than other instruments. Swap agreements may be subject to contractual restrictions on transferability and termination and they may have terms of greater than seven days. The Trust’s obligations under a swap agreement will be accrued daily (offset against any amounts owed to the Trust under the swap). Developments in the swaps market, including government regulation, could adversely affect the Trust’s ability to terminate existing swap agreements or to realize amounts to be received under such agreements, as well as to participate in swap agreements in the future. If there is a default by the counterparty to a swap, the Trust will have contractual remedies pursuant to the swap agreement, but any recovery may be delayed depending on the circumstances of the default. To limit the counterparty risk involved in swap agreements, the Trust will only enter into swap agreements with counterparties that meet certain criteria. Although there can be no assurance that the Trust will be able to do so, the Trust may be able to reduce or eliminate its exposure under a swap agreement either by assignment or other disposition, or by entering into an offsetting swap agreement with the same party or another creditworthy party. The Trust may have limited ability to eliminate its exposure under a credit default swap if the credit of the referenced entity or underlying asset has declined.

The swaps market was largely unregulated prior to the enactment of federal legislation known as the Dodd-Frank Wall Street Reform and Consumer Protection Act (the “Dodd-Frank Act”), which was enacted in 2010 in response to turmoil in the financial markets and other market events. Among other things, the Dodd-Frank Act sets forth a new regulatory framework for certain OTC derivatives, such as swaps, in which the Trust may invest. The Dodd-Frank Act requires many swap transactions to be executed on registered exchanges or through swap execution facilities, cleared through a regulated clearinghouse, and publicly reported. In addition, many market participants are now regulated as swap dealers or major swap participants, and are, or will be, subject to certain minimum capital and margin requirements and business conduct standards. The statutory requirements of the Dodd-Frank Act are being implemented primarily through rules and regulations adopted by the SEC and/or the CFTC. There is a prescribed phase-in period during which most of the mandated rulemaking and regulations are being implemented, and temporary exemptions from certain rules and regulations have been granted so that current trading practices will not be unduly disrupted during the transition period.

Currently, central clearing is only required for certain market participants trading certain instruments, although central clearing for additional instruments is expected to be implemented by the CFTC until the majority of the swaps market is ultimately subject to central clearing. In addition, uncleared OTC swaps will be subject to regulatory collateral requirements that could adversely affect the Trust’s ability to enter into swaps in the OTC market. These developments could cause the Trust to terminate new or existing swap agreements or to realize amounts to be received under such instruments at an inopportune time. Until the mandated rulemaking and regulations are

Eaton Vance Senior Income Trust

SAI dated [_____], 2018

implemented completely, it will not be possible to determine the complete impact of the Dodd-Frank Act and related regulations on the Trust, and the establishment of a centralized exchange or market for swap transactions may not result in swaps being easier to value or trade. However, it is expected that swap dealers, major market participants, and swap counterparties will experience other new and/or additional regulations, requirements, compliance burdens, and associated costs. The legislation and rules yet to be promulgated and/or implemented may exert a negative effect on the Trust’s ability to meet its investment objective, either through limits or requirements imposed on the Trust or its counterparties. The swap market could be disrupted or limited as a result of the implementation of this legislation, and the new requirements may increase the cost of the Trust’s investments and of doing business, which could adversely affect the ability of the Trust to buy or sell OTC derivatives.

Swap agreements include (but are not limited to):

Credit Default Swaps. Under a credit default swap agreement, the protection “buyer” in a credit default contract is generally obligated to pay the protection “seller” an upfront or a periodic stream of payments over the term of the contract, provided that no credit event, such as a default, on a reference instrument has occurred. If a credit event occurs, the seller generally must pay the buyer the “par value” (full notional value) of the reference instrument in exchange for an equal face amount of the reference instrument described in the swap, or the seller may be required to deliver the related net cash amount, if the swap is cash settled. If the Trust is a buyer and no credit event occurs, the Trust may recover nothing if the swap is held through its termination date. As a seller, the Trust generally receives an upfront payment or a fixed rate of income throughout the term of the swap provided that there is no credit event. As the seller, the Trust would effectively add leverage to its portfolio because, in addition to its total net assets, the Trust would be subject to investment exposure on the notional amount of the swap. The determination of a credit event under the swap agreement will depend on the terms of the agreement and may rely on the decision of persons that are not a party to the agreement. The Trust’s obligations under a credit default swap agreement will be accrued daily (offset against any amounts owed to the Trust).

Total Return Swaps. Total return swap agreements are contracts in which one party agrees to make periodic payments to another party based on the change in market value of the assets underlying the contract, which may include a specified security, basket of securities or securities indices during the specified period, in return for periodic payments based on a fixed or variable interest rate or the total return from other underlying assets. Total return swap agreements may be used to obtain exposure to a security or market without owning or taking physical custody of such security or investing directly in such market. Total return swap agreements may effectively add leverage to the Trust’s portfolio because, in addition to its total net assets, the Trust would be subject to investment exposure on the notional amount of the swap. Generally, the Trust will enter into total return swaps on a net basis (i.e., the two payment streams are netted out, with the Trust receiving or paying, as the case may be, only the net amount of the two payments). The net amount of the excess, if any, of the Trust’s obligations over its entitlements with respect to each total return swap will be accrued on a daily basis. If the total return swap transaction is entered into on other than a net basis, the full amount of the Trust’s obligations will be accrued on a daily basis, and the full amount of the Trust’s obligations will be segregated by the Trust in an amount equal to or greater than the market value of the liabilities under the total return swap or the amount it would have cost the Trust initially to make an equivalent direct investment, plus or minus any amount the Trust is obligated to pay or is to receive under the total return swap agreement.

Interest Rate Swaps, Caps and Floors. Interest rate swaps are OTC contracts in which each party agrees to make a periodic interest payment based on an index or the value of an asset in return for a periodic payment from the other party based on a different index or asset. The purchase of an interest rate floor entitles the purchaser, to the extent that a specified index falls below a predetermined interest rate, to receive payments of interest on a notional principal amount from the party selling such interest rate floor. The purchase of an interest rate cap entitles the purchaser, to the extent that a specified index rises above a predetermined interest rate, to receive payments of interest on a notional principal amount from the party selling such interest rate cap. The Trust usually will enter into interest rate swap transactions on a net basis (i.e., the two payment streams are netted out, with the Trust receiving or paying, as the case may be, only the net amount of the two payments). The net amount of the excess, if any, of the Trust’s obligations over its entitlements with respect to each interest rate swap will be accrued on a daily basis. If the interest rate swap transaction is entered into on other than a net basis, the full amount of the Trust’s obligations will be accrued on a daily basis. Certain federal income tax requirements may limit the Trust’s ability to engage in certain interest rate transactions.

The regulation of derivatives has undergone substantial change in recent years and such change may continue. In particular, the Dodd-Frank Wall Street Reform and Consumer Protection Act (the “Dodd-Frank Act”), and regulations proposed to be promulgated thereunder require many derivatives to be cleared and traded on an exchange, expand entity registration requirements, impose business conduct requirements on dealers that enter into swaps with a pension plan, endowment, retirement plan or government entity, and require banks to move some derivatives trading

Eaton Vance Senior Income Trust

SAI dated [_____], 2018

units to a non-guaranteed affiliate separate from the deposit-taking bank or divest them altogether. Although the CFTC has released final rules relating to clearing, reporting, recordkeeping, required margin and registration requirements under the legislation, many of the provisions are subject to further final rule making, and thus its ultimate impact remains unclear. New regulations and the implementation of existing regulations could, among other things, restrict the Trust’s ability to engage in derivatives transactions (for example, by making certain types of derivatives transactions no longer available to the Trust) and/or increase the costs of such derivatives transactions (for example, by increasing margin or capital requirements), and the Trust may be unable to fully execute its investment strategies as a result. Limits or restrictions applicable to the counterparties with which the Trust engages in derivative transactions also could prevent the Trust from using these instruments or affect the pricing or other factors relating to these instruments, or may change the availability of certain investments.

Likewise, the SEC has proposed regulations that, if adopted, would significantly change the manner in which a Fund must segregate assets to cover its future obligations. The proposed regulations would restrict its ability to enter into derivative transactions for speculative or hedging purposes and would require the Trust’s Board to adopt a derivative risk management and governance framework. These regulations could also limit the ability of a Fund to use these instruments as part of its investment management strategy, increase the costs of using these instruments or make them less effective. Limits or restrictions applicable to the counterparties with which a Fund engages in derivative transactions also could prevent the Trust from using these instruments or affect the pricing or other factors relating to these instruments, or may change the availability of certain investments.

Legislation may be enacted that could negatively affect the assets of the Trust. Legislation or regulation may also change the way in which the Trust itself is regulated. The effects of any new governmental regulation cannot be predicted and there can be no assurance that any new governmental regulation will not adversely affect the Trust’s ability to achieve its investment objective(s).

Asset Coverage. To the extent required by SEC guidance, if a transaction creates a future obligation of the Trust to another party the Trust will: (1) cover the obligation by entering into an offsetting position or transaction; and/or (2) segregate cash and/or liquid securities with a value (together with any collateral posted with respect to the obligation) at least equal to the marked-to market value of the obligations. Assets used as cover or segregated cannot be sold while the position(s) requiring cover is open unless replaced with other appropriate assets. The types of transactions that may require asset coverage include (but are not limited to) reverse repurchase agreements, repurchase agreements, short sales, securities lending, forward contracts, certain options, forward commitments, futures contracts, when-issued securities, swap agreements, residual interest bonds, and participation in revolving credit facilities.

Securities Lending. As described in the Prospectus, the Trust may lend a portion of its portfolio Senior Loans or other securities to broker-dealers or other institutional borrowers. Loans will be made only to organizations whose credit quality or claims paying ability is considered by the Adviser to be at least investment grade. All securities loans will be collateralized on a continuous basis by cash or U.S. government securities having a value, marked to market daily, of at least 100% of the market value of the loaned securities. The Trust may receive loan fees in connection with loans that are collateralized by securities or on loans of securities for which there is special demand. The Trust may also seek to earn income on securities loans by reinvesting cash collateral in mortgage-backed securities (“MBS”) or other securities consistent with its investment objective and policies, seeking to invest at rates that are higher than the “rebate” rate that it normally will pay to the borrower with respect to such cash collateral. Any such reinvestment will be subject to the investment policies, restrictions and risk considerations described in the Prospectus and in this SAI.

Senior Loans and other securities may result in delays in recovering, or a failure of the borrower to return, the loaned securities. The defaulting borrower ordinarily would be liable to the Trust for any losses resulting from such delays or failures, and the collateral provided in connection with the loan normally would also be available for that purpose. Securities loans normally may be terminated by either the Trust or the borrower at any time. Upon termination and the return of the loaned securities, the Trust would be required to return the related cash or securities collateral to the borrower and it may be required to liquidate longer term portfolio securities in order to do so. To the extent that such securities have decreased in value, this may result in the Trust realizing a loss at a time when it would not otherwise do so. The Trust also may incur losses if it is unable to reinvest cash collateral at rates higher than applicable rebate rates paid to borrowers and related administrative costs. These risks are substantially the same as those incurred through investment leverage, and will be subject to the investment policies, restrictions and risk considerations described in the Prospectus and in this SAI.

The Trust will receive amounts equivalent to any interest or other distributions paid on securities while they are on loan, and the Trust will not be entitled to exercise voting or other beneficial rights on loaned securities. The Trust will exercise its right to terminate loans and thereby regain these rights whenever the Adviser considers it to be in the Trust’s interest to do so, taking into account the related loss of reinvestment income and other factors.

Eaton Vance Senior Income Trust

SAI dated [_____], 2018

Short-Term Trading. Securities may be sold in anticipation of market decline (a rise in interest rates) or purchased in anticipation of a market rise (a decline in interest rates) and later sold. In addition, a security may be sold and another purchased at approximately the same time to take advantage of what the Adviser believes to be a temporary disparity in the normal yield relationship between the two securities. Yield disparities may occur for reasons not directly related to the investment quality of particular issues or the general movement of interest rates, such as changes in the overall demand for or supply of various types of fixed-income securities or changes in the investment objectives of investors.

Cybersecurity Risk. With the increased use of technologies by Trust service providers to conduct business, such as the Internet, the Trust is susceptible to operational, information security and related risks. In general, cyber incidents can result from deliberate attacks or unintentional events. Cyber attacks include, but are not limited to, gaining unauthorized access to digital systems (e.g., through “hacking” or malicious software coding) for purposes of misappropriating assets or sensitive information, corrupting data, or causing operational disruption. Cyber attacks may also be carried out in a manner that does not require gaining unauthorized access, such as causing denial-of-service attacks on websites (i.e., efforts to make network services unavailable to intended users). Cybersecurity failures or breaches by the Trust’s investment adviser or administrator and other service providers (including, but not limited to, the custodian or transfer agent), and the issuers of securities in which the Trust invests, have the ability to cause disruptions and impact business operations potentially resulting in financial losses, interference with the Trust’s ability to calculate its net asset value, impediments to trading, violations of applicable privacy and other laws, regulatory fines, penalties, reputational damage, reimbursement or other compensation costs, or additional compliance costs. While various Trust service providers have established business continuity plans and risk management systems intended to identify and mitigate cyber attacks, there are inherent limitations in such plans and systems including the possibility that certain risks have not been identified. Furthermore, the Trust cannot control the cybersecurity plans and systems put in place by service providers to the Trust and issuers in which the Trust invests. The Trust and its shareholders could be negatively impacted as a result.

Operational Risk. The Trust’s service providers, including the investment adviser, may experience disruptions or operating errors that could negatively impact the Trust. While service providers are expected to have appropriate operational risk management policies and procedures, their methods of operational risk management may differ from the Trust’s in the setting of priorities, the personnel and resources available or the effectiveness of relevant controls. It also is not possible for Trust service providers to identify all of the operational risks that may affect the Trust or to develop processes and controls to completely eliminate or mitigate their occurrence or effects.

Temporary Investments. The Trust may invest temporarily in cash or cash equivalents. Cash equivalents are highly liquid, short-term securities such as commercial paper, time deposits, certificates of deposit, short-term notes and short-term U.S. Government obligations.

Investment Restrictions. The following investment restrictions of the Trust are designated as fundamental policies and as such cannot be changed without the approval of the holders of a majority of the Trust’s outstanding voting securities, which as used in this SAI means the lesser of (a) 67% of the shares of the Trust present or represented by proxy at a meeting if the holders of more than 50% of the outstanding shares are present or represented at the meeting or (b) more than 50% of outstanding shares of the Trust. As a matter of fundamental policy the Trust may not:

(1)

Borrow money, except as permitted by the Investment Company Act of 1940, as amended (the “1940 Act”). The 1940 Act currently requires that any indebtedness incurred by a closed-end investment company have an asset coverage of at least 300%;

(2)

Issue senior securities, as defined in the 1940 Act, other than (i) preferred shares which immediately after issuance will have asset coverage of at least 200%, (ii) indebtedness which immediately after issuance will have asset coverage of at least 300%, or (iii) the borrowings permitted by investment restriction (1) above. The 1940 Act currently defines “senior security” as any bond, debenture, note or similar obligation or instrument constituting a security and evidencing indebtedness, and any stock of a class having priority over any other class as to distribution of assets or payment of dividends. Debt and equity securities issued by a closed-end investment company meeting the foregoing asset coverage provisions are excluded from the general 1940 Act prohibition on the issuance of senior securities;

(3)

Purchase securities on margin (but the Trust may obtain such short-term credits as may be necessary for the clearance of purchases and sales of securities). The purchase of loan interests, securities or other investment assets with the proceeds of a permitted borrowing or securities offering will not be deemed to be the purchase of securities on margin;

(4)

Underwrite securities issued by other persons, except insofar as it may technically be deemed to be an underwriter under the Securities Act of 1933, as amended, in selling or disposing of a portfolio investment;

Eaton Vance Senior Income Trust

SAI dated [_____], 2018

(5)

Make loans to other persons, except by (a) the acquisition of loan interests, debt securities and other obligations in which the Trust is authorized to invest in accordance with its investment objective and policies, (b) entering into repurchase agreements, and (c) lending its portfolio securities;

(6)

Purchase any security if, as a result of such purchase, 25% or more of the Trust's total assets (taken at current value) would be invested in the securities of Borrowers and other issuers having their principal business activities in the same industry (the electric, gas, water and telephone utility industries, commercial banks, thrift institutions and finance companies being treated as separate industries for the purpose of this restriction); provided that there is no limitation with respect to obligations issued or guaranteed by the U.S. Government or any of its agencies or instrumentalities;

(7)

Purchase or sell real estate, although it may purchase and sell securities that are secured by interests in real estate and securities of issuers that invest or deal in real estate. The Trust reserves the freedom of action to hold and to sell real estate acquired as a result of the ownership of securities;

(8)

Purchase or sell physical commodities or contracts for the purchase or sale of physical commodities. Physical commodities do not include futures contracts with respect to securities, securities indices or other financial instruments; and

(9)

With respect to 75% of its total assets, invest more than 5% of its total assets in the securities of a single issuer or purchase more than 10% of the outstanding voting securities of a single issuer, except obligations issued or guaranteed by the U.S. government, its agencies or instrumentalities and except securities of other investment companies.

The Trust may borrow money as a temporary measure for extraordinary or emergency purposes, including the payment of dividends and the settlement of securities transactions which otherwise might require untimely dispositions of Trust securities. The 1940 Act currently requires that the Trust have 300% asset coverage with respect to all borrowings other than temporary borrowings.

For the purpose of investment restriction (6), the Trust will consider all relevant factors in determining who is the issuer of the loan interest, including: the credit quality of the Borrower, the amount and quality of the collateral, the terms of the Loan Agreement and other relevant agreements (including inter-creditor agreements), the degree to which the credit of such interpositioned person was deemed material to the decision to purchase the Senior Loan, the interest rate environment, and general economic conditions applicable to the Borrower and such interpositioned person.

For purposes of construing restriction (9), securities of the U.S. Government, its agencies, or instrumentalities are not considered to represent industries. Municipal obligations backed by the credit of a governmental entity are also not considered to represent industries.

The Trust has adopted the following nonfundamental investment policy, which may be changed by the Board without approval of the Trust’s shareholders. As a matter of nonfundamental policy, the Trust may not make short sales of securities or maintain a short position, unless at all times when a short position is open it either owns an equal amount of such securities or owns securities convertible into or exchangeable, without payment of any further consideration, for securities of the same issuer as, and equal in amount to, the securities sold short.

The Trust may invest more than 10% of its total assets in one or more other management investment companies (or may invest in affiliated investment companies) to the extent permitted by the 1940 Act and rules thereunder.

Whenever an investment policy or investment restriction set forth in the Prospectus or this SAI states a requirement with respect to the percentage of assets that may be invested in any security or other asset, or describes a policy regarding quality standards, such percentage limitation or standard shall be determined immediately after and as a result of the acquisition by the Trust of such security or asset. Accordingly, unless otherwise noted, any later increase or decrease resulting from a change in values, assets or other circumstances or any subsequent rating change made by a rating service (or as determined by the Adviser if the security is not rated by a rating agency) will not compel the Trust to dispose of such security or other asset. Notwithstanding the foregoing, the Trust must always be in compliance with the borrowing policies set forth above.

Eaton Vance Senior Income Trust

SAI dated [_____], 2018

TRUSTEES AND OFFICERS

The Board of Trustees of the Trust (the “Board”) is responsible for the overall management and supervision of the affairs of the Trust. The Board members and officers of the Trust are listed below. Except as indicated, each individual has held the office shown or other offices in the same company for the last five years. The “noninterested Trustees” consist of those Trustees who are not “interested persons” of the Trust, as that term is defined under the 1940 Act. The business address of each Board member and officer is Two International Place, Boston, Massachusetts 02110. As used in this SAI, “EVC” refers to Eaton Vance Corp., “EV” refers to Eaton Vance, Inc., “BMR” refers to Boston Management and Research and “EVD” refers to Eaton Vance Distributors Inc. EVC and EV are the corporate parent and trustee, respectively, of Eaton Vance and BMR. EVD is a wholly-owned subsidiary of EVC. Each officer affiliated with Eaton Vance may hold a position with other Eaton Vance affiliates that is comparable to his or her position with Eaton Vance listed below.

Name and Year of Birth	Trust Position(s)⁽¹⁾	Length of Service	Principal Occupation(s) During Past Five Years and Other Relevant Experience	Number of Portfolios in Fund Complex Overseen By Trustee⁽²⁾	Other Directorships Held During Last Five Years⁽³⁾
Interested Trustee
THOMAS E. FAUST JR. 1958	Class I Trustee	Until 2020. 3 years. Since 2007.	Chairman, Chief Executive Officer and President of EVC, Director and President of EV, Chief Executive Officer and President of Eaton Vance and BMR, and Director of EVD. Trustee and/or officer of 174 registered investment companies. Mr. Faust is an interested person because of his positions with BMR, Eaton Vance, EVC, EVD and EV, which are affiliates of the Trust.	174	Director of EVC and Hexavest Inc. (investment management firm).
Noninterested Trustees
MARK R. FETTING 1954	Class II Trustee	Until 2021. 3 years. Since 2016.	Private investor. Formerly held various positions at Legg Mason, Inc. (investment management firm) (2000-2012), including President, Chief Executive Officer, Director and Chairman (2008-2012), Senior Executive Vice President (2004-2008) and Executive Vice President (2001-2004). Formerly, President of Legg Mason family of funds (2001-2008). Formerly, Division President and Senior Officer of Prudential Financial Group, Inc. and related companies (investment management firm) (1991-2000).	174	None
CYNTHIA E. FROST 1961	Class I Trustee	Until 2020. 3 years. Since 2014.	Private investor. Formerly, Chief Investment Officer of Brown University (university endowment) (2000-2012). Formerly, Portfolio Strategist for Duke Management Company (university endowment manager) (1995-2000). Formerly, Managing Director, Cambridge Associates (investment consulting company) (1989-1995). Formerly, Consultant, Bain and Company (management consulting firm) (1987-1989). Formerly, Senior Equity Analyst, BA Investment Management Company (1983-1985).	174	None

Eaton Vance Senior Income Trust

SAI dated [_____], 2018

Name and Year of Birth	Trust Position(s)⁽¹⁾	Length of Service	Principal Occupation(s) During Past Five Years and Other Relevant Experience	Number of Portfolios in Fund Complex Overseen By Trustee⁽²⁾	Other Directorships Held During Last Five Years⁽³⁾
GEORGE J. GORMAN 1952	Class III Trustee	Until 2019. 3 years. Since 2014.	Principal at George J. Gorman LLC (consulting firm). Formerly, Senior Partner at Ernst & Young LLP (a registered public accounting firm) (1974-2009).	174	Formerly, Trustee of the BofA Funds Series Trust (11 funds) (2011-2014) and of the Ashmore Funds (9 funds) (2010-2014).
VALERIE A. MOSLEY 1960	Class I Trustee⁽⁴⁾	Until 2020. 3 years. Since 2014.	Chairwoman and Chief Executive Officer of Valmo Ventures (a consulting and investment firm). Former Partner and Senior Vice President, Portfolio Manager and Investment Strategist at Wellington Management Company, LLP (investment management firm) (1992-2012). Former Chief Investment Officer, PG Corbin Asset Management (1990-1992). Formerly worked in institutional corporate bond sales at Kidder Peabody (1986-1990).	174	Director of Dynex Capital, Inc. (mortgage REIT) (since 2013).
WILLIAM H. PARK 1947	Chairperson of the Board and Class III Trustee⁽⁴⁾	Until 2019. 3 years. Chairperson of the Board since 2016 and Trustee since 2003.	Private investor. Formerly, Consultant (management and transactional) (2012-2014). Formerly, Chief Financial Officer, Aveon Group, L.P. (investment management firm) (2010-2011). Formerly, Vice Chairman, Commercial Industrial Finance Corp. (specialty finance company) (2006-2010). Formerly, President and Chief Executive Officer, Prizm Capital Management, LLC (investment management firm) (2002-2005). Formerly, Executive Vice President and Chief Financial Officer, United Asset Management Corporation (investment management firm) (1982-2001). Formerly, Senior Manager, Price Waterhouse (now PricewaterhouseCoopers) (a registered public accounting firm) (1972-1981).	174	None
HELEN FRAME PETERS 1948	Class II Trustee	Until 2021. 3 years. Since 2008.	Professor of Finance, Carroll School of Management, Boston College. Formerly, Dean, Carroll School of Management, Boston College (2000-2002). Formerly, Chief Investment Officer, Fixed Income, Scudder Kemper Investments (investment management firm) (1998-1999). Formerly, Chief Investment Officer, Equity and Fixed Income, Colonial Management Associates (investment management firm) (1991-1998).	174	None
KEITH QUINTON 1958	Class II Trustee	Until 2021. 3 years. Since 2018.	Independent Investment Committee Member at New Hampshire Retirement System (since 2017). Advisory Committee member at Northfield Information Services, Inc. (risk management analytics provider) (since 2016). Formerly, Portfolio Manager and Senior Quantitative Analyst at Fidelity Investments (investment management firm) (2001-2014).	174	Director of New Hampshire Municipal Bond Bank (since 2016).

Eaton Vance Senior Income Trust

SAI dated [_____], 2018

Name and Year of Birth	Trust Position(s)⁽¹⁾	Length of Service	Principal Occupation(s) During Past Five Years and Other Relevant Experience	Number of Portfolios in Fund Complex Overseen By Trustee⁽²⁾	Other Directorships Held During Last Five Years⁽³⁾
MARCUS L. SMITH 1966	Class III Trustee	Until 2019. 1 year. Since 2018.	Member of Posse Boston Advisory Board (foundation) (since 2015); Trustee at University of Mount Union (since 2008). Formerly, Portfolio Manager at MFS Investment Management (investment management firm) (1994-2017).	174	Director of MSCI Inc. (global provider of investment decision support tools) (since 2017). Director of DCT Industrial Trust Inc. (logistics real estate company) (since 2017).
SUSAN J. SUTHERLAND 1957	Class I Trustee	Until 2020. 3 years. Since 2015.	Private investor. Formerly, Associate, Counsel and Partner at Skadden, Arps, Slate, Meagher & Flom LLP (law firm) (1982-2013).	174	Formerly, Director of Montpelier Re Holdings Ltd. (global provider of customized insurance and reinsurance products) (2013-2015).
HARRIETT TEE TAGGART 1948	Class III Trustee	Until 2019. 3 years. Since 2011.	Managing Director, Taggart Associates (a professional practice firm). Formerly, Partner and Senior Vice President, Wellington Management Company, LLP (investment management firm) (1983-2006). Ms. Taggart has apprised the Board of Trustees that she intends to retire as a Trustee of all Eaton Vance Funds effective December 31, 2018.	174	Director of Albemarle Corporation (chemicals manufacturer) (since 2007) and The Hanover Group (specialty property and casualty insurance company) (since 2009).
SCOTT E. WENNERHOLM 1959	Class II Trustee	Until 2021. 3 years. Since 2016.	Formerly, Trustee at Wheelock College (postsecondary institution) (2012-2018). Formerly, Consultant at GF Parish Group (executive recruiting firm) (2016-2017). Formerly, Chief Operating Officer and Executive Vice President at BNY Mellon Asset Management (investment management firm) (2005-2011). Formerly, Chief Operating Officer and Chief Financial Officer at Natixis Global Asset Management (investment management firm) (1997-2004). Formerly, Vice President at Fidelity Investments Institutional Services (investment management firm) (1994-1997).	174	None

⁽¹⁾

The Board of Trustees is divided into three classes, each class having a term of three years to expire on the date of the third annual meeting following its election.

⁽²⁾

Includes both master and feeder funds in a master-feeder structure.

⁽³⁾

During their respective tenures, the Trustees (except for Mmes. Frost and Sutherland and Messrs. Fetting, Gorman, Quinton, Smith and Wennerholm) also served as Board members of one or more of the following funds (which operated in the years noted): eUnits^TM 2 Year U.S. Market Participation Trust: Upside to Cap/Buffered Downside (launched in 2012 and terminated in 2014); and eUnits^TM 2 Year U.S. Market Participation Trust II: Upside to Cap/Buffered Downside (launched in 2012 and terminated in 2014). However, Ms. Mosley did not serve as a Board member of eUnits^TM 2 Year U.S. Market Participation Trust: Upside to Cap/Buffered Downside (launched in 2012 and terminated in 2014).

⁽⁴⁾

APS Trustee.

Eaton Vance Senior Income Trust

SAI dated [_____], 2018

Principal Officers who are not Trustees
Name and Year of Birth	Trust Position(s)	Length of Service	Principal Occupation(s) During Past Five Years
PAYSON F. SWAFFIELD 1956	President	Since 2017	Vice President and Chief Income Investment Officer of Eaton Vance and BMR. Officer of 146 registered investment companies managed by Eaton Vance or BMR. Also Vice President of Calvert Research Management (“CRM”) since 2016.
MAUREEN A. GEMMA 1960	Vice President, Secretary and Chief Legal Officer	Vice President since 2011, Secretary since 2007 and Chief Legal Officer since 2008	Vice President of Eaton Vance and BMR. Officer of 174 registered investment companies managed by Eaton Vance or BMR. Also Vice President of CRM and officer of 39 registered investment companies advised or administered by CRM since 2016.
JAMES F. KIRCHNER 1967	Treasurer	Since 2013	Vice President of Eaton Vance and BMR. Officer of 174 registered investment companies managed by Eaton Vance or BMR. Also Vice President of CRM and officer of 39 registered investment companies advised or administered by CRM since 2016.
RICHARD F. FROIO 1968	Chief Compliance Officer	Since 2017	Vice President of Eaton Vance and BMR since 2017. Officer of 174 registered investment companies managed by Eaton Vance or BMR. Formerly, Deputy Chief Compliance Officer (Adviser/Funds) and Chief Compliance Officer (Distribution) at PIMCO (2012-2017) and Managing Director at BlackRock/Barclays Global Investors (2009-2012).

The Board has general oversight responsibility with respect to the business and affairs of the Trust. The Board has engaged an investment adviser and (if applicable) a sub-adviser(s) (collectively the “adviser”) to manage the Trust and an administrator to administer the Trust and is responsible for overseeing such adviser and administrator and other service providers to the Trust. The Board is currently composed of twelve Trustees, including eleven Trustees who are not “interested persons” of the Trust, as that term is defined in the 1940 Act (each a “noninterested Trustee”). In addition to six regularly scheduled meetings per year, the Board holds special meetings or informal conference calls to discuss specific matters that may require action prior to the next regular meeting. As discussed below, the Board has established six committees to assist the Board in performing its oversight responsibilities.

The Board has appointed a noninterested Trustee to serve in the role of Chairperson. The Chairperson’s primary role is to participate in the preparation of the agenda for meetings of the Board and the identification of information to be presented to the Board with respect to matters to be acted upon by the Board. The Chairperson also presides at all meetings of the Board and acts as a liaison with service providers, officers, attorneys, and other Board members generally between meetings. The Chairperson may perform such other functions as may be requested by the Board from time to time. In addition, the Board may appoint a noninterested Trustee to serve in the role of Vice-Chairperson. The Vice-Chairperson has the power and authority to perform any or all of the duties and responsibilities of the Chairperson in the absence of the Chairperson and/or as requested by the Chairperson. Except for any duties specified herein or pursuant to the Trust’s Declaration of Trust or By-laws, the designation of Chairperson or Vice-Chairperson does not impose on such noninterested Trustee any duties, obligations or liability that is greater than the duties, obligations or liability imposed on such person as a member of the Board, generally.

The Trust is subject to a number of risks, including, among others, investment, compliance, operational, and valuation risks. Risk oversight is part of the Board’s general oversight of the Trust and is addressed as part of various activities of the Board and its Committees. As part of its oversight of the Trust, the Board directly, or through a Committee, relies on and reviews reports from, among others, Trust management, the adviser, the administrator, the principal underwriter, the Chief Compliance Officer (the “CCO”), and other Trust service providers responsible for day-to-day oversight of Trust investments, operations and compliance to assist the Board in identifying and understanding the nature and extent of risks and determining whether, and to what extent, such risks can or should be mitigated. The Board also interacts with the CCO and with senior personnel of the adviser, administrator, principal underwriter and other Trust service providers and provides input on risk management issues during meetings of the Board and its Committees. Each of the adviser, administrator, principal underwriter and the other Trust service providers has its own, independent interest and responsibilities in risk management, and its policies and methods for carrying out risk management functions will depend, in part, on its individual priorities, resources and controls. It is not possible to identify all of the risks that may affect the Trust or to develop processes and controls to eliminate or mitigate their occurrence or effects. Moreover, it is necessary to bear certain risks (such as investment-related risks) to achieve the Trust’s goals.

Eaton Vance Senior Income Trust

SAI dated [_____], 2018

The Board, with the assistance of management and with input from the Board's various committees, reviews investment policies and risks in connection with its review of Trust performance. The Board has appointed a Trust CCO who oversees the implementation and testing of the Trust compliance program and reports to the Board regarding compliance matters for the Trust and its principal service providers. In addition, as part of the Board’s periodic review of the advisory, subadvisory (if applicable), distribution and other service provider agreements, the Board may consider risk management aspects of their operations and the functions for which they are responsible. With respect to valuation, the Board approves and periodically reviews valuation policies and procedures applicable to valuing the Trust’s shares. The administrator, the investment adviser and the sub-adviser (if applicable) are responsible for the implementation and day-to-day administration of these valuation policies and procedures and provides reports to the Audit Committee of the Board and the Board regarding these and related matters. In addition, the Audit Committee of the Board or the Board receives reports periodically from the independent public accounting firm for the Trust regarding tests performed by such firm on the valuation of all securities, as well as with respect to other risks associated with mutual funds. Reports received from service providers, legal counsel and the independent public accounting firm assist the Board in performing its oversight function.

The Trust’s Declaration of Trust does not set forth any specific qualifications to serve as a Trustee. The Charter of the Governance Committee also does not set forth any specific qualifications, but does set forth certain factors that the Committee may take into account in considering noninterested Trustee candidates. In general, no one factor is decisive in the selection of an individual to join the Board. Among the factors the Board considers when concluding that an individual should serve on the Board are the following: (i) knowledge in matters relating to the mutual fund industry; (ii) experience as a director or senior officer of public companies; (iii) educational background; (iv) reputation for high ethical standards and professional integrity; (v) specific financial, technical or other expertise, and the extent to which such expertise would complement the Board members’ existing mix of skills, core competencies and qualifications; (vi) perceived ability to contribute to the ongoing functions of the Board, including the ability and commitment to attend meetings regularly and work collaboratively with other members of the Board; (vii) the ability to qualify as a noninterested Trustee for purposes of the 1940 Act and any other actual or potential conflicts of interest involving the individual and the Trust; and (viii) such other factors as the Board determines to be relevant in light of the existing composition of the Board.

Among the attributes or skills common to all Board members are their ability to review critically, evaluate, question and discuss information provided to them, to interact effectively with the other members of the Board, management, sub-advisers, other service providers, counsel and independent registered public accounting firms, and to exercise effective and independent business judgment in the performance of their duties as members of the Board. Each Board member’s ability to perform his or her duties effectively has been attained through the Board member’s business, consulting, public service and/or academic positions and through experience from service as a member of the Boards of the Eaton Vance family of funds (“Eaton Vance Fund Boards”) (and/or in other capacities, including for any predecessor funds), public companies, or non-profit entities or other organizations as set forth below. Each Board member’s ability to perform his or her duties effectively also has been enhanced by his or her educational background, professional training, and/or other life experiences.

In respect of each current member of the Board, the individual’s substantial professional accomplishments and experience, including in fields related to the operations of registered investment companies, were a significant factor in the determination that the individual should serve as a member of the Board. The following is a summary of each Board member’s particular professional experience and additional considerations that contributed to the Board’s conclusion that he or she should serve as a member of the Board:

Thomas E. Faust Jr. Mr. Faust has served as a member of the Eaton Vance Fund Boards since 2007. He is currently Chairman, Chief Executive Officer and President of EVC, Director and President of EV, Chief Executive Officer and President of Eaton Vance and BMR, and Director of EVD. Mr. Faust has served as a Director of Hexavest Inc. since 2012 and of SigFig Wealth Management LLC since 2016. Mr. Faust previously served as an equity analyst, portfolio manager, Director of Equity Research and Management and Chief Investment Officer of Eaton Vance from 1985-2007. He holds B.S. degrees in Mechanical Engineering and Economics from the Massachusetts Institute of Technology and an MBA from Harvard Business School. Mr. Faust has been a Chartered Financial Analyst since 1988.

Mark R. Fetting. Mr. Fetting has served as a member of the Eaton Vance Fund Boards since 2016. He has over 30 years of experience in the investment management industry as an executive and in various leadership roles. From 2000 through 2012, Mr. Fetting served in several capacities at Legg Mason, Inc., including most recently serving as President, Chief Executive Officer, Director and Chairman from 2008 to his retirement in 2012. He also served as a Director/Trustee and Chairman of the Legg Mason family of funds from 2008-2012 and Director/Trustee of the Royce family of funds from 2001-2012. From 2001 through 2008, Mr. Fetting also served as President of the Legg Mason family of funds. From 1991 through 2000, Mr. Fetting served as Division President and Senior Officer of Prudential Financial Group, Inc. and related companies. Early in his professional career, Mr. Fetting was a Vice President at T. Rowe Price and served in leadership roles within the firm’s mutual fund division from 1981-1987.

Eaton Vance Senior Income Trust

SAI dated [_____], 2018

Cynthia E. Frost. Ms. Frost has served as a member of the Eaton Vance Fund Boards since 2014 and is the Chairperson of the Portfolio Management Committee. From 2000 through 2012, Ms. Frost was the Chief Investment Officer of Brown University, where she oversaw the evaluation, selection and monitoring of the third party investment managers who managed the university’s endowment. From 1995 through 2000, Ms. Frost was a Portfolio Strategist for Duke Management Company, which oversaw Duke University’s endowment. Ms. Frost also served in various investment and consulting roles at Cambridge Associates from 1989-1995, Bain and Company from 1987-1989 and BA Investment Management Company from 1983-1985. She serves as a member of an advisory board of Creciente Partners Investment Management, LLC, a manager of a hedge fund of funds, and has additional experience as a member of the investment committee of several non-profit organizations.

George J. Gorman. Mr. Gorman has served as a member of the Eaton Vance Fund Boards since 2014 and is the Chairperson of the Audit Committee. From 1974 through 2009, Mr. Gorman served in various capacities at Ernst & Young LLP, including as a Senior Partner in the Asset Management Group (from 1988) specializing in managing engagement teams responsible for auditing mutual funds registered with the SEC, hedge funds and private equity funds. Mr. Gorman also has experience serving as an independent trustee of other mutual fund complexes, including the Bank of America Money Market Funds Series Trust from 2011-2014 and the Ashmore Funds from 2010-2014.

Valerie A. Mosley. Ms. Mosley has served as a member of the Eaton Vance Fund Boards since 2014 and is the Chairperson of the Governance Committee and of the Ad Hoc Committee for Closed-End Fund Matters. She currently owns and manages a consulting and investment firm, Valmo Ventures and is a Director of Progress Investment Management Company, a manager of emerging managers. From 1992 through 2012, Ms. Mosley served in several capacities at Wellington Management Company, LLP, an investment management firm, including as a Partner, Senior Vice President, Portfolio Manager and Investment Strategist. Ms. Mosley also served as Chief Investment Officer at PG Corbin Asset Management from 1990-1992 and worked in institutional corporate bond sales at Kidder Peabody from 1986-1990. Ms. Mosley is a Director of Dynex Capital, Inc., a mortgage REIT, where she serves on the board’s audit and investment committees. She also serves as a trustee or board member of several major non-profit organizations and endowments, including New Profit, a non-profit venture philanthropy fund. She is a member of the Risk Audit Committee of the United Auto Workers Retiree Medical Benefits Trust and a member of the Investment Advisory Committee of New York State Common Retirement Fund. She is also an advisor to New Technology Ventures, a venture capital firm.

William H. Park. Mr. Park has served as a member of the Eaton Vance Fund Boards since 2003 and is the Independent Chairperson of the Board. Mr. Park was formerly a consultant from 2012-2014 and formerly the Chief Financial Officer of Aveon Group, L.P. from 2010-2011. Mr. Park also served as Vice Chairman of Commercial Industrial Finance Corp. from 2006-2010, as President and Chief Executive Officer of Prizm Capital Management, LLC from 2002-2005, as Executive Vice President and Chief Financial Officer of United Asset Management Corporation from 1982-2001 and as Senior Manager of Price Waterhouse (now PricewaterhouseCoopers) from 1972-1981.

Helen Frame Peters. Dr. Peters has served as a member of the Eaton Vance Fund Boards since 2008. Dr. Peters is currently a Professor of Finance at Carroll School of Management, Boston College and was formerly Dean of Carroll School of Management from 2000-2002. Dr. Peters was previously a Director of BJ’s Wholesale Club, Inc. from 2004-2011. In addition, Dr. Peters was the Chief Investment Officer, Fixed Income at Scudder Kemper Investments from 1998-1999 and Chief Investment Officer, Equity and Fixed Income at Colonial Management Associates from 1991-1998. Dr. Peters also served as a Trustee of SPDR Index Shares Funds and SPDR Series Trust from 2000-2009 and as a Director of the Federal Home Loan Bank of Boston from 2007-2009.

Keith Quinton. Mr. Quinton has served as a member of the Eaton Vance Fund Boards since October 1, 2018. He had over thirty years of experience in the investment industry before retiring from Fidelity Investments in 2014. Prior to joining Fidelity, Mr. Quinton was a vice president and quantitative analyst at MFS Investment Management from 2000-2001. From 1997 through 2000, he was a senior quantitative analyst at Santander Global Advisors and, from 1995 through 1997, Mr. Quinton was senior vice president in the quantitative equity research department at Putnam Investments. Prior to joining Putnam Investments, Mr. Quinton served in various investment roles at Eberstadt Fleming, Falconwood Securities Corporation and Burnham Lambert, where he began his career in the investment industry as a senior quantitative analyst in 1983. Mr. Quinton currently serves as an Independent Investment Committee Member of the New Hampshire Retirement System, a five member committee that manages investments based on the investment policy and asset allocation approved by the board of trustees, and as a Director of the New Hampshire Municipal Bond Bank.

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Marcus L. Smith. Mr. Smith has served as a member of the Eaton Vance Fund Boards since October 1, 2018. Since 2017, Mr. Smith has been a Director of MSCI Inc., a leading provider of investment decision support tools worldwide, where he serves on the Audit Committee, and a Director of DCT Industrial Trust Inc., a leading logistics real estate company, where he is a member of the Nominating and Corporate Governance and Audit Committees. From 1994 through 2017, Mr. Smith served in several capacities at MFS Investment Management, an investment management firm, where he managed the MFS Institutional International Fund for 17 years and the MFS Concentrated International Fund for 10 years. In addition to his portfolio management duties, Mr. Smith served as Director of Equity, Canada from 2012-2017, Director of Equity, Asia from 2010-2012, and Director of Asian Equity Research from 2005-2010. Prior to joining MFS, Mr. Smith was a senior consultant at Andersen Consulting (now known as Accenture) from 1988-1992. Mr. Smith served as a United States Army Reserve Officer from 1987-1992. He has also been a trustee of the University of Mount Union since 2008 and has served as the chairman of the finance committee since 2015. Mr. Smith currently sits on the Boston advisory board of the Posse Foundation.

Susan J. Sutherland. Ms. Sutherland has served as a member of the Eaton Vance Fund Boards since 2015 and is the Chairperson of the Compliance Reports and Regulatory Matters Committee. She is also a Director of Ascot Group Limited which, through its related businesses including Syndicate 1414 at Lloyd’s of London, is a leading global underwriter of specialty property and casualty insurance and reinsurance. Ms. Sutherland was a Director of Montpelier Re Holdings Ltd., a global provider of customized reinsurance and insurance products, from 2013 until its sale in 2015 and of Hagerty Holding Corp., a leading provider of specialized automobile and marine insurance from 2015-2018. From 1982 through 2013, Ms. Sutherland was an associate, counsel and then a partner in the Financial Institutions Group of Skadden, Arps, Slate, Meagher & Flom LLP, where she primarily represented U.S. and international insurance and reinsurance companies, investment banks and private equity firms in insurance-related corporate transactions. In addition, Ms. Sutherland is qualified as a Governance Fellow of the National Association of Corporate Directors and has also served as a board member of prominent non-profit organizations.

Harriett Tee Taggart. Ms. Taggart has served as a member of the Eaton Vance Fund Boards since 2011. Ms. Taggart currently manages a professional practice, Taggart Associates. Since 2007, Ms. Taggart has been a Director of Albemarle Corporation, a specialty chemical company where she serves as a member of the Executive Compensation Committee. Since 2009 she has served as a Director of the Hanover Insurance Group, Inc. where she serves as Chair of the Nomination and Governance Committee. Ms. Taggart is also a trustee or member of several major non-profit boards, advisory committees and endowment investment companies. From 1983 through 2006, Ms. Taggart served in several capacities at Wellington Management Company, LLP, an investment management firm, including as a Partner, Senior Vice President and chemical industry sector portfolio manager. Ms. Taggart also served as a Director of the Lubrizol Corporation, a specialty chemicals manufacturer from 2007-2011.

Scott E. Wennerholm. Mr. Wennerholm has served as a member of the Eaton Vance Fund Boards since 2016 and is the Chairperson of the Contract Review Committee. He has over 30 years of experience in the financial services industry in various leadership and executive roles. Mr. Wennerholm served as Chief Operating Officer and Executive Vice President at BNY Mellon Asset Management from 2005-2011. He also served as Chief Operating Officer and Chief Financial Officer at Natixis Global Asset Management from 1997-2004 and was a Vice President at Fidelity Investments Institutional Services from 1994-1997. In addition, Mr. Wennerholm served as a Trustee at Wheelock College, a postsecondary institution from 2012-2018.

The Board(s) of the Trust has several standing Committees, including the Governance Committee, the Audit Committee, the Portfolio Management Committee, the Compliance Reports and Regulatory Matters Committee, the Contract Review Committee and the Ad Hoc Committee for Closed-End Fund Matters. Each of the Committees are comprised of only noninterested Trustees.

Mmes. Mosley (Chairperson), Frost, Peters, Sutherland and Taggart, and Messrs. Fetting, Gorman, Park, Quinton, Smith and Wennerholm are members of the Governance Committee. The purpose of the Governance Committee is to consider, evaluate and make recommendations to the Board with respect to the structure, membership and operation of the Board and the Committees thereof, including the nomination and selection of noninterested Trustees and a Chairperson of the Board and the compensation of such persons. During the fiscal year ended June 30, 2018, the Governance Committee convened seven times.

The Governance Committee will, when a vacancy exists, consider a nominee for Trustee recommended by a shareholder, provided that such recommendation is submitted in writing to the Trust’s Secretary at the principal executive office of the Trust. Such recommendations must be accompanied by biographical and occupational data on the candidate (including whether the candidate would be an “interested person” of the Trust), a written consent by the candidate to be named as a nominee and to serve as Trustee if elected, record and ownership information for the recommending shareholder with respect to the Trust, and a description of any arrangements or understandings regarding recommendation of the candidate for consideration.

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Messrs. Gorman (Chairperson), Park and Wennerholm and Ms. Mosley are members of the Audit Committee. The Board has designated Messrs. Gorman and Park, each a noninterested Trustee, as audit committee financial experts. The Audit Committee’s purposes are to (i) oversee the Trust's accounting and financial reporting processes, its internal control over financial reporting, and, as appropriate, the internal control over financial reporting of certain service providers; (ii) oversee or, as appropriate, assist Board oversight of the quality and integrity of the Trust's financial statements and the independent audit thereof; (iii) oversee, or, as appropriate, assist Board oversight of, the Trust's compliance with legal and regulatory requirements that relate to the Trust's accounting and financial reporting, internal control over financial reporting and independent audits; (iv) approve prior to appointment the engagement and, when appropriate, replacement of the independent registered public accounting firm, and, if applicable, nominate the independent registered public accounting firm to be proposed for shareholder ratification in any proxy statement of the Trust; (v) evaluate the qualifications, independence and performance of the independent registered public accounting firm and the audit partner in charge of leading the audit; and (vi) prepare, as necessary, audit committee reports consistent with the requirements of applicable SEC and stock exchange rules for inclusion in the proxy statement of the Trust. During the fiscal year ended June 30, 2018, the Audit Committee convened fourteen times.

Messrs. Wennerholm (Chairperson), Fetting, Gorman, Park, Quinton and Smith, and Mmes. Frost, Mosley, Peters, Sutherland and Taggart are members of the Contract Review Committee. The purposes of the Contract Review Committee are to consider, evaluate and make recommendations to the Board concerning the following matters: (i) contractual arrangements with each service provider to the Trust, including advisory, sub-advisory, transfer agency, custodial and fund accounting, distribution services and administrative services; (ii) any and all other matters in which any service provider (including Eaton Vance or any affiliated entity thereof) has an actual or potential conflict of interest with the interests of the Trust; and (iii) any other matter appropriate for review by the noninterested Trustees, unless the matter is within the responsibilities of the other Committees of the Board. During the fiscal year ended June 30, 2018, the Contract Review Committee convened eight times.

Mmes. Frost (Chairperson), Mosley and Peters and Messrs. Fetting and Smith are members of the Portfolio Management Committee. The purposes of the Portfolio Management Committee are to: (i) assist the Board in its oversight of the portfolio management process employed by the Trust and its investment adviser and sub-adviser(s), if applicable, relative to the Trust's stated objective(s), strategies and restrictions; (ii) assist the Board in its oversight of the trading policies and procedures and risk management techniques applicable to the Trust; and (iii) assist the Board in its monitoring of the performance results of all funds and portfolios, giving special attention to the performance of certain funds and portfolios that it or the Board identifies from time to time. During the fiscal year ended June 30, 2018, the Portfolio Management Committee convened eight times.

Mmes. Sutherland (Chairperson) and Taggart and Messrs. Gorman, Quinton and Wennerholm are members of the Compliance Reports and Regulatory Matters Committee. The purposes of the Compliance Reports and Regulatory Matters Committee are to: (i) assist the Board in its oversight role with respect to compliance issues and certain other regulatory matters affecting the Trust; (ii) serve as a liaison between the Board and the Trust's CCO; and (iii) serve as a “qualified legal compliance committee” within the rules promulgated by the SEC. During the fiscal year ended June 30, 2018, the Compliance Reports and Regulatory Matters Committee convened nine times.

Ms. Mosley (Chairperson) and Messrs. Gorman and Park are members of the Ad Hoc Committee for Closed-End Fund Matters. The purpose of the Ad Hoc Committee for Closed-End Fund Matters is to consider, evaluate and make recommendations to the Board with respect to issues specifically related to Eaton Vance Closed-End Funds. During the fiscal year ended June 30, 2018, the Ad Hoc Committee for Closed-End Fund Matters did not meet.

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Share Ownership. The following table shows the dollar range of equity securities beneficially owned by each Trustee in the Trust and in the Eaton Vance family of funds overseen by the Trustee as of December 31, 2017.

Name of Trustee	Dollar Range of Equity Securities Beneficially Owned in the Trust	Aggregate Dollar Range of Equity Securities Beneficially Owned in Funds Overseen by Trustee in the Eaton Vance Family of Funds
Interested Trustee
Thomas E. Faust Jr.	None	Over $100,000
Noninterested Trustees
Mark R. Fetting	None	Over $100,000
Cynthia E. Frost	None	Over $100,000
George J. Gorman	None	Over $100,000
Valerie A. Mosley	None	Over $100,000
William H. Park	None	Over $100,000
Helen Frame Peters	None	Over $100,000
Keith Quinton⁽¹⁾	None	None
Marcus L. Smith⁽¹⁾	None	Over $100,000
Susan J. Sutherland	None	Over $100,000⁽²⁾
Harriett Tee Taggart	None	Over $100,000
Scott E. Wennerholm	None	Over $100,000
⁽¹⁾ Messrs. Quinton and Smith began serving as Trustees effective October 1, 2018.
⁽²⁾ Includes shares which may be deemed to be beneficially owned through the Trustee Deferred Compensation Plan.

As of December 31, 2017, no noninterested Trustee or any of their immediate family members owned beneficially or of record any class of securities of EVC, EVD, any sub-adviser, if applicable, or any person controlling, controlled by or under common control with EVC or EVD or any sub-adviser, if applicable, collectively (“Affiliated Entity”).

During the calendar years ended December 31, 2016 and December 31, 2017, no noninterested Trustee (or their immediate family members) had:

(1)

Any direct or indirect interest in any Affiliated Entity;

(2)

Any direct or indirect material interest in any transaction or series of similar transactions with (i) the Trust; (ii) another fund managed or distributed by any Affiliated Entity; (iii) any Affiliated Entity; or (iv) an officer of any of the above; or

(3)

Any direct or indirect relationship with (i) the Trust; (ii) another fund managed or distributed by any Affiliated Entity; (iii) any Affiliated Entity; or (iv) an officer of any of the above.

During the calendar years ended December 31, 2016 and December 31, 2017, no officer of any Affiliated Entity served on the Board of Directors of a company where a noninterested Trustee of the Trust or any of their immediate family members served as an officer.

Noninterested Trustees may elect to defer receipt of all or a percentage of their annual fees in accordance with the terms of a Trustees Deferred Compensation Plan (the “Deferred Compensation Plan”). Under the Deferred Compensation Plan, an eligible Board member may elect to have his or her deferred fees invested in the shares of one or more funds in the Eaton Vance family of funds, and the amount paid to the Board members under the Deferred Compensation Plan will be determined based upon the performance of such investments. Deferral of Board members’ fees in accordance with the Deferred Compensation Plan will have a negligible effect on the assets, liabilities, and net income of a participating fund or portfolio, and do not require that a participating Board member be retained. There is no retirement plan for Board members.

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The fees and expenses of the Trustees of the Trust are paid by the Trust. (A Board member who is a member of the Eaton Vance organization receives no compensation from the Trust.) During the fiscal year ended June 30, 2018, the Trustees of the Trust earned the following compensation in their capacities as Board members from the Trust. For the year ended December 31, 2017, the Board members earned the following compensation in their capacities as members of the Eaton Vance Fund Boards⁽¹⁾:

Source of Compensation	Mark R. Fetting	Cynthia E. Frost	George J. Gorman	Valerie A. Mosley	William H. Park	Helen Frame Peters	Keith Quinton	Marcus L. Smith	Susan J. Sutherland	Harriett Tee Taggart	Scott E. Wennerholm
Trust	$1,942	$1,984	$2,123	$1,942⁽²⁾	$2,695	$2,081	$1,942	$1,942	$2,074⁽³⁾	$2,123	$2,042⁽⁴⁾
Trust and Fund Complex⁽¹⁾	$313,750	$313,750	$343,750	$313,750⁽⁵⁾	$438,750	$343,750	$313,750	$313,750	$321,250⁽⁶⁾	$343,750	$316,250⁽⁷⁾

⁽¹⁾

As of [_____], 2018, the Eaton Vance fund complex consists of [174] registered investment companies or series thereof. Messrs. Quinton and Smith began serving as Trustees effective October 1, 2018, and thus the compensation figures listed for the Trust and Fund Complex are estimated based on amounts each would have received if they had been Trustees for the fiscal year ended June 30, 2018 and for the calendar year ended December 31, 2017. Ralph F. Verni retired as a Trustee effective July 1, 2017. For the fiscal year ended June 30, 2018, Mr. Verni received Trustees fees of $566 from the Trust. For the calendar year ended December 31, 2017, he received $256,250 from the Trust and Fund Complex. Scott E. Eston retired as a Trustee effective September 30, 2017. For the fiscal year ended June 30, 2018, Mr. Eston received Trustees fees of $1,115 from the Trust. For the calendar year ended December 31, 2017, he received $341,250 from the Trust and Fund Complex.

⁽²⁾

Includes $451 of deferred compensation.

⁽³⁾

Includes $2,074 of deferred compensation.

⁽⁴⁾

Includes $612 of deferred compensation.

⁽⁵⁾

Includes $94,125 of deferred compensation.

⁽⁶⁾

Includes $316,231 of deferred compensation.

⁽⁷⁾

Includes $164,858 of deferred compensation.

Proxy Voting Policy. The Board adopted a proxy voting policy and procedures (the “Trust Policy”), pursuant to which the Board has delegated proxy voting responsibility to the Adviser and adopted the Adviser’s proxy voting policies and procedures (the “Adviser Policies”). An independent proxy voting service has been retained to assist in the voting of Trust proxies through the provision of vote analysis, implementation and recordkeeping and disclosure services. The members of the Board will review the Trust’s proxy voting records from time to time and will annually consider approving the Adviser Policies for the upcoming year. For a copy of the Trust Policy and the Adviser Policies, see Appendix B. Pursuant to certain provisions of the 1940 Act and certain exemptive orders relating to funds investing in other funds, a Trust may be required or may elect to vote its interest in another fund in the same proportion as the holders of all other shares of that fund. Information on how the Trust voted proxies relating to portfolio securities during the most recent 12-month period ended June 30 is available (1) without charge, upon request, by calling 1-800-262-1122, and (2) on the SEC’s website at http://www.sec.gov.

INVESTMENT ADVISORY AND OTHER SERVICES

The Adviser. Eaton Vance, its affiliates and its predecessor companies have been managing assets of individuals and institutions since 1924 and of investment companies since 1931. They maintain a large staff of experienced fixed-income, senior loan and equity investment professionals to service the needs of their clients. The fixed-income group focuses on all kinds of taxable investment-grade and high-yield securities, tax-exempt investment-grade and high-yield securities, and U.S. Government securities. The senior loan group focuses on senior floating rate loans, unsecured loans and other floating rate debt securities such as notes, bonds and asset-backed securities. The equity group covers stocks ranging from blue chip to emerging growth companies. Eaton Vance and its affiliates act as adviser to a family of mutual funds, and individual and various institutional accounts, including corporations, hospitals, retirement plans, universities, foundations and trusts.

The Trust will be responsible for all of its costs and expenses not expressly stated to be payable by Eaton Vance under the Investment Advisory Agreement (the “Advisory Agreement”) or the Amended and Restated Administrative Services Agreement (the “Administration Agreement”). Such costs and expenses to be borne by the Trust include, without limitation: (i) expenses of maintaining the Trust and continuing its existence; (ii) commissions, fees and other expenses connected with the acquisition and disposition of securities and other investments; (iii) auditing, accounting and legal expenses; (iv) taxes and interest; (v) governmental fees; (vi) expenses of repurchase and redemption (if any) of shares, including all expenses incurred in conducting repurchase and tender offers for the purpose of repurchasing Trust shares; (vii) expenses of registering and qualifying the Trust and its shares under federal and state securities laws and of

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preparing registration statements and amendments for such purposes, and fees and expenses of registering and maintaining registrations of the Trust under state securities laws; (viii) registration of the Trust under the Investment Company Act of 1940; (ix) expenses of reports and notices to shareholders and of meetings of shareholders and proxy solicitations therefor; (x) expenses of reports to regulatory bodies; (xi) insurance expenses; (xii) association membership dues; (xiii) fees, expenses and disbursements of custodians and subcustodians for all services to the Trust (including without limitation safekeeping of funds, securities and other investments, keeping of books and accounts and determination of net asset values); (xiv) fees, expenses and disbursements of transfer agents, dividend disbursing agents, shareholder servicing agents and registrars for all services to the Trust; (xv) expenses of listing shares with a stock exchange; (xvi) any direct charges to shareholders approved by the Trustees of the Trust; (xvii) compensation and expenses of Trustees of the Trust who are not members of the Administrator’s organization; (xviii) all payments to be made and expenses to be assumed by the Trust in connection with the distribution of Trust shares; (xix) any pricing and valuation services employed by the Trust to value its investments including primary and comparative valuation services; (xx) any investment advisory, sub-advisory or similar management fee payable by the Trust; (xxi) all expenses incurred in connection with the Trust’s use of a line of credit, or issuing and maintaining preferred shares; and (xxii) such non-recurring items as may arise, including expenses incurred in Trust connection with litigation, proceedings and claims and the obligation of the Trust to indemnify its Trustees and officers with respect thereto.

The Advisory Agreement with the Adviser continues in effect indefinitely so long as such continuance is approved at least annually (i) by the vote of a majority of those Trustees of the Trust who are not interested persons of the Adviser or the Trust cast in person at a meeting specifically called for the purpose of voting on such approval and (ii) by the Trust’s Board or by vote of a majority of the outstanding voting securities of the Trust. The Trust’s Administration Agreement continues in effect indefinitely thereafter so long as such continuance is approved at least annually by (i) the Trust’s Board and (ii) the vote of a majority of those Trustees of the Trust who are not interested persons of the Eaton Vance or the Trust. Each agreement may be terminated at any time without penalty on sixty (60) days’ written notice by the Trustees of the Trust or Eaton Vance, as applicable, or by vote of the majority of the outstanding shares of the Trust. Each agreement will terminate automatically in the event of its assignment. The Advisory Agreement provides that, in the absence of willful misfeasance, bad faith, gross negligence or reckless disregard of its obligations or duties to the Trust under the Advisory Agreement on the part of Eaton Vance, Eaton Vance shall not be subject to liability to the Trust or to any shareholder of the Trust for any act or omission in the course of, or connected with, rendering services hereunder or for any losses that may be sustained in the acquisition, holding or disposition of any interest in a loan or of any security, investment or other asset. The Administration Agreement provides that in the absence of willful misfeasance, bad faith, gross negligence or reckless disregard of its obligations or duties to the Trust under the Administration Agreement on the part of the Eaton Vance, Eaton Vance shall not be subject to liability to the Trust or to any shareholder of the Trust for any act or omission in the course of, or connected with, rendering services under the Administration Agreement or for any losses which may be sustained in the acquisition, holding or disposition of any security or other investment.

As of May 1, 2018, pursuant to the investment advisory agreement and subsequent fee reduction agreement between the Trust and Eaton Vance, the advisory fee is computed at an annual rate of 0.76% of the Trust’s average weekly gross assets. The annual adviser fee rate will be reduced by 0.01% every May 1 to May 1, 2039. As of June 30, 2018, the Trust had net assets of $272,015,732. For the fiscal years ended June 30, 2018, 2017 and 2016, the Trust incurred $3,232,473, $3,185,811 and $3,209,892, respectively, in advisory fees.

The administration fee is earned by Eaton Vance for administering the business affairs of the Trust and is computed at an annual rate of 0.25% of the Trust’s average weekly gross assets. For the fiscal years ended June 30, 2018, 2017 and 2016, Eaton Vance earned administration fees from the Trust of $1,051,810, $1,023,334 and $1,017,845, respectively.

Information About Eaton Vance. Eaton Vance is a business trust organized under the laws of The Commonwealth of Massachusetts. EV serves as trustee of Eaton Vance. EV and Eaton Vance are wholly-owned subsidiaries of EVC, a Maryland corporation and publicly-held holding company. BMR is an indirect subsidiary of EVC. EVC through its subsidiaries and affiliates engages primarily in investment management, administration and marketing activities. The Directors of EVC are Thomas E. Faust Jr., Ann E. Berman, Leo I. Higdon, Jr., Paula A. Johnson, Brian D. Langstraat, Dorothy E. Puhy, Winthrop H. Smith, Jr. and Richard A. Spillane, Jr. All shares of the outstanding Voting Common Stock of EVC are deposited in a Voting Trust, the Voting Trustees of which are Mr. Faust, Craig R. Brandon, Daniel C. Cataldo, Michael A. Cirami, Cynthia J. Clemson, James H. Evans, Maureen A. Gemma, Laurie G. Hylton, Mr. Langstraat, Frederick S. Marius, David C. McCabe, Scott H. Page, Edward J. Perkin, Lewis R. Piantedosi, Charles B. Reed, Craig P. Russ, John L. Shea, Eric A. Stein, Payson F. Swaffield, Michael W. Weilheimer, R. Kelly Williams and Matthew J. Witkos (all of whom are officers of Eaton Vance or its affiliates). The Voting Trustees have unrestricted voting rights for the election of Directors of EVC. All of the outstanding voting trust receipts issued under said Voting Trust are owned by certain of the officers of Eaton Vance who may also be officers, or officers and Directors of EVC and EV. As indicated under “Management and Organization,” all of the officers of the Trust (as well as Mr. Faust who is also a Trustee) hold positions in the Eaton Vance organization.

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Code of Ethics. The Adviser and the Trust have adopted Codes of Ethics (the “Codes”) governing personal securities transactions pursuant to Rule 17j-1 under the 1940 Act. Under the Codes, employees of the Adviser may purchase and sell securities (including securities held or eligible for purchase by the Trust) subject to the provisions of the Codes and certain employees are also subject to pre-clearance, reporting requirements and/or other procedures.

The Codes can be reviewed and copied at the Securities and Exchange Commission’s public reference room in Washington, DC (call 1-202-551-8090 for information on the operation of the public reference room); on the EDGAR Database on the SEC’s Internet site (http://www.sec.gov); or, upon payment of copying fees, by writing the SEC’s public reference section, Washington, DC 20549-1520, or by electronic mail at publicinfo@sec.gov.

Portfolio Managers. The portfolio managers of the Trust are listed below. The following table shows, as of the Trust’s most recent fiscal year end, the number of accounts each portfolio manager managed in each of the listed categories and the total assets (in millions of dollars) in the accounts managed within each category. The table also shows the number of accounts with respect to which the advisory fee is based on the performance of the account, if any, and the total assets (in millions of dollars) in those accounts.

	Number of All Accounts	Total Assets of All Accounts	Number of Accounts Paying a Performance Fee	Total Assets of Accounts Paying a Performance Fee
Scott H. Page
Registered Investment Companies	13	$32,896.7	0	$0
Other Pooled Investment Vehicles	13	$8,755.4	1	$2.4
Other Accounts	6	$6,426.5	0	$0
John P. Redding
Registered Investment Companies	1	$469.0	0	$0
Other Pooled Investment Vehicles	2	$49.4	0	$0
Other Accounts	0	$0	0	$0

The following table shows the dollar range of shares of the Trust beneficially owned by each portfolio manager as of the Trust’s most recent fiscal year ended June 30, 2018 and in the Eaton Vance Family of Funds as of December 31, 2017.

Portfolio Managers	Dollar Range of Equity Securities Beneficially Owned in the Trust	Aggregate Dollar Range of Equity Securities Beneficially Owned in all Registered Funds in the Eaton Vance Family of Funds
Scott H. Page	$100,001 - $500,000	Over $1,000,000
John P. Redding	$100,001 - $500,000	Over $1,000,000

It is possible that conflicts of interest may arise in connection with a portfolio manager’s management of the Trust’s investments on the one hand and the investments of other accounts for which a portfolio manager is responsible on the other. For example, a portfolio manager may have conflicts of interest in allocating management time, resources and investment opportunities among the Trust and other accounts he advises. In addition, due to differences in the investment strategies or restrictions between the Trust and the other accounts, the portfolio manager may take action with respect to another account that differs from the action taken with respect to the Trust. In some cases, another account managed by a portfolio manager may compensate the investment adviser based on the performance of the securities held by that account. The existence of such a performance based fee may create additional conflicts of interest for the portfolio manager in the allocation of management time, resources and investment opportunities. Whenever conflicts of interest arise, the portfolio manager will endeavor to exercise his discretion in a manner that he believes is equitable to all interested persons. The Adviser has adopted several policies and procedures designed to address these potential conflicts including a code of ethics and policies that govern the investment adviser's trading practices, including among other things the aggregation and allocation of trades among clients, brokerage allocations, cross trades and best execution.

Eaton Vance Senior Income Trust

SAI dated [_____], 2018

Compensation Structure for Eaton Vance. Compensation of the Adviser's portfolio managers and other investment professionals has three primary components: (1) a base salary, (2) an annual cash bonus, (3) annual non-cash compensation consisting of options to purchase shares of EVC nonvoting common stock and/or restricted shares of EVC nonvoting common stock that generally are subject to a vesting schedule and (4) (for equity portfolio managers) a Deferred Alpha Incentive Plan, which pays a deferred cash award tied to future excess returns in certain equity strategy portfolios. The Adviser’s investment professionals also receive certain retirement, insurance and other benefits that are broadly available to the Adviser’s employees. Compensation of the Adviser’s investment professionals is reviewed primarily on an annual basis. Cash bonuses, stock-based compensation awards, and adjustments in base salary are typically paid or put into effect at or shortly after the October 31st fiscal year end of EVC.

Method to Determine Compensation. The Adviser compensates its portfolio managers based primarily on the scale and complexity of their portfolio responsibilities and the total return performance of managed funds and accounts versus the benchmark(s) stated in the prospectus, as well as an appropriate peer group (as described below). In addition to rankings within peer groups of funds on the basis of absolute performance, consideration may also be given to relative risk-adjusted performance. Risk-adjusted performance measures include, but are not limited to, the Sharpe ratio (Sharpe ratio uses standard deviation and excess return to determine reward per unit of risk). Performance is normally based on periods ending on the September 30th preceding fiscal year end. Fund performance is normally evaluated primarily versus peer groups of funds as determined by Lipper Inc. and/or Morningstar, Inc. When a fund’s peer group as determined by Lipper or Morningstar is deemed by the Adviser’s management not to provide a fair comparison, performance may instead be evaluated primarily against a custom peer group or market index. In evaluating the performance of a fund and its manager, primary emphasis is normally placed on three-year performance, with secondary consideration of performance over longer and shorter periods. For funds that are tax-managed or otherwise have an objective of after-tax returns, performance is measured net of taxes. For other funds, performance is evaluated on a pre-tax basis. For funds with an investment objective other than total return (such as current income), consideration will also be given to the fund’s success in achieving its objective. For managers responsible for multiple funds and accounts, investment performance is evaluated on an aggregate basis, based on averages or weighted averages among managed funds and accounts. Funds and accounts that have performance-based advisory fees are not accorded disproportionate weightings in measuring aggregate portfolio manager performance. A portion of the compensation payable to equity portfolio managers and investment professionals will be determined based on the ability of one or more accounts managed by such manager to achieve a specified target average annual gross return over a three year period in excess of the account benchmark. The cash award to be payable at the end of the three year term will be established at the inception of the term and will be adjusted positively or negatively to the extent that the average annual gross return varies from the specified target return.

The compensation of portfolio managers with other job responsibilities (such as heading an investment group or providing analytical support to other portfolios) will include consideration of the scope of such responsibilities and the managers’ performance in meeting them.

The Adviser seeks to compensate portfolio managers commensurate with their responsibilities and performance, and competitive with other firms within the investment management industry. The Adviser participates in investment-industry compensation surveys and utilizes survey data as a factor in determining salary, bonus and stock-based compensation levels for portfolio managers and other investment professionals. Salaries, bonuses and stock-based compensation are also influenced by the operating performance of the Adviser and its parent company. The overall annual cash bonus pool is generally based on a substantially fixed percentage of pre-bonus adjusted operating income. While the salaries of the Adviser’s portfolio managers are comparatively fixed, cash bonuses and stock-based compensation may fluctuate significantly from year to year, based on changes in manager performance and other factors as described herein. For a high performing portfolio manager, cash bonuses and stock-based compensation may represent a substantial portion of total compensation.

Investment Advisory Services. Under the general supervision of the Trust’s Board, Eaton Vance will carry out the investment and reinvestment of the assets of the Trust, will furnish continuously an investment program with respect to the Trust, will determine which securities should be purchased, sold or exchanged, and will implement such determinations. Eaton Vance will furnish to the Trust investment advice and provide related office facilities and personnel for servicing the investments of the Trust. Eaton Vance will compensate all Trustees and officers of the Trust who are members of the Eaton Vance organization and who render investment services to the Trust, and will also compensate all other Eaton Vance personnel who provide research and investment services to the Trust.

Eaton Vance Senior Income Trust

SAI dated [_____], 2018

Commodity Futures Trading Commission Registration. Effective December 31, 2012, the Commodity Futures Trading Commission (“CFTC”) adopted certain regulatory changes that subject registered investment companies and advisers to regulation by the CFTC if a fund invests more than a prescribed level of its assets in certain CFTC-regulated instruments (including futures, certain options and swaps agreements) or markets itself as providing investment exposure to such instruments. The Trust has claimed an exclusion from the definition of the term “commodity pool operator” under the Commodity Exchange Act. Accordingly, neither the Trust nor the Adviser with respect to the operation of the Trust is subject to CFTC regulation. Because of its management of other strategies, Eaton Vance is registered with the CFTC as a commodity pool operator. Eaton Vance is also registered as a commodity trading advisor. The CFTC has neither reviewed nor approved the Trust's investment strategies or this SAI.

Administrative Services. Under the Administration Agreement, Eaton Vance is responsible for managing the business affairs of the Trust, subject to the supervision of the Trust’s Board. Eaton Vance will furnish to the Trust all office facilities, equipment and personnel for administering the affairs of the Trust. Eaton Vance will compensate all Trustees and officers of the Trust who are members of the Eaton Vance organization and who render executive and administrative services to the Trust, and will also compensate all other Eaton Vance personnel who perform management and administrative services for the Trust. Eaton Vance’s administrative services include recordkeeping, preparation and filing of documents required to comply with federal and state securities laws, supervising the activities of the Trust’s custodian and transfer agent, providing assistance in connection with the Trustees and shareholders’ meetings, providing services in connection with repurchase offers, if any, and other administrative services necessary to conduct the Trust’s business.

DETERMINATION OF NET ASSET VALUE

The net asset value of the Trust is determined by State Street Bank and Trust Company (as agent and custodian) by subtracting the liabilities of the Trust from the value of its total assets. The Trust is closed for business and will not issue a net asset value on the following business holidays and any other business day that the New York Stock Exchange (the “Exchange”) is closed: New Year’s Day, Martin Luther King, Jr. Day, Presidents’ Day, Good Friday, Memorial Day, Independence Day, Labor Day, Thanksgiving Day and Christmas Day.

The Board has approved procedures pursuant to which investments are valued for purposes of determining the Trust’s net asset value. Listed below is a summary of the methods generally used to value investments (some or all of which may be held by the Trust) under the procedures.

Equity securities (including common stock, exchange-traded funds, closed end funds, preferred equity securities, exchange-traded notes and other instruments that trade on recognized stock exchanges) are valued at the last sale, official close or if there are no reported sales at the mean between the bid and asked price on the primary exchange on which they are traded.

Most debt obligations are valued on the basis of market valuations furnished by a pricing service or at the mean of the bid and asked prices provided by recognized broker/dealers of such securities. The pricing service may use a pricing matrix to determine valuation.

Short-term instruments with remaining maturities of less than 397 days are valued on the basis of market valuations furnished by a pricing service or based on dealer quotations.

Foreign securities and currencies are valued in U.S. dollars based on foreign currency exchange quotations supplied by a pricing service.

Senior and Junior Loans are valued on the basis of prices furnished by a pricing service. The pricing service uses transactions and market quotations from brokers in determining values.

Futures contracts are valued at the settlement or closing price on the primary exchange or board of trade on which they are traded.

Exchange-traded options are valued at the mean of the bid and asked prices. Over-the-counter options are valued based on quotations obtained from a pricing service or from a broker (typically the counterparty to the option).

Non-exchange traded derivatives (including swap agreements, forward contracts and equity participation notes) are generally valued on the basis of valuations provided by a pricing service or using quotes provided by a broker/dealer (typically the counterparty).

Precious metals are valued at the New York Composite mean quotation.

Eaton Vance Senior Income Trust

SAI dated [_____], 2018

Liabilities with a payment or maturity date of 364 days or less are stated at their principal value and longer dated liabilities generally will be carried at their fair value.

Valuations of foreign equity securities and total return swaps and exchange-traded futures contracts on non-North American equity indices may be adjusted from prices in effect at the close of trading on foreign exchanges to more accurately reflect their fair value as of the close of regular trading on the Exchange. Such fair valuations may be based on information provided by a pricing service.

Investments which are unable to be valued in accordance with the foregoing methodologies are valued at fair value using methods determined in good faith by or at the direction of the members of the Board. Such methods may include consideration of relevant factors, including but not limited to (i) the type of security, the existence of any contractual restrictions on the security’s disposition, (ii) the price and extent of public trading in similar securities of the issuer or of comparable companies or entities, (iii) quotations or relevant information obtained from broker-dealers or other market participants, (iv) information obtained from the issuer, analysts, and/or the appropriate stock exchange (for exchange-traded securities), (v) an analysis of the company’s or entity’s financial condition, (vi) an evaluation of the forces that influence the issuer and the market(s) in which the security is purchased and sold (vii) an analysis of the terms of any transaction involving the issuer of such securities; and (viii) any other factors deemed relevant by the investment adviser. The portfolio managers of one Eaton Vance fund that invests in Senior and Junior Loans may not possess the same information about a Senior or Junior Loan as the portfolio managers of another Eaton Vance fund. As such, at times the fair value of a Loan determined by certain Eaton Vance portfolio managers may vary from the fair value of the same Loan determined by other portfolio managers.

The Trust may invest in Eaton Vance Cash Reserves Fund, LLC (Cash Reserves Fund), an affiliated investment company managed by Eaton Vance. Cash Reserves Fund generally values its investment securities utilizing the amortized cost valuation technique in accordance with Rule 2a-7 under the 1940 Act. This technique involves initially valuing a portfolio security at its cost and thereafter assuming a constant amortization to maturity of any discount or premium. If amortized cost is determined not to approximate fair value, Cash Reserves Fund may value its investment securities in the same manner as debt obligations described above.

PORTFOLIO TRADING

The Trust will acquire Senior Loans from major international banks, selected domestic regional banks, insurance companies, finance companies and other financial institutions. In selecting financial institutions from which Senior Loans may be acquired, the investment adviser will consider, among other factors, the financial strength, professional ability, level of service and research capability of the institution. While these financial institutions are generally not required to repurchase Senior Loans which they have sold, they may act as principal or on an agency basis in connection with their sale by the Trust.

Decisions concerning the execution of portfolio security transactions, including the selection of the market and the broker-dealer firm, are made by the investment adviser. The Trust is responsible for the expenses associated with its portfolio transactions. The investment adviser is also responsible for the execution of transactions for all other accounts managed by it. The investment adviser places the portfolio security transactions for execution with one or more broker-dealer firms. The investment adviser uses its best efforts to obtain execution of portfolio security transactions at prices which in the investment adviser’s judgment are advantageous to the client and at a reasonably competitive spread or (when a disclosed commission is being charged) at reasonably competitive commission rates. In seeking such execution, the investment adviser will use its best judgment in evaluating the terms of a transaction, and will give consideration to various relevant factors, including without limitation the full range and quality of the broker-dealer firm’s services, responsiveness of the firm to the investment adviser, the size and type of the transaction, the nature and character of the market for the security, the confidentiality, speed and certainty of effective execution required for the transaction, the general execution and operational capabilities of the broker-dealer firm, the reputation, reliability, experience and financial condition of the firm, the value and quality of the services rendered by the firm in this and other transactions, and the amount of the spread or commission, if any. In addition, the investment adviser may consider the receipt of Research Services (as defined below), provided it does not compromise the investment adviser’s obligation to seek best overall execution for the Trust and is otherwise in compliance with applicable law. The investment adviser may engage in portfolio brokerage transactions with a broker-dealer firm that sells shares of Eaton Vance funds, provided such transactions are not directed to that firm as compensation for the promotion or sale of such shares.

Transactions on stock exchanges and other agency transactions involve the payment of negotiated brokerage commissions. Such commissions vary among different broker-dealer firms, and a particular broker-dealer may charge different commissions according to such factors as the difficulty and size of the transaction and the volume of business done with such broker-dealer. Transactions in foreign securities often involve the payment of brokerage commissions,

Eaton Vance Senior Income Trust

SAI dated [_____], 2018

which may be higher than those in the United States. There is generally no stated commission in the case of securities traded in the over-the-counter markets including transactions in fixed-income securities which are generally purchased and sold on a net basis (i.e., without commission) through broker-dealers and banks acting for their own account rather than as brokers. Such firms attempt to profit from such transactions by buying at the bid price and selling at the higher asked price of the market for such obligations, and the difference between the bid and asked price is customarily referred to as the spread. Fixed-income transactions may also be transacted directly with the issuer of the obligations. In an underwritten offering the price paid often includes a disclosed fixed commission or discount retained by the underwriter or dealer. Although spreads or commissions paid on portfolio security transactions will, in the judgment of the investment adviser, be reasonable in relation to the value of the services provided, commissions exceeding those which another firm might charge may be paid to broker-dealers who were selected to execute transactions on behalf of the investment adviser’s clients in part for providing brokerage and research services to the investment adviser as permitted by applicable law.

Pursuant to the safe harbor provided in Section 28(e) of the Securities Exchange Act of 1934, as amended (“Section 28(e)”) and to the extent permitted by other applicable law, a broker or dealer who executes a portfolio transaction on behalf of the investment adviser client may receive a commission that is in excess of the amount of commission another broker or dealer would have charged for effecting that transaction if the investment adviser determines in good faith that such compensation was reasonable in relation to the value of the brokerage and research services provided. This determination may be made on the basis of either that particular transaction or on the basis of the overall responsibility which the investment adviser and its affiliates have for accounts over which they exercise investment discretion. “Research Services” as used herein includes any and all brokerage and research services to the extent permitted by Section 28(e) and other applicable law. Generally, Research Services may include, but are not limited to, such matters as research, analytical and quotation services, data, information and other services products and materials which assist the investment adviser in the performance of its investment responsibilities. More specifically, Research Services may include general economic, political, business and market information, industry and company reviews, evaluations of securities and portfolio strategies and transactions, technical analysis of various aspects of the securities markets, recommendations as to the purchase and sale of securities and other portfolio transactions, certain financial, industry and trade publications, certain news and information services, and certain research oriented computer software, data bases and services. Any particular Research Service obtained through a broker-dealer may be used by the investment adviser in connection with client accounts other than those accounts which pay commissions to such broker-dealer, to the extent permitted by applicable law. Any such Research Service may be broadly useful and of value to the investment adviser in rendering investment advisory services to all or a significant portion of its clients, or may be relevant and useful for the management of only one client’s account or of a few clients’ accounts, or may be useful for the management of merely a segment of certain clients’ accounts, regardless of whether any such account or accounts paid commissions to the broker-dealer through which such Research Service was obtained. The investment adviser evaluates the nature and quality of the various Research Services obtained through broker-dealer firms and, to the extent permitted by applicable law, may attempt to allocate sufficient portfolio security transactions to such firms to ensure the continued receipt of Research Services which the investment adviser believes are useful or of value to it in rendering investment advisory services to its clients. The investment adviser may also receive brokerage and Research Services from underwriters and dealers in fixed-price offerings, when permitted under applicable law.

Research Services provided by (and produced by) broker-dealers that execute portfolio transactions or from affiliates of executing broker-dealers are referred to as “Proprietary Research.” Except for trades executed in jurisdictions where such consideration is not permissible, the investment adviser may and does consider the receipt of Proprietary Research Services as a factor in selecting broker dealers to execute client portfolio transactions, provided it does not compromise the investment adviser’s obligation to seek best overall execution. In jurisdictions where permissible, the investment adviser also may consider the receipt of Research Services under so called “client commission arrangements” or “commission sharing arrangements” (both referred to as “CCAs”) as a factor in selecting broker dealers to execute transactions, provided it does not compromise the investment adviser’s obligation to seek best overall execution. Under a CCA arrangement, the investment adviser may cause client accounts to effect transactions through a broker-dealer and request that the broker-dealer allocate a portion of the commissions paid on those transactions to a pool of commission credits that are paid to other firms that provide Research Services to the investment adviser. Under a CCA, the broker-dealer that provides the Research Services need not execute the trade. Participating in CCAs may enable the investment adviser to consolidate payments for research using accumulated client commission credits from transactions executed through a particular broker-dealer to periodically pay for Research Services obtained from and provided by other firms, including other broker-dealers that supply Research Services. The investment adviser believes that CCAs offer the potential to optimize the execution of trades and the acquisition of a variety of high quality Research Services that the investment adviser might not be provided access to absent CCAs. The investment adviser will only enter into and utilize CCAs to the extent permitted by Section 28(e) and other applicable law.

Eaton Vance Senior Income Trust

SAI dated [_____], 2018

Fund trades executed by an affiliate of the investment adviser licensed in the United Kingdom may implicate laws of the United Kingdom, including rules of the UK Financial Conduct Authority, which govern client trading commissions and Research Services (“UK Law”). Broadly speaking, under UK Law the investment adviser may not accept any good or service when executing an order unless that good or service either is directly related to the execution of trades on behalf of its clients/customers or amounts to the provision of substantive research (as defined under UK Law). These requirements may also apply with respect to orders in connection with which the investment adviser receives goods and services under a CCA or other bundled brokerage arrangement. Fund trades may also implicate UK Law requiring the investment adviser to direct any research portion of a brokerage commission to an account controlled by the investment adviser.

The investment companies sponsored by the investment adviser or its affiliates also may allocate brokerage commissions to acquire information relating to the performance, fees and expenses of such companies and other investment companies, which information is used by the members of the Board of such companies to fulfill their responsibility to oversee the quality of the services provided to various entities, including the investment adviser, to such companies. Such companies may also pay cash for such information.

Securities considered as investments for the Trust may also be appropriate for other investment accounts managed by the investment adviser or its affiliates. Whenever decisions are made to buy or sell securities by the Trust and one or more of such other accounts simultaneously, the investment adviser will allocate the security transactions (including “new” issues) in a manner which it believes to be equitable under the circumstances. As a result of such allocations, there may be instances where the Trust will not participate in a transaction that is allocated among other accounts. If an aggregated order cannot be filled completely, allocations will generally be made on a pro rata basis. An order may not be allocated on a pro rata basis where, for example: (i) consideration is given to portfolio managers who have been instrumental in developing or negotiating a particular investment; (ii) consideration is given to an account with specialized investment policies that coincide with the particulars of a specific investment; (iii) pro rata allocation would result in odd-lot or de minimis amounts being allocated to a portfolio or other client; or (iv) where the investment adviser reasonably determines that departure from a pro rata allocation is advisable. While these aggregation and allocation policies could have a detrimental effect on the price or amount of the securities available to the Trust from time to time, it is the opinion of the members of the Board that the benefits from the investment adviser organization outweigh any disadvantage that may arise from exposure to simultaneous transactions.

The following table shows brokerage commissions paid during the fiscal years ended June 30, 2018, 2017 and 2016, as well as the amount of Trust security transactions for the most recent fiscal year (if any) that were directed to firms that provided some Research Services to the investment adviser or its affiliates (see above), and the commissions paid in connection therewith.

Fiscal Year End	Brokerage Commission Paid	Amount of Transactions Directed to Firms Providing Research	Commissions Paid on Transactions Directed to Firms Providing Research
June 30, 2018	$75	$231,245	$72
June 30, 2017	$750
June 30, 2016	$22

During the fiscal year ended June 30, 2018, the Trust held no securities of its “regular brokers or dealers”, as that term is defined in Rule 10b-1 of the 1940 Act.

TAXES

The Trust intends to qualify each year as a regulated investment company (“RIC”) under the Internal Revenue Code of 1986, as amended (the “Code”). Accordingly, the Trust intends to satisfy certain requirements relating to sources of its income and diversification of its assets and to distribute substantially all of its net income and net short-term and long-term capital gains (after reduction by any available capital loss carryforwards) in accordance with the timing requirements imposed by the Code, so as to maintain its RIC status and to avoid paying any federal income or excise tax. To the extent it qualifies for treatment as a RIC and satisfies the above-mentioned distribution requirements, the Trust will not be subject to federal income tax on income paid to its shareholders in the form of dividends or capital gain distributions.

To qualify as a RIC for federal income tax purposes, the Trust must derive at least 90% of its annual gross income from dividends, interest, payments with respect to securities loans, gains from the sale or other disposition of stock, securities or foreign currencies, or other income (including, but not limited to, gains from options, futures or forward contracts) derived with respect to its business of investing in stock, securities and currencies, and net income derived from an interest in a qualified publicly traded partnership. The Trust must also distribute to its shareholders at least the sum of 90% of its investment company taxable income and 90% of its net tax-exempt interest income for each taxable year.

Eaton Vance Senior Income Trust

SAI dated [_____], 2018

The Trust must also satisfy certain requirements with respect to the diversification of its assets. The Trust must have, at the close of each quarter of its taxable year, at least 50% of the value of its total assets represented by cash and cash items, U.S. government securities, securities of other RICs, and other securities that, in respect of any one issuer, do not represent more than 5% of the value of the assets of the Trust or more than 10% of the voting securities of that issuer. In addition, at those times, not more than 25% of the value of the Trust’s assets may be invested in securities (other than U.S. Government securities or the securities of other RICs) of any one issuer, or of two or more issuers that the Trust controls and which are engaged in the same or similar trades or businesses or related trades or businesses, or of one or more qualified publicly traded partnerships. For purposes of asset diversification testing, obligations issued or guaranteed by certain agencies or instrumentalities of the U.S. government, such as the Federal Agricultural Mortgage Corporation, the Federal Farm Credit System Financial Assistance Corporation, Federal Home Loan Banks, Federal Home Loan Mortgage Corporation, Federal National Mortgage Association, Government National Mortgage Association, and Student Loan Marketing Corporation are treated as U.S. government securities.

The Trust also seeks to avoid the imposition of a federal excise tax on its ordinary income and capital gain net income. However, if the Trust fails to distribute in a calendar year substantially all of its ordinary income for such year and substantially all of its capital gain net income for the one-year period ending October 31 (or later if the Trust is permitted so to elect and so elects), plus any retained amount from the prior year, the Trust will be subject to a 4% excise tax on the undistributed amounts. In order to avoid incurring a federal excise tax obligation, the Code requires that a RIC distribute (or be deemed to have distributed) by December 31 of each calendar year (i) at least 98% of its ordinary income (not including tax-exempt income) for such year, (ii) at least 98.2% of its capital gain net income (which is the excess of its realized capital gains over its realized capital losses), generally computed on the basis of the one-year period ending on October 31 of such year, after reduction by any available capital loss carryforwards and (iii) 100% of any income and capital gains from the prior year (as previously computed) that were not distributed during such year and on which the Trust paid no federal income tax. If the Trust fails to meet these requirements it will be subject to a nondeductible 4% excise tax on the undistributed amounts. For the foregoing purposes, a RIC is treated as having distributed any amount on which it is subject to income tax for any tax year ending in such calendar year and, if it so elects, the amounts on which qualified estimated tax payments are made by it during such calendar year (in which case the amount it is treated as having distributed in the following calendar year will be reduced.)

The Trust intends to make monthly distributions of net investment income after payment of dividends on any outstanding preferred shares or interest on any outstanding borrowings. The Trust will distribute annually any net short-term capital gain (which is taxable as ordinary income) and any net capital gain. Distributions of the Trust's net capital gains (“capital gain dividends”), if any, are generally taxable to shareholders as long-term capital gains, regardless of the length of time shares have been held by shareholders. Dividends paid to shareholders out of the Trust's current and accumulated earnings and profits, except in the case of capital gain dividends and certain dividends received by individuals, will be taxable as ordinary income. Dividends with respect to the shares generally will not constitute “qualified dividends” for federal income tax purposes and thus will not be eligible for the favorable long-term capital gains tax rates. If, for any calendar year, the Trust's total distributions exceed the Trust's current and accumulated earnings and profits, the excess will be treated as a tax-free return of capital to each Common Shareholder (up to the amount of the Common Shareholder's basis in his or her Common Shares) and thereafter as gain from the sale of Common Shares (assuming the Common Shares are held as a capital asset). The amount treated as a tax-free return of capital will reduce the Common Shareholder's adjusted basis in his or her Common Shares, thereby increasing his or her potential gain or reducing his or her potential loss on the subsequent sale or other disposition of his or her Common Shares. See below for a summary of the maximum tax rates applicable to capital gains (including capital gain dividends). Dividends will not qualify for a dividends received deduction generally available to corporate shareholders.

If the Trust fails to meet the annual gross income test described above, the Trust would nevertheless be considered to have satisfied the test if (i) (a) such failure was due to reasonable cause and not due to willful neglect and (b) the Trust reported the failure pursuant to a schedule for such tax year filed in the manner provided by the Internal Revenue Service

Eaton Vance Senior Income Trust

SAI dated [_____], 2018

(“IRS”), and (ii) the Trust pays an excise tax equal to the excess non-qualifying income. If the Trust failed to meet the asset diversification test described above with respect to any quarter, the Trust would nevertheless be considered to have satisfied the requirements for such quarter if the Trust cured such failure within 6 months and either (i) such failure was de minimis or (ii) (a) such failure was due to reasonable cause and not due to willful neglect and (b) the Trust reports the failure pursuant to a schedule for the quarter filed as provided by the IRS and pays an excise tax.

The Trust may be subject to foreign withholding or other foreign taxes with respect to income (possibly including, in some cases, capital gains) on certain foreign securities. These taxes may be reduced or eliminated under the terms of an applicable U.S. income tax treaty. If more than 50% of the value of the total assets of the Trust consists of securities issued by foreign issuers, the Trust may be eligible to pass through to shareholders its proportionate share of any foreign taxes paid by the Trust, in which event shareholders will include in income, and will be entitled to take any foreign tax credits or deductions for, such foreign taxes.

The Trust's investment in zero coupon and certain other securities will cause it to realize income prior to the receipt of cash payments with respect to these securities. Such income will be accrued daily by the Trust and, in order to avoid a tax payable by the Trust, the Trust may be required to liquidate securities that it might otherwise have continued to hold in order to generate cash so that the Trust may make required distributions to its shareholders.

Any recognized gain or income attributable to market discount on long-term debt obligations (i.e., on obligations with a term of more than one year except to the extent of a portion of the discount attributable to original issue discount) purchased by the Trust is taxable as ordinary income. A long-term debt obligation is generally treated as acquired at a market discount if purchased after its original issue at a price less than (i) the stated principal amount payable at maturity, in the case of an obligation that does not have original issue discount or (ii) in the case of an obligation that does have original issue discount, the sum of the issue price and any original issue discount that accrued before the obligation was purchased, subject to a de minimis exclusion.

The Trust may invest a portion of its total assets in “high yield” securities, commonly known as “junk bonds.” Investments in these types of securities may present special tax issues for the Trust. Federal income tax rules are not entirely clear about issues such as when the Trust may cease to accrue interest, original issue discount or market discount, when and to what extent deductions may be taken for bad debts or worthless securities, how payments received on obligations in default should be allocated between principal and income and whether exchanges of debt obligations in a bankruptcy or workout context are taxable. These and other issues will be addressed by the Trust, in the event it invests in such debt securities, in order to seek to preserve its status as a RIC and to not become subject to U.S. federal income or excise tax.

The Trust's investments in options, futures contracts, hedging transactions, forward contracts (to the extent permitted) and certain other transactions will be subject to special tax rules (including mark-to-market, constructive sale, straddle, wash sale, short sale and other rules), the effect of which may be to accelerate income to the Trust, defer Trust losses, cause adjustments in the holding periods of securities held by the Trust, convert capital gain into ordinary income and convert short-term capital losses into long-term capital losses. These rules could therefore affect the amount, timing and character of distributions to shareholders. The Trust may be required to limit its activities in options and futures contracts in order to enable it to maintain its RIC status.

Selling shareholders will generally recognize gain or loss in an amount equal to the difference between the shareholder's adjusted tax basis in the shares sold and the amount received. If the shares are held as a capital asset, the gain or loss will be a capital gain or loss.

The maximum tax rate applicable to net capital gains recognized by individuals and other non-corporate taxpayers is (i) the same as the maximum ordinary income tax rate for gains recognized on the sale of capital assets held for one year or less, or (ii) 20% for gains recognized on the sale of capital assets held for more than one year (as well as certain capital gain dividends). Any loss on a disposition of shares held for six months or less will be treated as a long-term capital loss to the extent of any capital gain dividends received with respect to those shares. For purposes of determining whether shares have been held for six months or less, the holding period is suspended for any periods during which the shareholder's risk of loss is diminished as a result of holding one or more other positions in substantially similar or related

Eaton Vance Senior Income Trust

SAI dated [_____], 2018

property, or through certain options or short sales. Any loss realized on a sale or exchange of shares will be disallowed to the extent those shares are replaced by other shares within a period of 61 days beginning 30 days before and ending 30 days after the date of disposition of the shares (whether through the reinvestment of distributions, which could occur, for example, if the shareholder is a participant in the dividend reinvestment plan or otherwise). In that event, the basis of the replacement shares will be adjusted to reflect the disallowed loss.

Sales charges paid upon a purchase of shares cannot be taken into account for purposes of determining gain or loss on a sale of the shares before the 91st day after their purchase to the extent a sales charge is reduced or eliminated in a subsequent acquisition of shares of the Trust (or of another fund) during the period beginning on the date of such sale and ending on January 31 of the calendar year following the calendar year that includes the date of such sale pursuant to the reinvestment or exchange privilege. Any disregarded amounts will result in an adjustment to the shareholder's tax basis in some or all of any other shares acquired.

Certain net investment income received by an individual having adjusted gross income in excess of $200,000 (or $250,000 for married individuals filing jointly) will be subject to a tax of 3.8 percent. Undistributed net investment income of trusts and estates in excess of a specified amount also will be subject to this tax. Dividends and capital gains distributed by the Trust, and gain realized on the sale of shares, will constitute investment income of the type subject to this tax.

Dividends and distributions on the Trust's shares are generally subject to federal income tax as described herein to the extent they do not exceed the Trust's realized income and gains, even though such dividends and distributions may economically represent a return of a particular shareholder's investment. Such distributions are likely to occur in respect of shares purchased at a time when the Trust's net asset value reflects gains that are either unrealized, or realized but not distributed. Such realized gains may be required to be distributed even when the Trust's net asset value also reflects unrealized losses. Certain distributions declared in October, November or December and paid in the following January will be taxed to shareholders as if received on December 31 of the year in which they were declared. In addition, certain other distributions made after the close of a taxable year of the Trust may be “spilled back” and treated as paid by the Trust (except for purposes of the 4% excise tax) during such taxable year. In such case, shareholders will be treated as having received such dividends in the taxable year in which the distributions were actually made. Dividends paid out of the Trust's investment company taxable income are generally taxable to a shareholder as ordinary income to the extent of the Trust's earnings and profits. Dividends with respect to the shares generally will not constitute “qualified dividends” for federal income tax purposes and thus will not be eligible for the favorable long-term capital gains tax rates.

Amounts paid by the Trust to individuals and certain other shareholders who have not provided the Trust with their correct taxpayer identification number (“TIN”) and certain certifications required by the IRS as well as shareholders with respect to whom the Trust has received certain information from the IRS or a broker may be subject to “backup” withholding of federal income tax arising from the Trust's taxable dividends and other distributions as well as the gross proceeds of sales of shares. An individual's TIN is generally his or her social security number. Backup withholding is not an additional tax. Any amounts withheld under the backup withholding rules from payments made to a shareholder may be refunded or credited against such shareholder's U.S. federal income tax liability, if any, provided that the required information is furnished to the IRS and such shareholder makes a timely filing of an appropriate tax return or refund claim.

The Trust will inform shareholders of the source and tax status of all distributions promptly after the close of each calendar year. The IRS has taken the position that if a RIC has more than one class of shares, it may designate distributions made to each class in any year as consisting of no more than that class's proportionate share of particular types of income for that year, including ordinary income and net capital gain. A class's proportionate share of a particular type of income for a year is determined according to the percentage of total dividends paid by the RIC during that year to the class. Accordingly, the Trust intends to designate a portion of its distributions in capital gain dividends in accordance with the IRS position.

The Trust (or its administrative agent) is required to report to the IRS and furnish to shareholders the cost basis information and holding period for shares purchased on or after January 1, 2012, and redeemed by the Trust on or after that date. The Trust will permit shareholders to elect from among several permitted cost basis methods. In the absence of an election, the Trust will use a default cost basis method. The cost basis method a shareholder elects may not be changed with respect to a redemption of shares after the settlement date of the redemption. Shareholders should consult with their tax advisors to determine the best permitted cost basis method for their tax situation and to obtain more information about how the cost basis reporting rules apply to them.

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Properly reported dividends are generally exempt from U.S. federal withholding tax where they (i) are paid in respect of the Trust’s “qualified net interest income” (generally, the Trust’s U.S. source interest income, other than certain contingent interest and interest from obligations of a corporation or partnership in which the Trust is at least a 10% shareholder, reduced by expenses that are allocable to such income) or (ii) are paid in respect of the Trust’s “qualified short-term capital gains” (generally, the excess of the Trust’s net short-term capital gain over the Trust’s long-term capital loss for such taxable year). However, depending on its circumstances, the Trust may report all, some or none of its potentially eligible dividends as such qualified net interest income or as qualified short-term capital gains and/or treat such dividends, in whole or in part, as ineligible for this exemption from withholding. In order to qualify for this exemption from withholding, a non-U.S. shareholder would need to comply with applicable certification requirements relating to its non-U.S. status (including, in general, furnishing an IRS Form W-8BEN, IRS Form W-8BEN-E, or substitute Form). In the case of shares held through an intermediary, the intermediary could withhold even if the Trust designates the payment as qualified net interest income or qualified short-term capital gain. Non-U.S. shareholders should contact their intermediaries with respect to the application of these rules to their accounts.

The foregoing discussion may not address the special tax rules applicable to certain classes of investors, such as tax-exempt entities, foreign investors, insurance companies and financial institutions. Shareholders should consult their own tax advisers with respect to special tax rules that may apply in their particular situations, as well as the state, local, and, where applicable, foreign tax consequences of investing in the Trust.

Although the matter is not free from doubt, due to the absence of direct regulatory or judicial authority, the Trust intends to take the position that under current law the manner in which the Trust intends to allocate items of ordinary income and net capital gain among the Trust's Common Shares and APS will be respected for federal income tax purposes. It is possible that the IRS could disagree with this conclusion and attempt to reallocate the Trust's net capital gain or other taxable income.

Under Treasury Regulations, if a shareholder realizes a loss on disposition of the Trust’s shares of at least $2 million in any single taxable year or $4 million in any combination of taxable years for an individual shareholder or at least $10 million in any single taxable year or $20 million in any combination of taxable years for a corporate shareholder, the shareholder must file with the IRS a disclosure statement on Form 8886. Direct shareholders of portfolio securities are in many cases excepted from this reporting requirement, but under current guidance, shareholders of a RIC are not excepted. The fact that a loss is reportable under these regulations does not affect the legal determination of whether the taxpayer’s treatment of the loss is proper. Shareholders should consult their tax advisors to determine the applicability of these regulations in light of their individual circumstances. Under certain circumstances, certain tax-exempt entities and their managers may be subject to excise tax if they are parties to certain reportable transactions.

Compliance with FATCA. A 30% withholding tax is imposed on U.S.-source dividends, including those paid by the Trust and, after December 31, 2018, will be imposed on gross proceeds from the sale of property producing U.S.-source dividends, including interests in the Trust, to (i) foreign financial institutions including non-U.S. investment funds and foreign financial institutions acting as intermediaries unless they agree to collect and disclose to the IRS information regarding their direct and indirect U.S. account holders and (ii) certain other foreign entities, unless they certify certain information regarding their direct and indirect U.S. owners. If a payment by the Trust is subject to withholding under FATCA, the Trust is required to withhold even if such payment would otherwise be exempt from withholding under the rules applicable to foreign shareholders described above (e.g., capital gain dividends, short-term capital gain dividends, dividends attributable to qualified net interest income and dividends attributable to tax-exempt interest income). To avoid withholding, foreign financial institutions will need to either enter into agreements with the IRS that state that they will provide the IRS information, including the names, addresses and taxpayer identification numbers of direct and indirect U.S. account holders, comply with due diligence procedures with respect to the identification of U.S. accounts, report to the IRS certain information with respect to U.S. accounts maintained, agree to withhold tax on certain payments made to non-compliant foreign financial institutions or to account holders who fail to provide the required information, and determine certain other information as to their account holders or, in the event that an applicable intergovernmental agreement and implementing legislation are adopted, agree to provide certain information to other revenue authorities for transmittal to the IRS. Other foreign entities will need to either provide the name, address, and taxpayer identification number of each substantial U.S. owner or certifications of no substantial U.S. ownership unless certain exceptions apply or agree to provide certain information to other revenue authorities for transmittal to the IRS. Shareholders should consult their own tax advisors regarding the possible implications of these requirements on their investment in the Trust.

The foregoing briefly summarizes some of the important federal income tax consequences to Shareholders of investing in shares, reflects the federal tax law as of the date of this Statement of Additional Information, and does not address special tax rules applicable to certain types of investors, such as tax-exempt entities, corporate investors, foreign investors, insurance companies and financial institutions. This discussion is based upon current provisions of the Code, the

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regulations promulgated thereunder, and judicial and administrative ruling authorities, all of which are subject to change or differing interpretations by the courts or the IRS retroactively or prospectively. No attempt has been made to present a complete explanation of the federal tax treatment of the Trust or the implications to Shareholders, and the discussions here and in the prospectus are not intended as a substitute for careful tax planning. Investors should consult their tax advisors regarding other federal, state, local and, where applicable, foreign tax considerations that may be applicable in their particular circumstances, as well as any proposed tax law changes.

State and Local Taxes. Shareholders should consult their own tax advisers as to the state or local tax consequences of investing in the Trust.

OTHER INFORMATION

The Trust is an organization of the type commonly known as a “Massachusetts business trust.” Under Massachusetts law, shareholders of such a trust may, in certain circumstances, be held personally liable as partners for the obligations of the trust. The Declaration of Trust contains an express disclaimer of shareholder liability in connection with the Trust property or the acts, obligations or affairs of the Trust. The Declaration of Trust, in coordination with the Trust’s By-laws, also provides for indemnification out of the Trust property of any shareholder held personally liable for the claims and liabilities to which a shareholder may become subject by reason of being or having been a shareholder. Thus, the risk of a shareholder incurring financial loss on account of shareholder liability is limited to circumstances in which the Trust itself is unable to meet its obligations. The Trust has been advised by its counsel that the risk of any shareholder incurring any liability for the obligations of the Trust is remote.

The Declaration of Trust provides that the Trustees will not be liable for errors of judgment or mistakes of fact or law; but nothing in the Declaration of Trust protects a Trustee against any liability to the Trust or its shareholders to which he or she would otherwise be subject by reason of willful misfeasance, bad faith, gross negligence, or reckless disregard of the duties involved in the conduct of his or her office. Voting rights are not cumulative, which means that the holders of more than 50% of the shares voting for the election of Trustees can elect 100% of the Trustees and, in such event, the holders of the remaining less than 50% of the shares voting on the matter will not be able to elect any Trustees.

The Declaration of Trust provides that no person shall serve as a Trustee if shareholders holding two-thirds of the outstanding shares have removed him from that office either by a written declaration filed with the Trust’s custodian or by votes cast at a meeting called for that purpose. The Declaration of Trust further provides that the Trustees of the Trust shall promptly call a meeting of the shareholders for the purpose of voting upon a question of removal of any such Trustee or Trustees when requested in writing so to do by the record holders of not less than 10 per centum of the outstanding shares.

The Trust’s Prospectus, any related Prospectus Supplement, and this SAI do not contain all of the information set forth in the Registration Statement that the Trust has filed with the SEC. The complete Registration Statement may be obtained from the SEC upon payment of the fee prescribed by its Rules and Regulations.

CUSTODIAN

State Street Bank and Trust Company (“State Street”), State Street Financial Center, One Lincoln Street, Boston, MA 02111, is the custodian of the Trust and will maintain custody of the securities and cash of the Trust. State Street maintains the Trust’s general ledger and computes net asset value per share at least weekly. State Street also attends to details in connection with the sale, exchange, substitution, transfer and other dealings with the Trust’s investments, and receives and disburses all funds. State Street also assists in preparation of shareholder reports and the electronic filing of such reports with the SEC.

INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

[____________], independent registered public accounting firm, audits the Trust’s financial statements and provides other audit, tax and related services.

FINANCIAL STATEMENTS

The audited financial statements and the report of the independent registered public accounting firm of the Trust, for the fiscal year ended [_____], 2018, are incorporated herein by reference from the Trust’s most recent Annual Report to Common Shareholders filed with the SEC (Accession No. [________]) on Form N-CSR pursuant to Rule 30b2-1 under the 1940 Act.

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APPENDIX A

RATINGS

The ratings indicated herein are believed to be the most recent ratings available at the date of this SAI for the securities listed. Ratings are generally given to securities at the time of issuance. While the rating agencies may from time to time revise such ratings, they undertake no obligation to do so, and the ratings indicated do not necessarily represent ratings which would be given to these securities on a particular date.

MOODY’S INVESTORS SERVICE, INC. (“Moody’s”)

Ratings assigned on Moody’s global long-term and short-term rating scales are forward-looking opinions of the relative credit risks of financial obligations issued by non-financial corporates, financial institutions, structured finance vehicles, project finance vehicles, and public sector entities. Long-term ratings are assigned to issuers or obligations with an original maturity of one year or more and reflect both the likelihood of a default on contractually promised payments and the expected financial loss suffered in the event of default. Short-term ratings are assigned to obligations with an original maturity of thirteen months or less and reflect the likelihood of a default on contractually promised payments and the expected financial loss suffered in the event of a default.

GLOBAL LONG-TERM RATINGS SCALE

Aaa: Obligations rated Aaa are judged to be of the highest quality, subject to the lowest level of credit risk.

Aa: Obligations rated Aa are judged to be of high quality and are subject to very low credit risk.

A: Obligations rated A are considered upper-medium grade and are subject to low credit risk.

Baa: Obligations rated Baa are judged to be medium-grade and subject to moderate credit risk and as such may possess certain speculative characteristics

Ba: Obligations rated Ba are judged to be speculative and are subject to substantial credit risk.

B: Obligations rated B are considered speculative and are subject to high credit risk.

Caa: Obligations rated Caa are judged to be speculative of poor standing and are subject to very high credit risk.

Ca: Obligations rated Ca are highly speculative and are likely in, or very near, default, with some prospect of recovery of principal and interest.

C: Obligations rated C are the lowest rated and are typically in default, with little prospect for recovery of principal or interest.

Note: Moody’s appends numerical modifiers, 1, 2, and 3 to each generic rating classification from Aa through Caa. The modifier 1 indicates that the obligation ranks in the higher end of its generic rating category; the modifier 2 indicates a mid-range ranking; and the modifier 3 indicates a ranking in the lower end of that generic rating category.

GLOBAL SHORT-TERM RATING SCALE

Moody’s short term ratings are opinions of the ability of issuers to honor short-term financial obligations. Ratings may be assigned to issuers, short-term programs or to individual short-term debt instruments. Such obligations generally have an original maturity not exceeding thirteen months, unless explicitly noted.

P-1: Issuers (or supporting institutions) rated Prime-1 have a superior ability to repay short-term debt obligations.

P-2: Issuers (or supporting institutions) rated Prime-2 have a strong ability to repay short-term debt obligations.

P-3: Issuers (or supporting institutions) rated Prime-3 have an acceptable ability to repay short-term obligations.

NP: Issuers (or supporting institutions) rated Not Prime do not fall within any of the Prime ratings categories.

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ISSUER RATINGS

Issuer Ratings are opinions of the ability of entities to honor senior unsecured debt and debt like instruments. As such, Issuer Ratings incorporate any external support that is expected to apply to all current and future issuance of senior unsecured financial obligations and contracts, such as explicit support stemming from a guarantee of all senior unsecured financial obligations and contracts, and/or implicit support for issuers subject to joint default analysis (e.g. banks and government-related issuers). Issuer Ratings do not incorporate support arrangements, such as guarantees, that apply only to specific (but not to all) senior unsecured financial obligations and contracts.

US MUNICIPAL SHORT-TERM OBLIGATION RATINGS AND DEMAND OBLIGATION RATINGS

SHORT-TERM OBLIGATION RATINGS

While the global short-term ‘prime’ rating scale is applied to US municipal tax-exempt commercial paper, these programs are typically backed by external letters of credit or liquidity facilities and their short-term prime ratings usually map to the long-term rating of the enhancing bank or financial institution and not to the municipality’s rating. Other short-term municipal obligations, which generally have different funding sources for repayment, are rated using two additional short-term rating scales (i.e., the MIG and VMIG scales discussed below).

The Municipal Investment Grade (MIG) scale is used to rate US municipal bond anticipation notes of up to three years maturity. Municipal notes rated on the MIG scale may be secured by either pledged revenues or proceeds of a take-out financing received prior to note maturity. MIG ratings expire at the maturity of the obligation, and the issuer’s long-term rating is only one consideration in assigning the MIG rating. MIG ratings are divided into three levels—MIG 1 through MIG 3—while speculative grade short-term obligations are designated SG.

MIG 1 This designation denotes superior credit quality. Excellent protection is afforded by established cash flows, highly reliable liquidity support, or demonstrated broad-based access to the market for refinancing.

MIG 2 This designation denotes strong credit quality. Margins of protection are ample, although not as large as in the preceding group.

MIG 3 This designation denotes acceptable credit quality. Liquidity and cash-flow protection may be narrow, and market access for refinancing is likely to be less well-established.

SG This designation denotes speculative-grade credit quality. Debt instruments in this category may lack sufficient margins of protection.

Demand Obligation Ratings

In the case of variable rate demand obligations (VRDOs), a two-component rating is assigned; a long or short-term rating and demand obligation rating. The first element represents Moody’s evaluation of the degree of risk associated with scheduled principal and interest payments. The second element represents Moody’s evaluation of the degree of risk associated with the ability to receive purchase price upon demand (“demand feature”), The second element uses a rating from a variation of the MIG scale called the Variable Municipal Investment Grade (VMIG) scale. VMIG ratings of demand obligations with unconditional liquidity support are mapped from the short-term debt rating (or counterparty assessment) of the support provider, or the underlying obligor in the absence of third party liquidity support, with VMIG 1 corresponding to P-1, VMIG 2 to P-2, VMIG 3 to P-3 and SG to not prime. Transitions of VMIG ratings of demand obligations with conditional liquidity support, as shown in the diagram below, differ from transitions on the Prime scale to reflect the risk that external liquidity support will terminate if to reflect the risk that external liquidity support will terminate if the issuer’s long-term rating drops below investment grade.

VMIG 1: This designation denotes superior credit quality. Excellent protection is afforded by the superior short-term credit strength of the liquidity provider and structural and legal protections that ensure the timely payment of purchase price upon demand.

VMIG 2: This designation denotes strong credit quality. Good protection is afforded by the strong short-term credit strength of the liquidity provider and structural and legal protections that ensure the timely payment of purchase price upon demand.

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VMIG 3: This designation denotes acceptable credit quality. Adequate protection is afforded by the satisfactory short-term credit strength of the liquidity provider and structural and legal protections that ensure the timely payment of purchase price upon demand.

SG: This designation denotes speculative-grade credit quality. Demand features rated in this category may be supported by a liquidity provider that does not have an investment grade short-term rating or may lack the structural and/or legal protections necessary to ensure the timely payment of purchase price upon demand.

S&P GLOBAL RATINGS (“S&P”)

ISSUE CREDIT RATINGS DEFINITIONS

S&P’s issue credit rating is a forward-looking opinion about the creditworthiness of an obligor with respect to a specific financial obligation, a specific class of financial obligations, or a specific financial program (including ratings on medium-term note programs and commercial paper programs). It takes into consideration the creditworthiness of guarantors, insurers, or other forms of credit enhancement on the obligation and takes into account the currency in which the obligation is denominated. The opinion reflects S&P’s view of the obligor's capacity and willingness to meet its financial commitments as they come due, and may assess terms, such as collateral security and subordination, which could affect ultimate payment in the event of default.

Issue credit ratings can be either long-term or short-term. Short-term ratings are generally assigned to those obligations considered short-term in the relevant market. Short-term ratings are also used to indicate the creditworthiness of an obligor with respect to put features on long-term obligations. Medium-term notes are assigned long-term ratings.

LONG-TERM ISSUE CREDIT RATINGS:

Issue credit ratings are based, in varying degrees, on S&P’s analysis of the following considerations:

· Likelihood of payment—capacity and willingness of the obligor to meet its financial commitment on an obligation in accordance with the terms of the obligation;

· Nature of and provisions of the financial obligation and the promise that it is imputed; and

· Protection afforded by, and relative position of, the financial obligation in the event of bankruptcy, reorganization, or other arrangement under the laws of bankruptcy and other laws affecting creditors' rights.

Issue ratings are an assessment of default risk, but may incorporate an assessment of relative seniority or ultimate recovery in the event of default. Junior obligations are typically rated lower than senior obligations, to reflect the lower priority in bankruptcy, as noted above. (Such differentiation may apply when an entity has both senior and subordinated obligations, secured and unsecured obligations, or operating company and holding company obligations.)

AAA: An obligation rated ‘AAA’ has the highest rating assigned by S&P. The obligor’s capacity to meet its financial commitment on the obligation is extremely strong.

AA: An obligation rated ‘AA’ differs from the highest-rated obligors only to a small degree. The obligor’s capacity to meet its financial commitments on the obligation is very strong.

A: An obligation rated ‘A’ is somewhat more susceptible to the adverse effects of changes in circumstances and economic conditions than obligations in higher-rated categories. However, the obligor’s capacity to meet its financial commitments on the obligation is still strong.

BBB: An obligation rated ‘BBB’ exhibits adequate protection parameters. However, adverse economic conditions or changing circumstances are more likely to lead to a weakened capacity of the obligor to meet its financial commitment on the obligation.

BB, B, CCC, CC and C

Obligations rated ‘BB’, ‘B’, ‘CCC’, ‘CC’, and ‘C’ are regarded as having significant speculative characteristics. ‘BB’ indicates the least degree of speculation and ‘C’ the highest. While such obligations will likely have some quality and protective characteristics, these may be outweighed by large uncertainties or major exposures to adverse conditions.

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BB: An obligation rated ‘BB’ is less vulnerable to non-payment than other speculative issues. However, it faces major ongoing uncertainties or exposure to adverse business, financial, or economic conditions that could lead to the obligor’s inadequate capacity to meet its financial commitment on the obligation.

B: An obligation rated ‘B’ is more vulnerable to nonpayment than obligations rated ‘BB’, but the obligor currently has the capacity to meet its financial commitment on the obligation. Adverse business, financial or economic conditions will likely impair the obligor’s capacity or willingness to meet its financial commitment on the obligation.

CCC: An obligation rated ‘CCC’ is currently vulnerable to nonpayment, and is dependent upon favorable business, financial, and economic conditions for the obligor to meet its financial commitment on the obligation. In the event of adverse business, financial or, economic conditions, the obligor is not likely to have the capacity to meet its financial commitment on the obligation.

CC: An obligation rated ‘CC’ is currently highly vulnerable to nonpayment. The 'CC' rating is used when a default has not yet occurred, but S&P expects default to be a virtual certainty, regardless of the anticipated time to default.

C: An obligation rated 'C' is currently highly vulnerable to nonpayment, and the obligation is expected to have lower relative seniority or lower ultimate recovery compared to obligations that are rated higher.

D: An obligation rated 'D' is in default or in breach of an imputed promise. For non-hybrid capital instruments, the 'D' rating category is used when payments on an obligation are not made on the date due, unless S&P believes that such payments will be made within five business days in the absence of a stated grace period or within the earlier of the stated grace period or 30 calendar days. The 'D' rating also will be used upon the filing of a bankruptcy petition or the taking of similar action and where default on an obligation is a virtual certainty, for example due to automatic stay provisions. An obligation's rating is lowered to 'D' if it is subject to a distressed exchange offer.

NR: This indicates that no rating has been requested, or that there is insufficient information on which to base a rating, or that S&P does not rate a particular obligation as a matter of policy.

Plus (+) or Minus (-): The ratings from ‘AA’ to’ CCC’ may be modified by the addition of a plus (+) or minus (-) sign to show relative standing within the major rating categories.

SHORT-TERM ISSUE CREDIT RATINGS

A-1: A short-term obligation rated ‘A-1’ is rated in the highest category by S&P. The obligor’s capacity to meet its financial commitment on the obligation is strong. Within this category, certain obligations are designated with a plus sign (+). This indicates that the obligor’s capacity to meet its financial commitments on the obligation is extremely strong.

A-2: A short-term obligation rated ‘A-2’ is somewhat more susceptible to the adverse effects of changes in circumstances and economic conditions than obligations in higher rating categories. However, the obligor’s capacity to meet its financial commitment on the obligation is satisfactory.

A-3: A short-term obligation rated ‘A-3’ exhibits adequate protection parameters. However, adverse economic conditions or changing circumstances are more likely to lead to a weakened capacity of the obligor to meet its financial commitment on the obligation.

B: A short-term obligation rated ‘B’ is regarded as vulnerable and has significant speculative characteristics. The obligor currently has the capacity to meet its financial commitments; however, it faces major ongoing uncertainties which could lead to the obligor's inadequate capacity to meet its financial commitments.

C: A short-term obligation rated ‘C’ is currently vulnerable to nonpayment and is dependent upon favorable business, financial and economic conditions for the obligor to meet its financial commitment on the obligation.

D: A short-term obligation rated 'D' is in default or in breach of an imputed promise. For non-hybrid capital instruments, the 'D' rating category is used when payments on an obligation are not made on the date due, unless S&P believes that such payments will be made within any stated grace period. However, any stated grace period longer than five business days will be treated as five business days. The 'D' rating also will be used upon the filing of a bankruptcy petition or the taking of a similar action and where default on an obligation is a virtual certainty, for example due to automatic stay provisions. An obligation's rating is lowered to 'D' if it is subject to a distressed exchange offer.

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ISSUER CREDIT RATINGS DEFINITIONS

S&P’s issuer credit rating is a forward-looking opinion about an obligor's overall creditworthiness. This opinion focuses on the obligor's capacity and willingness to meet its financial commitments as they come due. It does not apply to any specific financial obligation, as it does not take into account the nature of and provisions of the obligation, its standing in bankruptcy or liquidation, statutory preferences, or the legality and enforceability of the obligation.

Counterparty credit ratings, corporate credit ratings and sovereign credit ratings are all forms of issuer credit ratings.

Issuer credit ratings can be either long-term or short-term.

LONG-TERM ISSUER CREDIT RATINGS

AAA: An obligor rated ‘AAA’ has extremely strong capacity to meet its financial commitments. ‘AAA’ is the highest issuer credit rating assigned by S&P.

AA: An obligor rated ‘AA’ has very strong capacity to meet its financial commitments. It differs from the highest-rated obligors only to a small degree.

A: An obligor rated ‘A’ has strong capacity to meet its financial commitments but is somewhat more susceptible to the adverse effects of changes in circumstances and economic conditions than obligors in higher-rated categories.

BBB: An obligor rated ‘BBB’ has adequate capacity to meet its financial commitments. However, adverse economic conditions or changing circumstances are more likely to lead to a weakened capacity of the obligor to meet its financial commitments.

BB, B, CCC and CC

Obligors rated ‘BB’, ‘B’, ‘CCC’, and ‘CC’ are regarded as having significant speculative characteristics. ‘BB’ indicates the least degree of speculation and ‘CC’ the highest. While such obligors will likely have some quality and protective characteristics, these may be outweighed by large uncertainties or major exposures to adverse conditions.

BB: An obligor ‘BB’ is less vulnerable in the near term than other lower-rated obligors. However, it faces major ongoing uncertainties and exposure to adverse business, financial, or economic conditions that could lead to the obligor’s inadequate capacity to meet its financial commitments.

B: An obligor rated ‘B’ is more vulnerable than the obligors rated ‘BB’, but the obligor currently has the capacity to meet its financial commitments. Adverse business, financial, or economic conditions will likely impair the obligor’s capacity or willingness to meets its financial commitments.

CCC: An obligor rated ‘CCC’ is currently vulnerable, and is dependent upon favorable business, financial, and economic conditions to meet its financial commitments.

CC: An obligor rated ‘CC’ is currently highly vulnerable. The 'CC' rating is used when a default has not yet occurred, but S&P expects default to be a virtual certainty, regardless of the anticipated time to default.

R: An obligor rated 'R' is under regulatory supervision owing to its financial condition. During the pendency of the regulatory supervision the regulators may have the power to favor one class of obligations over others or pay some obligations and not others.

SD and D: An obligor rated 'SD' (selective default) or 'D' is in default on one or more of its financial obligations including rated and unrated financial obligations but excluding hybrid instruments classified as regulatory capital or in non-payment according to terms. An obligor is considered in default unless S&P believes that such payments will be made within five business days of the due date in the absence of a stated grace period, or within the earlier of the stated grace period or 30 calendar days. A 'D' rating is assigned when S&P believes that the default will be a general default and that the obligor will fail to pay all or substantially all of its obligations as they come due. An 'SD' rating is assigned when S&P believes that the obligor has selectively defaulted on a specific issue or class of obligations but it will continue to meet its payment obligations on other issues or classes of obligations in a timely manner. An obligor's rating is lowered to 'D' or 'SD' if it is conducting a distressed exchange offer.

NR: An issuer designated as NR is not rated.

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Plus (+) or Minus (-): The ratings from ‘AA’ to’ CCC’ may be modified by the addition of a plus (+) or minus (-) sign to show relative standing within the major rating categories.

SHORT-TERM ISSUER CREDIT RATINGS

A-1: An obligor rated ‘A-1’ has strong capacity to meet its financial commitments. It is rated in the highest category by S&P. Within this category, certain obligors are designated with a plus sign (+). This indicates that the obligor’s capacity to meet its financial commitments is extremely strong.

A-2: An obligor rated ‘A-2’ has satisfactory capacity to meet its financial commitments. However, it is somewhat more susceptible to the adverse effects of changes in circumstances and economic conditions than obligors in the highest rating category.

A-3: An obligor rated ‘A-3’ has adequate capacity to meet its financial obligations. However, adverse economic conditions or changing circumstances are more likely to lead to a weakened capacity of the obligor to meet its financial commitments.

B: An obligor rated ‘B’ is regarded as vulnerable and has significant speculative characteristics. The obligor currently has the capacity to meet its financial commitments; however, it faces major ongoing uncertainties which could lead to the obligor’s inadequate capacity to meet its financial commitments.

C: An obligor rated 'C' is currently vulnerable to nonpayment that would result in a 'SD' or 'D' issuer rating, and is dependent upon favorable business, financial, and economic conditions for it to meet its financial commitments.

R: An obligor rated ‘R’ is under regulatory supervision owing to its financial condition. During the pendency of the regulatory supervision the regulators may have the power to favor one class of obligations over others or pay some obligations and not others.

SD and D: An obligor rated 'SD' (selective default) or 'D' has failed to pay one or more of its financial obligations (rated or unrated), excluding hybrid instruments classified as regulatory capital or in nonpayment according to terms, when it came due. An obligor is considered in default unless S&P believes that such payments will be made within any stated grace period. However, any stated grace period longer than five business days will be treated as five business days. A 'D' rating is assigned when S&P believes that the default will be a general default and that the obligor will fail to pay all or substantially all of its obligations as they come due. An 'SD' rating is assigned when S&P believes that the obligor has selectively defaulted on a specific issue or class of obligations, excluding hybrid instruments classified as regulatory capital, but it will continue to meet its payment obligations on other issues or classes of obligations in a timely manner. An obligor's rating is lowered to 'D' or 'SD' if it is conducting a distressed exchange offer.

NR: An issuer designated as NR is not rated.

MUNICIPAL SHORT-TERM NOTE RATINGS

SHORT-TERM NOTES: An S&P U.S. municipal note ratings reflects S&P opinions about the liquidity factors and market access risks unique to notes.

Notes due in three years or less will likely receive a note rating. Notes with an original maturity of more than three years will most likely receive a long-term debt rating. In determining which type of rating, if any, to assign, S&P’s analysis will review the following considerations: Amortization schedule--the larger the final maturity relative to other maturities, the more likely it will be treated as a note; and Source of payment--the more dependent the issue is on the market for its refinancing, the more likely it will be treated as a note.

Municipal Short-Term Note rating symbols are as follows:

SP-1: Strong capacity to pay principal and interest. An issue determined to possess a very strong capacity to pay debt will be given a plus (+) designation.

SP-2: Satisfactory capacity to pay principal and interest, with some vulnerability to adverse financial and economic changes over the term of the notes.

SP-3: Speculative capacity to pay principal and interest.

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FITCH RATINGS

LONG-TERM CREDIT RATINGS

Investment Grade

AAA: Highest credit quality. ‘AAA’ ratings denote the lowest expectation of credit risk. They are assigned only in case of exceptionally strong capacity for payment of financial commitments. The capacity is highly unlikely to be adversely affected by foreseeable events.

AA: Very high credit quality. ‘AA’ ratings denote expectations of very low credit risk. They indicate very strong capacity for payment of financial commitments. This capacity is not significantly vulnerable to foreseeable events.

A: High credit quality. ‘A’ ratings denote expectations of low credit risk. The capacity for payment of financial commitments is considered strong. The capacity may, nevertheless, be more vulnerable to changes in circumstances or in economic conditions that is the case for higher ratings.

BBB: Good credit quality. 'BBB' ratings indicate that expectations of default risk are currently low. The capacity for payment of financial commitments is considered adequate but adverse business or economic conditions are more likely to impair this capacity.

BB: Speculative. 'BB' ratings indicate an elevated vulnerability to default risk, particularly in the event of adverse changes in business or economic conditions over time; however, business or financial flexibility exist that supports the servicing of financial commitments.

B: Highly speculative. B' ratings indicate that material default risk is present, but a limited margin of safety remains. Financial commitments are currently being met; however, capacity for continued payment is vulnerable to deterioration in the business and economic environment.

CCC: Substantial credit risk. Default is a real possibility.

CC: Very high levels of credit risk. Default of some kind appears probable.

C: Near default. A default or default-like process has begun, or the issuer is in standstill, or for a closed funding vehicle, payment capacity is irrevocably impaired. Conditions that are indicative of a ‘C’ category rating for an issuer include:

• The issuer has entered into a grace or cure period following non-payment of a material financial obligation;

• The issuer had entered into a temporary negotiated waiver or standstill agreement following a payment default on a material financial obligation;

• The formal announcement by the issuer or their agent of distressed debt exchange;

• A closed financing vehicle where payment capacity is irrevocably impaired such that it is not expected to pay interest and/or principal in full during the life of the transaction, but where no payment default is imminent.

RD: Restricted Default. ‘RD’ ratings indicate an issuer that in Fitch’s opinion has experienced:

• An uncured payment default on a bond, loan or other material financial obligation, but

• Has not entered into bankruptcy filings, administration, receivership, liquidation, or other formal winding-up procedure, and

• Has not otherwise ceased operating.

This would include:

• The selective payment default on specific class or currency of debt;

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• The uncured expiry of any applicable grace period, cure period or default forbearance period following a payment default on a bank loan, capital markets security or other material financial obligation;

• The extension of multiple waivers of forbearance periods upon a payment default on one or more material financial obligations, either in series or in parallel; ordinary execution of a distressed debt exchange on one or more material financial obligations.

D: Default. ‘D’ ratings indicate an issuer that in Fitch’s opinion has entered into bankruptcy filings, administration, receivership, liquidation or other formal winding-up procedure or that has otherwise ceased business.

• Default ratings are not assigned prospectively to entities or their obligations; within this context, non-payment on an instrument that contains a deferral feature or grace period will generally not be considered a default until after the expiration of the deferral or grace period, unless a default is otherwise driven by bankruptcy or other similar circumstance, or by a distressed debt exchange.

• In all cases, the assignment of default rating reflects the agency’s opinion as to the most appropriate rating category consistent with the rest of its universe of ratings and may differ from the definition of default under the terms of an issuer’s financial obligations or local commercial practice.

Notes to Long-Term ratings:

The modifiers “+” or “-” may be appended to a rating to denote relative status within major rating categories. Such suffixes are not added to the ‘AAA’ Long-Term IDR category, or to Long-Term IDR categories below ‘B’.

Short-Term Credit Ratings Assigned to Obligations in Corporate, Public and Structured Finance

A short-term issuer or obligation rating is based in all cases on the short-term vulnerability to default of the rated entity or security stream and relates to the capacity to meet financial obligations in accordance with the documentation governing the relevant obligation. Short-Term Ratings are assigned to obligations whose initial maturity is viewed as “short term” based on market convention. Typically, this means up to 13 months for corporate, sovereign, and structured obligations, and up to 36 months for obligations in U.S. public finance markets.

F1: Highest short-term credit quality. Indicates the strongest intrinsic capacity for timely payment of financial commitments; may have an added “+” to denote any exceptionally strong credit feature.

F2: Good short-term credit quality. Good intrinsic capacity for timely payment of financial commitments.

F3: Fair short-term credit quality. The intrinsic capacity for timely payment of financial commitments is adequate.

B: Speculative short-term credit quality. Minimal capacity for timely payment of financial commitments, plus vulnerability to near term adverse changes in financial and economic conditions.

C: High short-term default risk. Default is a real possibility.

RD: Restricted default. Indicates an entity that has defaulted on one or more of its financial commitments, although it continues to meet other financial obligations. Typically applicable to entity ratings only.

D: Indicates a broad-based default event for an entity, or the default of a short-term obligation.

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DESCRIPTION OF INSURANCE FINANCIAL STRENGTH RATINGS

Moody’s Investors Service, Inc. Insurance Financial Strength Ratings

Moody’s Insurance Financial Strength Ratings are opinions of the ability of insurance companies to repay punctually senior policyholder claims and obligations and also reflect the expected financial loss suffered in the event of default. Specific obligations are considered unrated unless they are individually rated because the standing of a particular insurance obligation would depend on an assessment of its relative standing under those laws governing both the obligation and the insurance company.

S&P Insurer Financial Strength Ratings

An S&P insurer financial strength rating is a forward-looking opinion about the financial security characteristics of an insurance organization with respect to its ability to pay under its insurance policies and contracts in accordance with their terms. Insurer financial strength ratings are also assigned to health maintenance organizations and similar health plans with respect to their ability to pay under their policies and contracts in accordance with their terms.

This opinion is not specific to any particular policy or contract, nor does it address the suitability of a particular policy or contract for a specific purpose or purchaser. Furthermore, the opinion does not take into account deductibles, surrender or cancellation penalties, timeliness of payment, nor the likelihood of the use of a defense such as fraud to deny claims.

Insurer financial strength ratings do not refer to an organization's ability to meet nonpolicy (i.e., debt) obligations. Assignment of ratings to debt issued by insurers or to debt issues that are fully or partially supported by insurance policies, contracts, or guarantees is a separate process from the determination of insurer financial strength ratings, and follows procedures consistent with those used to assign an issue credit rating. An insurer financial strength rating is not a recommendation to purchase or discontinue any policy or contract issued by an insurer.

Long-Term Insurer Financial Strength Ratings

Category Definition

AAA

An insurer rated 'AAA' has extremely strong financial security characteristics. 'AAA' is the highest insurer financial strength rating assigned by S&P.

An insurer rated 'AA' has very strong financial security characteristics, differing only slightly from those rated higher.

An insurer rated 'A' has strong financial security characteristics, but is somewhat more likely to be affected by adverse business conditions than are insurers with higher ratings.

BBB

An insurer rated 'BBB' has good financial security characteristics, but is more likely to be affected by adverse business conditions than are higher-rated insurers.

BB; CCC; and CC

An insurer rated 'BB' or lower is regarded as having vulnerable characteristics that may outweigh its strengths. 'BB' indicates the least degree of vulnerability within the range; 'CC' the highest.

An insurer rated 'BB' has marginal financial security characteristics. Positive attributes exist, but adverse business conditions could lead to insufficient ability to meet financial commitments.

An insurer rated 'B' has weak financial security characteristics. Adverse business conditions will likely impair its ability to meet financial commitments.

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CCC

An insurer rated 'CCC' has very weak financial security characteristics, and is dependent on favorable business conditions to meet financial commitments.

An insurer rated 'CC' has extremely weak financial security characteristics and is likely not to meet some of its financial commitments.

An insurer rated 'R' is under regulatory supervision owing to its financial condition. During the pendency of the regulatory supervision, the regulators may have the power to favor one class of obligations over others or pay some obligations and not others. The rating does not apply to insurers subject only to non-financial actions such as market conduct violations.

SD or D

An insurer rated 'SD' (selective default) or 'D' is in default on one or more of its insurance policy obligations but is not under regulatory supervision that would involve a rating of 'R'. The 'D' rating also will be used upon the filing of a bankruptcy petition or the taking of similar action if payments on a policy obligation are at risk. A 'D' rating is assigned when S&P believes that the default will be a general default and that the obligor will fail to pay substantially all of its obligations in full in accordance with the policy terms. An 'SD' rating is assigned when S&P believes that the insurer has selectively defaulted on a specific class of policies but it will continue to meet its payment obligations on other classes of obligations. A selective default includes the completion of a distressed exchange offer. Claim denials due to lack of coverage or other legally permitted defenses are not considered defaults.

An insurer designated 'NR' is not rated.

Plus (+) or Minus (-): The ratings from ‘AA’ to’ CCC’ may be modified by the addition of a plus (+) or minus (-) sign to show relative standing within the major rating categories.

Fitch Insurer Financial Strength Rating

The Insurer Financial Strength (IFS) Rating provides an assessment of the financial strength of an insurance organization. The IFS Rating is assigned to the insurance company's policyholder obligations, including assumed reinsurance obligations and contract holder obligations, such as guaranteed investment contracts. The IFS Rating reflects both the ability of the insurer to meet these obligations on a timely basis, and expected recoveries received by claimants in the event the insurer stops making payments or payments are interrupted, due to either the failure of the insurer or some form of regulatory intervention. In the context of the IFS Rating, the timeliness of payments is considered relative to both contract and/or policy terms but also recognizes the possibility of reasonable delays caused by circumstances common to the insurance industry, including claims reviews, fraud investigations and coverage disputes.

The IFS Rating does not encompass policyholder obligations residing in separate accounts, unit-linked products or segregated funds, for which the policyholder bears investment or other risks. However, any guarantees provided to the policyholder with respect to such obligations are included in the IFS Rating.

Expected recoveries are based on the agency's assessments of the sufficiency of an insurance company's assets to fund policyholder obligations, in a scenario in which payments have ceased or been interrupted. Accordingly, expected recoveries exclude the impact of recoveries obtained from any government sponsored guaranty or policyholder protection funds. Expected recoveries also exclude the impact of collateralization or security, such as letters of credit or trusteed assets, supporting select reinsurance obligations.

IFS Ratings can be assigned to insurance and reinsurance companies in any insurance sector, including the life & annuity, non-life, property/casualty, health, mortgage, financial guaranty, residual value and title insurance sectors, as well as to managed care companies such as health maintenance organizations.

The IFS Rating does not address the quality of an insurer's claims handling services or the relative value of products sold.

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The IFS Rating uses the same symbols used by the agency for its International and National credit ratings of long-term or short-term debt issues. However, the definitions associated with the ratings reflect the unique aspects of the IFS Rating within an insurance industry context.

Obligations for which a payment interruption has occurred due to either the insolvency or failure of the insurer or some form of regulatory intervention will generally be rated between 'B' and 'C' on the Long-Term IFS Rating scales (both International and National). International Short-Term IFS Ratings assigned under the same circumstances will align with the insurer's International Long-Term IFS Ratings.

Eaton Vance Senior Income Trust

SAI dated [_____], 2018

APPENDIX B

Eaton Vance Funds

Proxy Voting Policy and Procedures

I. Overview

The Boards of Trustees (the “Board”) of the Eaton Vance Funds¹ have determined that it is in the interests of the Funds’ shareholders to adopt these written proxy voting policy and procedures (the “Policy”). For purposes of this Policy:

“Fund” means each registered investment company sponsored by the Eaton Vance organization; and

“Adviser” means the adviser or sub-adviser responsible for the day-to-day management of all or a portion of the Fund’s assets.

II. Delegation of Proxy Voting Responsibilities

The Board hereby delegates to the Adviser responsibility for voting the Fund’s proxies as described in this Policy. In this connection, the Adviser is required to provide the Board with a copy of its proxy voting policies and procedures (“Adviser Procedures”) and all Fund proxies will be voted in accordance with the Adviser Procedures, provided that in the event a material conflict of interest arises with respect to a proxy to be voted for the Fund (as described in Section IV below) the Adviser shall follow the process for voting such proxy as described in Section IV below.

The Adviser is required to report any material change to the Adviser Procedures to the Board in the manner set forth in Section V below. In addition, the Board will review the Adviser Procedures annually.

III. Delegation of Proxy Voting Disclosure Responsibilities

Pursuant to Rule 30b1-4 promulgated under the Investment Company Act of 1940, as amended (the “1940 Act”), the Fund is required to file Form N-PX no later than August 31st of each year. On Form N-PX, the Fund is required to disclose, among other things, information concerning proxies relating to the Fund’s portfolio investments, whether or not the Fund (or its Adviser) voted the proxies relating to securities held by the Fund and how it voted on the matter and whether it voted for or against management.

To facilitate the filing of Form N-PX for the Fund:

The Adviser is required to record, compile and transmit in a timely manner all data required to be filed on Form N-PX for the Fund that it manages. Such data shall be transmitted to Eaton Vance Management, which acts as administrator to the Fund (the “Administrator”) or the third party service provider designated by the Administrator; and

the Administrator is required to file Form N-PX on behalf of the Fund with the Securities and Exchange Commission (“Commission”) as required by the 1940 Act. The Administrator may delegate the filing to a third party service party provided each such filing is reviewed and approved by the Administrator.

IV. Conflicts of Interest

The Board expects the Adviser, as a fiduciary to the Fund it manages, to put the interests of the Fund and its shareholders above those of the Adviser. When required to vote a proxy for the Fund, the Adviser may have material business relationships with the issuer soliciting the proxy that could give rise to a potential material conflict of interest for the Adviser.² In the event such a material conflict of interest arises, the Adviser, to the extent it is aware or reasonably should have been aware of the material conflict, will refrain from voting any proxies related to companies giving rise to such material conflict until it notifies and consults with the appropriate Board, or any committee, sub-committee or group of Independent Trustees identified by the Board (as long as such committee, sub-committee or group contains at least two or more Independent Trustees) (the “Board Members”), concerning the material conflict.³ For ease of communicating with the Board Members, the Adviser is required to provide the foregoing notice to the Fund’s Chief Legal Officer who will then notify and facilitate a consultation with the Board Members.

Once the Board Members have been notified of the material conflict:

They shall convene a meeting to review and consider all relevant materials related to the proxies involved. This meeting shall be convened within 3 business days, provided that it an effort will be made to convene the meeting sooner if the proxy must be voted in less than 3 business days;

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In considering such proxies, the Adviser shall make available all materials requested by the Board Members and make reasonably available appropriate personnel to discuss the matter upon request.

The Board Members will then instruct the Adviser on the appropriate course of action with respect to the proxy at issue.

If the Board Members are unable to meet and the failure to vote a proxy would have a material adverse impact on the Fund(s) involved, the Adviser will have the right to vote such proxy, provided that it discloses the existence of the material conflict to the Chairperson of the Board as soon as practicable and to the Board at its next meeting. Any determination regarding the voting of proxies of the Fund that is made by the Board Members shall be deemed to be a good faith determination regarding the voting of proxies by the full Board.

V. Reports and Review

The Administrator shall make copies of each Form N-PX filed on behalf of the Fund available for the Boards’ review upon the Boards’ request. The Administrator (with input from the Adviser for the Fund) shall also provide any reports reasonably requested by the Board regarding the proxy voting records of the Fund.

The Adviser shall report any material changes to the Adviser Procedures to the Board as soon as practicable and the Boards will review the Adviser Procedures annually.

The Adviser also shall report any changes to the Adviser Procedures to the Fund Chief Legal Officer prior to implementing such changes in order to enable the Administrator to effectively coordinate the Fund’s disclosure relating to the Adviser Procedures.

To the extent requested by the Commission, the Policy and the Adviser Procedures shall be appended to the Fund’s statement of additional information included in its registration statement.

_____________________

The Eaton Vance Funds may be organized as trusts or corporations. For ease of reference, the Funds may be referred to herein as Trusts and the Funds’ Board of Trustees or Board of Directors may be referred to collectively herein as the Board.

An Adviser is expected to maintain a process for identifying a potential material conflict of interest. As an example only, such potential conflicts may arise when the issuer is a client of the Adviser and generates a significant amount of fees to the Adviser or the issuer is a distributor of the Adviser’s products.

If a material conflict of interest exists with respect to a particular proxy and the proxy voting procedures of the relevant Adviser require that proxies are to be voted in accordance with the recommendation of a third party proxy voting vendor, the requirements of this Section IV shall only apply if the Adviser intends to vote such proxy in a manner inconsistent with such third party recommendation.

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EATON VANCE MANAGEMENT

BOSTON MANAGEMENT AND RESEARCH

EATON VANCE INVESTMENT COUNSEL

EATON VANCE TRUST COMPANY

EATON VANCE MANAGEMENT (INTERNATIONAL) LIMITED

EATON VANCE ADVISERS INTERNATIONAL LTD.

PROXY VOTING POLICIES AND PROCEDURES

I. Introduction

Eaton Vance Management, Boston Management and Research, Eaton Vance Investment Counsel, Eaton Vance Management (International) Limited, Eaton Vance Advisers International Ltd. and Eaton Vance Trust Company (each an “Adviser” and collectively the “Advisers”) have each adopted and implemented policies and procedures that each Adviser believes are reasonably designed to ensure that proxies are voted in the best interest of clients, in accordance with its fiduciary duties and, to the extent applicable, Rule 206(4)-6 under the Investment Advisers Act of 1940, as amended. The Advisers’ authority to vote the proxies of their clients is established by their advisory contracts or similar documentation, such as the Eaton Vance Funds Proxy Voting Policy and Procedures. These proxy policies and procedures reflect the U.S. Securities and Exchange Commission (“SEC”) requirements governing advisers and the long-standing fiduciary standards and responsibilities for ERISA accounts set out in the Department of Labor Bulletin 94-2 C.F.R. 2509.94-2 (July 29, 1994).

II. Overview

Each Adviser manages its clients’ assets with the overriding goal of seeking to provide the greatest possible return to such clients consistent with governing laws and the investment policies of each client. In pursuing that goal, each Adviser seeks to exercise its clients’ rights as shareholders of voting securities to support sound corporate governance of the companies issuing those securities with the principle aim of maintaining or enhancing the companies’ economic value.

The exercise of shareholder rights is generally done by casting votes by proxy at shareholder meetings on matters submitted to shareholders for approval (for example, the election of directors or the approval of a company’s stock option plans for directors, officers or employees). Each Adviser has established guidelines (“Guidelines”) as described below and generally will utilize such Guidelines in voting proxies on behalf of its clients. The Guidelines are largely based on those developed by the Agent (defined below) but also reflect input from the Global Proxy Group (defined below) and other Adviser investment professionals and are believed to be consistent with the views of the Adviser on the various types of proxy proposals. These Guidelines are designed to promote accountability of a company’s management and board of directors to its shareholders and to align the interests of management with those of shareholders. The Guidelines provide a framework for analysis and decision making but do not address all potential issues.

Except as noted below, each Adviser will vote any proxies received by a client for which it has sole investment discretion through a third-party proxy voting service (“Agent”) in accordance with the Guidelines in a manner that is reasonably designed to eliminate any potential conflicts of interest, as described more fully below. The Agent is currently Institutional Shareholder Services Inc. Where applicable, proxies will be voted in accordance with client-specific guidelines or, in the case of an Eaton Vance Fund that is sub-advised, pursuant to the sub-adviser’s proxy voting policies and procedures. Although an Adviser retains the services of the Agent for research and voting recommendations, the Adviser remains responsible for proxy voting decisions.

III. Roles and Responsibilities

A. Proxy Administrator

The Proxy Administrator and/or her designee coordinate the consideration of proxies referred back to the Adviser by the Agent, and otherwise administers these Procedures. In the Proxy Administrator’s absence, another employee of the Adviser may perform the Proxy Administrator’s responsibilities as deemed appropriate by the Global Proxy Group. The Proxy Administrator also may designate another employee to perform certain of the Proxy Administrator’s duties hereunder, subject to the oversight of the Proxy Administrator.

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B. Agent

The Agent is responsible for coordinating with the clients’ custodians and the Advisers to ensure that all proxy materials received by the custodians relating to the portfolio securities are processed in a timely fashion. Each Adviser shall instruct the custodian for its clients to deliver proxy ballots and related materials to the Agent. The Agent shall vote and/or refer all proxies in accordance with the Guidelines. The Agent shall retain a record of all proxy votes handled by the Agent. With respect to each Eaton Vance Fund memorialized therein, such record must reflect all of the information required to be disclosed in the Fund’s Form N-PX pursuant to Rule 30b1-4 under the Investment Company Act of 1940, to the extent applicable. In addition, the Agent is responsible for maintaining copies of all proxy statements received by issuers and to promptly provide such materials to an Adviser upon request.

Subject to the oversight of the Advisers, the Agent shall establish and maintain adequate internal controls and policies in connection with the provision of proxy voting services to the Advisers, including methods to reasonably ensure that its analysis and recommendations are not influenced by a conflict of interest, and shall disclose such controls and policies to the Advisers when and as provided for herein. Unless otherwise specified, references herein to recommendations of the Agent shall refer to those in which no conflict of interest has been identified. The Advisers are responsible for the ongoing oversight of the Agent as contemplated by SEC Staff Legal Bulletin No. 20 (June 30, 2014). Such oversight currently may include one or more of the following:

periodic review of Agent’s proxy voting platform and reporting capabilities (including recordkeeping);

periodic review of a sample of ballots for accuracy and correct application of the Guidelines;

periodic meetings with Agent’s client services team;

periodic in-person and/or web-based due diligence meetings;

receipt and review of annual certifications received from the Agent; and/or

annual review of due diligence materials provided by the Agent, including review of procedures and practices regarding potential conflicts of interests.

C. Global Proxy Group

The Adviser shall establish a Global Proxy Group which is responsible for establishing the Guidelines (described below) and reviewing such Guidelines at least annually. The Global Proxy Group shall also review recommendations to vote proxies in a manner that is contrary to the Guidelines and when the proxy relates to a conflicted company of the Adviser or the Agent as described below.

The members of the Global Proxy Group shall include the Chief Equity Investment Officer of Eaton Vance Management (“EVM”) and selected members of the Equity Departments of EVM and Eaton Vance Advisers International Ltd. (“EVAIL”) and EVM’s Global Income Department. The Proxy Administrator is not a voting member of the Global Proxy Group. Members of the Global Proxy Group may be changed from time to time at the Advisers’ discretion. Matters that require the approval of the Global Proxy Group may be acted upon by its member(s) available to consider the matter.

IV. Proxy Voting

A. The Guidelines

The Global Proxy Group shall establish recommendations for the manner in which proxy proposals shall be voted (the “Guidelines”). The Guidelines shall identify when ballots for specific types of proxy proposals shall be voted⁽¹⁾or referred to the Adviser. The Guidelines shall address a wide variety of individual topics, including, among other matters, shareholder voting rights, anti-takeover defenses, board structures, the election of directors, executive and director compensation, reorganizations, mergers, issues of corporate social responsibility and other proposals affecting shareholder rights. In determining the Guidelines, the Global Proxy Group considers the recommendations of the Agent as well as input from the Advisers’ portfolio managers and analysts and/or other internally developed or third party research.

The Global Proxy Group shall review the Guidelines at least annually and, in connection with proxies to be voted on behalf of the Eaton Vance Funds, the Adviser will submit amendments to the Guidelines to the Fund Boards each year for approval.

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With respect to the types of proxy proposals listed below, the Guidelines will generally provide as follows:

1. Proposals Regarding Mergers and Corporate Restructurings/Disposition of Assets/Termination/Liquidation and Mergers

The Agent shall be directed to refer proxy proposals accompanied by its written analysis and voting recommendation to the Proxy Administrator and/or her designee for all proposals relating to Mergers and Corporate Restructurings.

2. Corporate Structure Matters/Anti-Takeover Defenses

As a general matter, the Advisers will normally vote against anti-takeover measures and other proposals designed to limit the ability of shareholders to act on possible transactions (except in the case of closed-end management investment companies).

3. Proposals Regarding Proxy Contests

The Agent shall be directed to refer contested proxy proposals accompanied by its written analysis and voting recommendation to the Proxy Administrator and/or her designee.

4. Social and Environmental Issues

The Advisers will vote social and environmental proposals on a “case-by-case” basis taking into consideration industry best practices and existing management policies and practices.

Interpretation and application of the Guidelines is not intended to supersede any law, regulation, binding agreement or other legal requirement to which an issuer or the Adviser may be or become subject. The Guidelines generally relate to the types of proposals that are most frequently presented in proxy statements to shareholders. In certain circumstances, an Adviser may determine to vote contrary to the Guidelines subject to the voting procedures set forth below.

B. Voting Procedures

Except as noted in Section V below, the Proxy Administrator and/or her designee shall instruct the Agent to vote proxies as follows:

1. Vote in Accordance with Guidelines

If the Guidelines prescribe the manner in which the proxy is to be voted, the Agent shall vote in accordance with the Guidelines, which for certain types of proposals, are recommendations of the Agent made on a case-by-case basis.

2. Seek Guidance for a Referred Item or a Proposal for which there is No Guideline

If (i) the Guidelines state that the proxy shall be referred to the Adviser to determine the manner in which it should be voted or (ii) a proxy is received for a proposal for which there is no Guideline, the Proxy Administrator and/or her designee shall consult with the analyst(s) covering the company subject to the proxy proposal and shall instruct the Agent to vote in accordance with the determination of the analyst. The Proxy Administrator and/or her designee will maintain a record of all proxy proposals that are referred by the Agent, as well as all applicable recommendations, analysis and research received and the resolution of the matter. Where more than one analyst covers a particular company and the recommendations of such analysts for voting a proposal subject to this Section IV.B.2 conflict, the Global Proxy Group shall review such recommendations and any other available information related to the proposal and determine the manner in which it should be voted, which may result in different recommendations for clients (including Funds).

3. Votes Contrary to the Guidelines or Where Agent is Conflicted

In the event an analyst with respect to companies within his or her coverage area may recommend a vote contrary to the Guidelines, the Proxy Administrator and/or her designee will provide the Global Proxy Group with the Agent’s recommendation for the Proposal along with any other relevant materials, including a description of the basis for the analyst’s recommendation via email and the Proxy Administrator and/or designee will then instruct the Agent to vote the proxy in the manner determined by the Global Proxy Group. Should the vote by the Global Proxy Group concerning one or more recommendations result in a tie, EVM’s Chief Equity Investment Officer will determine the manner in which the proxy will be voted. The Adviser will provide a report to the Boards of Trustees of the Eaton Vance Funds reflecting any votes cast on behalf of the Eaton Vance Funds contrary to the Guidelines, and shall do so quarterly. A similar process will be followed if the Agent has a conflict of interest with respect to a proxy as described in Section VI.B.

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4. Do Not Cast a Vote

It shall generally be the policy of the Advisers to take no action on a proxy for which no client holds a position or otherwise maintains an economic interest in the relevant security at the time the vote is to be cast. In addition, the Advisers may determine not to vote (i) if the economic effect on shareholders' interests or the value of the portfolio holding is indeterminable or insignificant (e.g., proxies in connection with securities no longer held in the portfolio of a client or proxies being considered on behalf of a client that is no longer in existence); (ii) if the cost of voting a proxy outweighs the benefits (e.g., certain international proxies, particularly in cases in which share blocking practices may impose trading restrictions on the relevant portfolio security); or (iii) in markets in which shareholders' rights are limited, and the Adviser is unable to timely access ballots or other proxy information. Non-Votes may also result in certain cases in which the Agent's recommendation has been deemed to be conflicted, as provided for herein.

C. Securities on Loan

When a fund client participates in the lending of its securities and the securities are on loan at the record date for a shareholder meeting, proxies related to such securities generally will not be forwarded to the relevant Adviser by the fund’s custodian and therefore will not be voted. In the event that the Adviser determines that the matters involved would have a material effect on the applicable fund’s investment in the loaned securities, the Adviser will make reasonable efforts to terminate the loan in time to be able to cast such vote or exercise such consent. The Adviser shall instruct the fund’s security lending agent to refrain from lending the full position of any security held by a fund to ensure that the Adviser receives notice of proxy proposals impacting the loaned security.

V. Recordkeeping

The Advisers will maintain records relating to the proxies they vote on behalf of their clients in accordance with Section 204-2 of the Investment Advisers Act of 1940, as amended. Those records will include:

A copy of the Advisers’ proxy voting policies and procedures;

Proxy statements received regarding client securities. Such proxy statements received from issuers are either in the SEC’s EDGAR database or are kept by the Agent and are available upon request;

A record of each vote cast;

A copy of any document created by the Advisers that was material to making a decision on how to vote a proxy for a client or that memorializes the basis for such a decision; and

Each written client request for proxy voting records and the Advisers’ written response to any client request (whether written or oral) for such records.

All records described above will be maintained in an easily accessible place for five years and will be maintained in the offices of the Advisers or their Agent for two years after they are created.

Notwithstanding anything contained in this Section V, Eaton Vance Trust Company shall maintain records relating to the proxies it votes on behalf of its clients in accordance with laws and regulations applicable to it and its activities. In addition, EVAIL shall maintain records relating to the proxies it votes on behalf of its clients in accordance with UK law.

VI. Assessment of Agent and Identification and Resolution of Conflicts with Clients

A. Assessment of Agent

The Advisers shall establish that the Agent (i) is independent from the Advisers, (ii) has resources that indicate it can competently provide analysis of proxy issues, and (iii) can make recommendations in an impartial manner and in the best interests of the clients and, where applicable, their beneficial owners. The Advisers shall utilize, and the Agent shall comply with, such methods for establishing the foregoing as the Advisers may deem reasonably appropriate and shall do so not less than annually as well as prior to engaging the services of any new proxy voting service. The Agent shall also notify the Advisers in writing within fifteen (15) calendar days of any material change to information previously provided to an Adviser in connection with establishing the Agent’s independence, competence or impartiality.

B. Conflicts of Interest

As fiduciaries to their clients, each Adviser puts the interests of its clients ahead of its own. In order to ensure that relevant personnel of the Advisers are able to identify potential material conflicts of interest, each Adviser will take the following steps:

Eaton Vance Senior Income Trust

SAI dated [_____], 2018

Quarterly, the Eaton Vance Legal and Compliance Department will seek information from the department heads of each department of the Advisers and of Eaton Vance Distributors, Inc. (“EVD”) (an affiliate of the Advisers and principal underwriter of certain Eaton Vance Funds). Each department head will be asked to provide a list of significant clients or prospective clients of the Advisers or EVD.

A representative of the Legal and Compliance Department will compile a list of the companies identified (the “Conflicted Companies”) and provide that list to the Proxy Administrator.

The Proxy Administrator will compare the list of Conflicted Companies with the names of companies for which he or she has been referred a proxy statement (the “Proxy Companies”). If a Conflicted Company is also a Proxy Company, the Proxy Administrator will report that fact to the Global Proxy Group.

If the Proxy Administrator expects to instruct the Agent to vote the proxy of the Conflicted Company strictly according to the Guidelines contained in these Proxy Voting Policies and Procedures (the “Policies”) or the recommendation of the Agent, as applicable, he or she will (i) inform the Global Proxy Group of that fact, (ii) instruct the Agent to vote the proxies and (iii) record the existence of the material conflict and the resolution of the matter.

If the Proxy Administrator intends to instruct the Agent to vote in a manner inconsistent with the Guidelines, the Global Proxy Group will then determine if a material conflict of interest exists between the relevant Adviser and its clients (in consultation with the Legal and Compliance Department if needed). If the Global Proxy Group determines that a material conflict exists, prior to instructing the Agent to vote any proxies relating to these Conflicted Companies the Adviser will seek instruction on how the proxy should be voted from:

The client, in the case of an individual, corporate, institutional or benefit plan client;

In the case of a Fund, its board of directors, any committee, sub-committee or group of Independent Trustees (as long as such committee, sub-committee or group contains at least two or more Independent Trustees); or

The adviser, in situations where the Adviser acts as a sub-adviser to such adviser.

The Adviser will provide all reasonable assistance to each party to enable such party to make an informed decision.

If the client, Fund board or adviser, as the case may be, fails to instruct the Adviser on how to vote the proxy, the Adviser will generally instruct the Agent, through the Proxy Administrator, to abstain from voting in order to avoid the appearance of impropriety. If however, the failure of the Adviser to vote its clients’ proxies would have a material adverse economic impact on the Advisers’ clients’ securities holdings in the Conflicted Company, the Adviser may instruct the Agent, through the Proxy Administrator, to vote such proxies in order to protect its clients’ interests. In either case, the Proxy Administrator will record the existence of the material conflict and the resolution of the matter.

The Advisers shall also identify and address conflicts that may arise from time to time concerning the Agent. Upon the Advisers’ request, which shall be not less than annually, and within fifteen (15) calendar days of any material change to such information previously provided to an Adviser, the Agent shall provide the Advisers with such information as the Advisers deem reasonable and appropriate for use in determining material relationships of the Agent that may pose a conflict of interest with respect to the Agent’s proxy analysis or recommendations. Such information shall include, but is not limited to, a monthly report from the Agent detailing the Agent’s Corporate Securities Division clients and related revenue data. The Advisers shall review such information on a monthly basis. The Proxy Administrator shall instruct the Agent to refer any proxies for which a material conflict of the Agent is deemed to be present to the Proxy Administrator. Any such proxy referred by the Agent shall be referred to the Global Proxy Group for consideration accompanied by the Agent’s written analysis and voting recommendation. The Proxy Administrator will instruct the Agent to vote the proxy as recommended by the Global Proxy Group.

⁽¹⁾

The Guidelines will prescribe how a proposal shall be voted or provide factors to be considered on a case-by-case basis by the Agent in recommending a vote pursuant to the Guidelines.

Eaton Vance Senior Income Trust

SAI dated [_____], 2018

Eaton Vance Senior Income Trust

Statement of Additional Information

[_____], 2018

_______________

Investment Adviser and Administrator

Eaton Vance Management

Two International Place

Boston, MA 02110

Custodian

State Street Bank and Trust Company

State Street Financial Center, One Lincoln Street

Boston, MA 02111

Transfer Agent

American Stock Transfer & Trust Company, LLC

6201 15^th Avenue

Brooklyn, NY 11219

Independent Registered Public Accounting Firm

[_________]

Eaton Vance Senior Income Trust

SAI dated [_____], 2018

PART C

OTHER INFORMATION

ITEM 25.

FINANCIAL STATEMENTS AND EXHIBITS

(1) FINANCIAL STATEMENTS:

Included in Part A:

Financial Highlights.

Included in Part B:

Registrant’s Certified Shareholder Report on Form N-CSR filed [_________] (Accession No. [________]) and incorporated herein by reference.

_______________________________

(2) EXHIBITS:

(a)	(1)	Agreement and Declaration of Trust dated September 23, 1998 filed as Exhibit (a) is incorporated herein by reference to the Registration Statement under the Securities Act of 1933 (1933 Act File No. 333-64151) and under the Investment Company Act of 1940 (1940 Act File No. 811-09013) filed with the Commission on September 24, 1998 (Accession No. 0000898432-98-000638) (“Registration Statement”).
	(2)	Amendment dated August 11, 2008 to Agreement and Declaration of Trust is incorporated herein by reference to the Registrant’s initial Registration Statement on Form N-2 (File Nos. 333-175096 and 811-09013) as to Registrant’s shelf offering filed with the Commission on June 23, 2011 (Accession No. 0000898432-11-000792) (“Initial Shelf Registration Statement”).
(b)	(1)	By-Laws filed as Exhibit (b) is incorporated herein by reference to the Registrant’s Registration Statement.
	(2)	Amended By-Laws filed as Exhibit (b) to Pre-Effective Amendment No. 1 to the Registration Statement under the Securities Act of 1933 (1933 Act File No. 333-64151) and Amendment No. 1 to the Registration Statement under the Investment Company Act of 1940 (1940 Act File No. 811-09013) filed with the Commission on October 27, 1998 (Accession No. 0000950135-98-005546) (“Amendment No. 1”).
	(3)	Second Amended By-Laws filed as Exhibit (b)(2) to Pre-Effective Amendment No. 1 to the Registration Statement under the Securities Act of 1933 (1933 Act File No. 333-58758) and Amendment No. 4 to the Registration Statement under the Investment Company Act of 1940 (1940 Act File No. 811-09013) filed with the Commission on June 19, 2001 (Accession No. 0000940394-01-500292) (“Amendment No. 4”) and incorporated herein by reference.
	(4)	Amendment to By-Laws effective February 7, 2005 is incorporated herein by reference to the Initial Shelf Registration Statement.
	(5)	Amendment to By-Laws effective December 11, 2006 is incorporated herein by reference to the Initial Shelf Registration Statement.
	(6)	Amendment to By-Laws effective August 11, 2008 is incorporated herein by reference to the Initial Shelf Registration Statement.
	(7)	Amendment to By-Laws effective April 23, 2012 is incorporated herein by reference to Pre-Effective Amendment No. 1 to the Initial Shelf Registration Statement under the Securities Act of 1933 (1933 Act File No. 333-175096) and Amendment No. 7 to the Registration Statement under the Investment Company Act of 1940 (1940 Act File No. 811-09013) as to the Registrant’s shelf offering filed with the Commission on September 28, 2012 (Accession No. 0000898432-12-001078) (“Pre-Effective Amendment No. 1 to the Initial Shelf Registration Statement”).

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(c)		Not applicable.
(d)	(1)	Form of Specimen Certificate representing the Registrant's Common Shares of Beneficial Interest filed as Exhibit (d) is incorporated herein by reference to the Registrant’s Registration Statement.
	(2)	Form of Specimen Certificate representing the Registrant's Auction Preferred Shares of Beneficial Interest filed as Exhibit (d)(2) to Amendment No. 4 and incorporated herein by reference.
(e)		Dividend Reinvestment Plan filed as Exhibit (e) is incorporated herein by reference to the Registrant’s Registration Statement.
(f)		Not applicable.
(g)	(1)	Investment Advisory Agreement dated October 19, 1998 filed as Exhibit (g) to Amendment No. 1 and incorporated herein by reference.
	(2)	Fee Reduction Agreement dated April 26, 2010 is incorporated herein by reference to the Initial Shelf Registration Statement.
(h)	(1)	Form of Underwriting Agreement dated October 27, 1998 filed as Exhibit (h)(1) to Amendment No. 1 and incorporated herein by reference.
	(2)	Amended and Restated Master Agreement Among Underwriters filed as Exhibit (h)(2) to Amendment No. 1 and incorporated herein by reference.
	(3)	Amended and Restated Master Selected Dealer Agreement filed as Exhibit (h)(3) to Amendment No. 1 and incorporated herein by reference.
	(4)	Form of Underwriting Agreement for Auction Preferred Shares filed as Exhibit (h) to Pre-Effective Amendment No. 2 to the Registration Statement under the Securities Act of 1933 (1933 Act File No. 333-58758) and Amendment No. 5 to the Registration Statement under the Investment Company Act of 1940 (1940 Act File No. 811-09013) filed with the Commission on June 19, 2001 (Accession No. 0000940394-01-500302) ("Amendment No. 5") and incorporated herein by reference.
	(5)	Form of Distribution Agreement with respect to the Rule 415 shelf offering to be filed by pre-effective amendment.
	(6)	Form of Sub-Placement Agent Agreement to be filed by pre-effective amendment.
(i)		The Securities and Exchange Commission has granted the Registrant an exemptive order that permits the Registrant to enter into deferred compensation arrangements with its independent Trustees. See in the matter of Capital Exchange Fund, Inc., Release No. IC- 20671 (November 1, 1994).
(j)	(1)	Amended and Restated Master Custodian Agreement between Eaton Vance Funds and State Street Bank & Trust Company dated September 1, 2013 filed as Exhibit (g)(1) to Post-Effective Amendment No. 211 of Eaton Vance Mutual Funds Trust (File Nos. 002-90946, 811-04015) filed September 24, 2013 (Accession No. 0000940394-13-001073) and incorporated herein by reference.
	(2)	Amended and Restated Services Agreement with State Street Bank & Trust Company dated September 1, 2010 filed as exhibit (g)(2) to Post-Effective Amendment No. 108 of Eaton Vance Special Investment Trust (File Nos. 02-27962, 811-1545) filed September 27, 2010 (Accession No. 0000940394-10-001000) and incorporated herein by reference.

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	(3)	Amendment Number 1 dated May 16, 2012 to Amended and Restated Services Agreement with State Street Bank & Trust Company dated September 1, 2010 filed as Exhibit (g)(3) to Post-Effective Amendment No. 39 of Eaton Vance Municipals Trust II (File Nos. 033-71320, 811-08134) filed May 29, 2012 (Accession No. 0000940394-12-000641) and incorporated herein by reference.
	(4)	Amendment dated September 1, 2013 to Amended and Restated Services Agreement with State Street Bank & Trust Company filed as Exhibit (g)(4) to Post-Effective Amendment No. 211 of Eaton Vance Mutual Funds Trust (File Nos. 002-90946, 811-04015) filed September 24, 2013 (Accession No. 0000940394-13-001073) and incorporated herein by reference.
(k)	(1)	Transfer Agency and Services Agreement dated February 5, 2007 between American Stock Transfer & Trust Company and each Registered Investment Company listed on Exhibit 1 filed as Exhibit (k)(1) is incorporated herein by reference to Pre-Effective Amendment No. 3 to the initial Registration Statement on Form N-2 of Eaton Vance Tax-Managed Global Diversified Equity Income Fund (File Nos. 333-138318, 811-21973) filed February 21, 2007 (Accession No. 0000950135- 07- 000974).
	(2)	Amendment dated April 21, 2008 to Transfer Agency and Services Agreement dated February 5, 2007 between American Stock Transfer & Trust Company and each Registered Investment Company listed on Exhibit 1 filed as Exhibit (k)(1) is incorporated herein by reference to Pre-Effective Amendment No. 1 to the initial Registration Statement on Form N-2 of Eaton Vance National Municipal Opportunities Trust (File Nos. 333-156948, 811-22269) filed April 21, 2009 (Accession No. 0000950135- 09- 083055).
	(3)	Amendment dated June 13, 2012 to Transfer Agency and Services Agreement dated February 5, 2007 between American Stock Transfer & Trust Company and each Registered Investment Company listed on Exhibit 1 filed as Exhibit (k)(1) is incorporated herein by reference to Pre-Effective Amendment No. 2 to the initial Registration Statement on Form N-2 of Eaton Vance High Income 2021 Target Term Trust (File Nos. 333-209436, 811-23136) filed April 25, 2016 (Accession No. 0000950135- 16- 552383).
	(4)	Amended and Restated Administrative Services Agreement dated August 6, 2012 filed as Exhibit (k)(2) to Post-Effective Amendment No. 3 filed October 27, 2014 (Accession No. 0000940394-14-001403) and incorporated herein by reference.
	(3)	Shareholder Servicing Agreement dated as of October 19, 1998 filed as Exhibit (k)(3) to Amendment No. 1 and incorporated herein by reference.
	(4)	Form of Auction Agency Agreement to the Auction Preferred Shares filed as Exhibit (k)(1) to Amendment No. 5 and incorporated herein by reference.
	(5)	Form of Broker-Dealer Agreement as to the Registrant's Auction Preferred Shares filed as Exhibit (k)(2) to Amendment No. 5 and incorporated herein by reference.
	(6)	Form of DTC Representations Letter as to the Registrant's Auction Preferred Shares filed as Exhibit (k)(3) to Amendment No. 5 and incorporated herein by reference.
(l)		Opinion of Internal Counsel to be filed by pre-effective amendment.
(m)		Not applicable.
(n)		Consent of Independent Registered Public Accounting Firm to be filed by pre-effective amendment.
(o)		Not applicable.
(p)		Letter Agreement with Eaton Vance Management dated October 23, 1998 filed as Exhibit (p) to Amendment No. 1 and incorporated herein by reference.

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	(q)			Not applicable.
	(r)			Codes of Ethics adopted by the Eaton Vance Funds and the Eaton Vance Entities effective October 1, 2018 filed as Exhibit (p)(1) to Post-Effective Amendment No. 304 of Eaton Vance Mutual Funds Trust (File Nos. 002-90946, 811-04015) filed October 17, 2018 (Accession No. 0000940394-18-001695) and incorporated herein by reference.
	(s)			Power of Attorney dated October 10, 2018 filed as Exhibit (s) to the Registrant’s Post-Effective Amendment No. 3 on Form N-2 filed October 24, 2018 (Accession No. 0000940394-18-XXXXXXX) and incorporated herein by reference.

ITEM 26.

MARKETING ARRANGEMENTS

See Form of Distribution Agreement with respect to the Rule 415 shelf offering to be filed by pre-effective amendment.

See Form of Sub-Placement Agent Agreement to be filed by pre-effective amendment.

ITEM 27.

OTHER EXPENSES OF ISSUANCE AND DISTRIBUTION

The approximate expenses in connection with the offering are as follows:

Registration and Filing Fees
FINRA Fees
New York Stock Exchange Fees
Costs of Printing and Engraving
Accounting Fees and Expenses
Legal Fees and Expenses
Total

ITEM 28.

PERSONS CONTROLLED BY OR UNDER COMMON CONTROL

None.

ITEM 29.

NUMBER OF HOLDERS OF SECURITIES

Set forth below is the number of record holders as of September 30, 2018, of each class of securities of the Registrant:

Title of Class		Number of Record Holders
Common Shares of Beneficial interest, par value $0.01 per share		8,843
Auction Preferred Shares - Series A, par value $0.01 per share		16
Auction Preferred Shares - Series B, par value $0.01 per share		16

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ITEM 30.

INDEMNIFICATION

The Registrant's By-Laws, filed in the Registrant’s Registration Statement, and the Form of Distribution Agreement filed herewith contain provisions limiting the liability, and providing for indemnification, of the Trustees and officers under certain circumstances.

Registrant's Trustees and officers are insured under a standard investment company errors and omissions insurance policy covering loss incurred by reason of negligent errors and omissions committed in their official capacities as such. Insofar as indemnification for liabilities arising under the Securities Act of 1933, as amended (the “Securities Act”), may be permitted to directors, officers and controlling persons of the Registrant pursuant to the provisions described in this Item 30, or otherwise, the Registrant has been advised that in the opinion of the Securities and Exchange Commission such indemnification is against public policy as expressed in the Securities Act and is therefore unenforceable. In the event that a claim for indemnification against such liabilities (other than the payment by the Registrant of expenses incurred or paid by a director, officer or controlling person of the Registrant in the successful defense of any action, suit or proceeding) is asserted by such director, officer or controlling person in connection with the securities being registered, the Registrant will, unless in the opinion of its counsel the matter has been settled by controlling precedent, submit to a court of appropriate jurisdiction the question whether such indemnification by it is against public policy as expressed in the Securities Act and will be governed by the final adjudication of such issue.

ITEM 31.

BUSINESS AND OTHER CONNECTIONS OF INVESTMENT ADVISER

Reference is made to: (i) the information set forth under the caption “Investment advisory and other services” in the Statement of Additional Information; (ii) the Eaton Vance Corp. 10-K filed under the Securities Exchange Act of 1934 (File No. 001-8100); and (iii) the Form ADV of Eaton Vance Management (File No. 801-15930) filed with the Commission, all of which are incorporated herein by reference.

ITEM 32.

LOCATION OF ACCOUNTS AND RECORDS

All applicable accounts, books and documents required to be maintained by the Registrant by Section 31(a) of the Investment Company Act of 1940 and the Rules promulgated thereunder are in the possession and custody of the Registrant's custodian, State Street Bank and Trust Company, State Street Financial Center, One Lincoln Street, Boston, MA 02111, and its transfer agent, American Stock Transfer & Trust Company, LLC, 6201 15^th Avenue, Brooklyn, NY 11219, with the exception of certain corporate documents and portfolio trading documents which are in the possession and custody of Eaton Vance Management, Two International Place, Boston, MA 02110. Registrant is informed that all applicable accounts, books and documents required to be maintained by registered investment advisers are in the custody and possession of Eaton Vance Management.

ITEM 33.

MANAGEMENT SERVICES

Not applicable.

ITEM 34.

UNDERTAKINGS

1. The Registrant undertakes to suspend offering of Common Shares until the prospectus is amended if (1) subsequent to the effective date of this Registration Statement, the net asset value declines more than 10 percent from its net asset value as of the effective date of this Registration Statement or (2) the net asset value increases to an amount greater than its net proceeds as stated in the prospectus.

2. Not applicable.

3. Not applicable.

4. The Registrant undertakes to

(a) file, during any period in which offers or sales are being made, a post-effective amendment to the registration statement:

(1) to include any prospectus required by Section 10(a)(3) of the Securities Act;

C-5

(2) to reflect in the prospectus any facts or events after the effective date of the registration statement (or the most recent post-effective amendment thereof) which, individually or in the aggregate, represent a fundamental change in the information set forth in the registration statement;

(3) to include any material information with respect to the plan of distribution not previously disclosed in the registration statement or any material change to such information in the registration statement.

(b) that, for the purpose of determining any liability under the Securities Act, each such post-effective amendment shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of those securities at that time shall be deemed to be the initial bona fide offering thereof;

(c) to remove from registration by means of a post-effective amendment any of the securities being registered which remain unsold at the termination of the offering;

(d) that, for the purpose of determining liability under the Securities Act to any purchaser, if the Registrant is subject to Rule 430C: Each prospectus filed pursuant to Rule 497(b), (c), (d) or (e) under the Securities Act as part of a registration statement relating to an offering, other than prospectus filed in reliance on Rule 430A under the Securities Act, shall be deemed to be part of and included in the registration statement as of the date it is first used after effectiveness. Provided, however, that no statement made in a registration statement or prospectus that is part of the registration statement or made in a document incorporated or deemed incorporated by reference into the registration statement or prospectus that is part of the registration statement will, as to a purchaser with a time of contract of sale prior to such first use, supersede or modify any statement that was made in the registration statement or prospectus that was part of the registration statement or made in any such document immediately prior to such date of first use;

(e) that for the purpose of determining liability of the Registrant under the Securities Act to any purchaser in the initial distribution of securities: The undersigned Registrant undertakes that in a primary offering of securities of the undersigned Registrant pursuant to this registration statement, regardless of the underwriting method used to sell the securities to the purchaser, if the securities are offered or sold to such purchaser by means of any of the following communications, the undersigned Registrant will be a seller to the purchaser and will be considered to offer or sell such securities to the purchaser:

(1) any preliminary prospectus or prospectus of the undersigned Registrant relating to the offering required to be filed pursuant to Rule 497 under the Securities Act;

(2) the portion of any advertisement pursuant to Rule 482 under the Securities Act relating to the offering containing material information about the undersigned Registrant or its securities provided by or on behalf of the undersigned Registrant; and

(3) any other communication that is an offer in the offering made by the undersigned Registrant to the purchaser.

5. The Registrant undertakes that:

(a) for the purpose of determining any liability under the Securities Act, the information omitted from the form of prospectus filed as part of this Registration Statement in reliance upon Rule 430A and contained in the form of prospectus filed by the Registrant pursuant to 497(h) under the Securities Act shall be deemed to be part of the Registration Statement as of the time it was declared effective; and

(b) for the purpose of determining any liability under the Securities Act, each post- effective amendment that contains a form of prospectus shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

6. The Registrant undertakes to send by first class mail or other means designed to ensure equally prompt delivery, within two business days of receipt of an oral or written request, its Statement of Additional Information.

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NOTICE

A copy of the Agreement and Declaration of Trust of Eaton Vance Senior Income Trust is on file with the Secretary of State of The Commonwealth of Massachusetts and notice is hereby given that this instrument is executed on behalf of the Registrant by an officer of the Registrant as an officer and not individually and that the obligations of or arising out of this instrument are not binding upon any of the Trustees, officers or shareholders individually, but are binding only upon the assets and property of the Registrant.

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SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, as amended and the Investment Company Act of 1940, as amended the Registrant has duly caused this Amendment to the Registration Statement to be signed on its behalf by the undersigned, thereunto duly authorized in the City of Boston and the Commonwealth of Massachusetts, on the 24^th day of October 2018.

	EATON VANCE SENIOR INCOME TRUST

	By:	/s/ Payson F. Swaffield
		Payson F. Swaffield, President

Pursuant to the requirements of the Securities Act of 1933, as amended this Registration Statement has been signed by the following persons in the capacities and on the dates indicated.

Signature		Title

/s/ Payson F. Swaffield		President (Chief Executive Officer)
Payson F. Swaffield

/s/ James F. Kirchner		Treasurer (Principal Financial and Accounting Officer)
James F. Kirchner

Signature		Title	Signature	Title

Thomas E. Faust Jr.*		Trustee	Helen Frame Peters*	Trustee
Thomas E. Faust Jr.			Helen Frame Peters

Mark R. Fetting*		Trustee	Keith Quinton*	Trustee
Mark R. Fetting			Keith Quinton

Cynthia E. Frost*		Trustee	Marcus L. Smith*	Trustee
Cynthia E. Frost			Marcus L. Smith

George J. Gorman*		Trustee	Susan J. Sutherland*	Trustee
George J. Gorman			Susan J. Sutherland

Valerie A. Mosley*		Trustee	Harriett Tee Taggart*	Trustee
Valerie A. Mosley			Harriett Tee Taggart

William H. Park*		Trustee	Scott E. Wennerholm*	Trustee
William H. Park			Scott E. Wennerholm

*By:	/s/ Maureen A. Gemma
	Maureen A. Gemma (As attorney-in-fact)