Subject to Completion

Dated October 4, 2018

PRELIMINARY TERMS SUPPLEMENT

Filed Pursuant to Rule 424(b)(2)

Registration Statement No. 333-204908

Preliminary Terms Supplement

UBS AG Trigger Phoenix Autocallable Optimization Securities

UBS AG $ Securities Linked to the common stock of Amazon.com, Inc. due on or about October 8, 2020

Indicative Terms

Issuer

UBS AG, London Branch

Principal Amount

$10.00 per security. The Securities are offered at a minimum investment of 100 Securities at $10.00 per Security (representing a $1,000 investment) and integral multiples of $10.00 in excess thereof.

Term

Approximately 24 months, unless called earlier.

Underlying Equity

The common stock of Amazon.com, Inc.

Contingent Coupon

If the closing price of the underlying equity is equal to or greater than the coupon barrier on any observation date, UBS will pay you the contingent coupon applicable to such observation date.

If the closing price of the underlying equity is less than the coupon barrier on any observation date, the contingent coupon applicable to such observation date will not be payable and UBS will not make any payment to you on the relevant coupon payment date.

The contingent coupon will be a fixed amount based upon equal quarterly installments at the per annum contingent coupon rate. Contingent coupons are not guaranteed and UBS will not pay you the contingent coupon for any observation date on which the closing price of the underlying equity is less than the coupon barrier. The table below sets forth each observation date and a hypothetical contingent coupon for the Securities. The table below assumes a contingent coupon rate of 7.22% per annum. The actual contingent coupon rate will be set at the time the trade is placed on the trade date. Amounts in the table below may have been rounded for ease of analysis.

Observation Date*

Contingent Coupon (per security)

04-Jan-2019

$0.1805

04-Apr-2019

$0.1805

05-Jul-2019

$0.1805

04-Oct-2019

$0.1805

06-Jan-2020

$0.1805

06-Apr-2020

$0.1805

06-Jul-2020

$0.1805

05-Oct-2020

$0.1805

*Observation dates are subject to the market disruption event provisions set forth in the Trigger Phoenix Autocallable Optimization Securities product supplement (“TPAOS product supplement”).

Contingent Coupon Rate

7.22% to 7.62% per annum (or approximately 1.805% to 1.905% per outstanding quarter). The actual contingent coupon rate will be set at the time the trade is placed on the trade date.

Automatic Call Feature

The Securities will be called automatically if the closing price of the underlying equity on any observation date is equal to or greater than the initial price. If the Securities are called on any observation date, UBS will pay you on the corresponding coupon payment date a cash payment per Security equal to your principal amount plus the contingent coupon otherwise due on such date pursuant to the contingent coupon feature. No further amounts will be owed to you under the Securities.

Payment at Maturity

(per Security)

If the Securities are not called and the final price is equal to or greater than the trigger price and coupon barrier, UBS will pay you a cash payment per Security on the maturity date equal to your principal plus the contingent coupon otherwise due on the maturity date.

If the Securities are not called and the final price is less than the trigger price, UBS will pay you a cash payment on the maturity date of significantly less than the principal amount, if anything, resulting in a loss of principal that is proportionate to the decline of the underlying equity, for an amount equal to $10 + ($10 x underlying return).

Underlying Return

Final Price – Initial Price

Initial Price

Closing Price

On any trading day, the last reported sale price (or, in the case of NASDAQ, the official closing price) of the underlying equity during the principal trading session on the principal national securities exchange on which it is listed for trading, as determined by the calculation agent.

Initial Price

The closing price of the underlying equity on the trade date. The initial price is subject to adjustments in the case of certain corporate events, as described in the TPAOS product supplement.

Trigger Price/Coupon Barrier

Both 61.00% of the initial price of the underlying equity. The trigger price and coupon barrier are subject to adjustments in the case of certain corporate events, as described in the TPAOS product supplement.

Final Price

The closing price of the underlying equity on the final valuation date. The final price is subject to adjustment in the case of certain corporate events, as described in the TPAOS product supplement.

Trade Date

October 4, 2018

Settlement Date

October 9, 2018

Final Valuation Date

October 5, 2020. The final valuation date may be subject to postponement in the event of a market disruption event, as described in the TPAOS product supplement.

Maturity Date

October 8, 2020. The maturity date may be subject to postponement in the event of a market disruption event, as described in the TPAOS product supplement.

Coupon Payment Dates

Three business days following each observation date, except the coupon payment date for the final valuation date will be the maturity date.

CUSIP

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ISIN

[]

Valoren

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Tax Treatment

There is no tax authority that specifically addresses the tax treatment of the Securities. UBS and you agree, in the absence of a statutory, regulatory, administrative or judicial ruling to the contrary, to characterize the Securities as a pre-paid derivative contract with respect to the underlying equity and to treat any contingent coupon received by you (including on maturity or upon automatic call) as ordinary income in accordance with your regular method of accounting. Under this characterization you should generally recognize capital gain or loss upon the sale, automatic call, redemption or maturity of your Securities in an amount equal to the amount you receive at such time (other than with respect to any contingent coupon) and the amount that you paid for your Securities.

Section 871(m). A 30% withholding tax (which may be reduced by an applicable income tax treaty) is imposed on certain “dividend equivalent payments” made to a non-U.S. holder with respect to a “specified equity-linked instrument” that references one or more dividend-paying U.S. equity securities. The withholding tax can apply even if the instrument does not provide for payments that reference dividends. Treasury regulations provide that the withholding tax applies to all dividend equivalent payments made on specified equity-linked instruments issued after 2016. However, on December 2, 2016, the IRS issued Notice 2016-76, which states that the Treasury Department and the IRS intend to amend the applicability dates of the Treasury regulations to provide that the withholding tax will apply to all dividend equivalent payments made on specified equity-linked instruments that have a delta of one (“delta one specified equity-linked instruments”) issued after 2016 and to all dividend equivalent payments made on all specified equity-linked instruments issued after 2017. We have determined that the Securities are not delta one specified equity-linked instruments and, therefore, will not be subject to withholding on dividend equivalent payments. However, it is possible that the Securities could be deemed to be reissued for tax purposes upon the occurrence of certain events affecting the Securities or the underlying equity, and following such occurrence the Securities could be treated as delta one specified equity-linked instruments that are subject to withholding on dividend equivalent payments.  It is also possible that withholding tax or other Section 871(m) tax could apply to the Securities under these rules if a non-U.S. holder enters, or has entered, into certain other transactions in respect of the underlying equity or the Securities. Because of the uncertainty regarding the application of the 30% withholding tax on dividend equivalent payments to the Securities, non-U.S. holders are urged to consult their tax advisor regarding the potential application of Section 871(m) (including in the context of their other transactions in respect of the underlying equity or the Securities, if any) and the 30% withholding tax to an investment in the Securities.

For greater detail and possible alternative tax treatments please see the section entitled “What Are the Tax Consequences of the Securities?” on page 12 of the prospectus supplement and the section entitled “Supplemental U.S. Tax Considerations” beginning on page PS-47 of the TPAOS product supplement.

Offering of Securities

Issue Price to Public

Underwriting Discount

Proceeds to UBS AG

Total

Per Security

Total

Per Security

Total

Per Security

Amazon.com, Inc.

$

100%

$

1.50%

$

98.50%

UBS Financial Services Inc.

UBS Investment Bank

Additional Information About UBS and the Securities

•

Prospectus supplement dated May 2, 2016:

http://www.sec.gov/Archives/edgar/data/1114446/000119312516571174/d164032d424b2.htm

•

TPAOS product supplement dated May 2, 2016:

http://www.sec.gov/Archives/edgar/data/1114446/000119312516570716/d186374d424b2.htm

•

Prospectus dated April 29, 2016:

http://www.sec.gov/Archives/edgar/data/1114446/000119312516569341/d161008d424b3.htm

Key Risks

An investment in the Securities involves significant risks. Some of the risks that apply to the Securities are summarized here and are comparable to the corresponding risks discussed in the "Key Risks" section of the prospectus supplement, but we urge you to read the more detailed explanation of risks relating to the Securities generally in ‘‘Risk Factors’’ section of the TPAOS product supplement. We also urge you to consult your investment, legal, tax, accounting and other advisors before you invest in the Securities.

•

Risk of loss at maturity - The Securities differ from ordinary debt securities in that UBS will not necessarily pay the full principal amount of the Securities at maturity. If the Securities are not called, UBS will repay you the principal amount of your Securities in cash only if the final price of the underlying equity is greater than or equal to the trigger price and will only make such payment at maturity. If the Securities are not called and the final price is less than the trigger price, you will be fully exposed to the negative underlying return and lose some or all of your initial investment in an amount proportionate to the decline in the price of the underlying equity.

•

The contingent repayment of your principal applies only at maturity - You should be willing to hold your Securities to maturity. If you are able to sell your Securities prior to maturity in the secondary market, you may have to sell them at a loss relative to your initial investment even if the underlying equity price is above the trigger price.

•

You may not receive any contingent coupons - UBS will not necessarily pay periodic contingent coupons on the Securities. If the closing price of the underlying equity on an observation date is less than the coupon barrier, UBS will not pay you the contingent coupon applicable to such observation date. If the closing price of the underlying equity is less than the coupon barrier on each of the observation dates, UBS will not pay you any contingent coupons during the term of, and you will not receive a positive return on, your Securities. Generally, this non-payment of the contingent coupon coincides with a period of greater risk of principal loss on your Securities.

•

Your potential return on the Securities is limited and you will not participate in any appreciation of the underlying equity - The return potential of the Securities is limited to the contingent coupon rate, regardless of the appreciation of the underlying equity. In addition, the total return on the Securities will vary based on the number of observation dates on which the requirements of the contingent coupon have been met prior to maturity or an automatic call. Further, if the Securities are called due to the automatic call feature, you will not receive any contingent coupons or any other payment in respect of any observation dates after the applicable call settlement date. Since the Securities could be called as early as the first observation date, the total return on the Securities could be minimal. If the Securities are not called, you will not participate in any appreciation in the price of the underlying equity even though you will be subject to the underlying equity’s risk of decline. As a result, the return on an investment in the Securities could be less than the return on a direct investment in the underlying equity.

•

Higher contingent coupon rates are generally associated with a greater risk of loss - Greater expected volatility with respect to the underlying equity reflects a higher expectation as of the trade date that the price of such underlying equity could close below its trigger price on the final valuation date of the Securities. This greater expected risk will generally be reflected in a higher contingent coupon rate for that Security. However, an underlying equity’s volatility can change significantly over the term of the Securities and the price of the underlying equity for your Securities could fall sharply, which could result in a significant loss of principal.

•

Reinvestment risk - The Securities will be called automatically if the closing price of the underlying equity is equal to or greater than the initial price on any observation date. In the event that the Securities are called prior to maturity, there is no guarantee that you will be able to reinvest the proceeds from an investment in the Securities at a comparable rate of return for a similar level of risk. To the extent you are able to reinvest such proceeds in an investment comparable to the Securities, you will incur transaction costs and the original issue price for such an investment is likely to include certain built-in costs such as dealer discounts and hedging costs.

•

Credit risk of UBS - The Securities are unsubordinated, unsecured debt obligations of the issuer, UBS, and are not, either directly or indirectly, an obligation of any third party. Any payment to be made on the Securities, including any repayment of principal, depends on the ability of UBS to satisfy its obligations as they come due. As a result, the actual and perceived creditworthiness of UBS may affect the market value of the Securities and, in the event UBS were to default on its obligations, you may not receive any amounts owed to you under the terms of the Securities and you could lose your entire investment.

•

Market risk - The price of the underlying equity can rise or fall sharply due to factors specific to that underlying equity and (i) in the case of common stock or American depositary shares, its issuer (the "underlying equity issuer") or (ii) in the case of an exchange traded fund, the securities, futures contracts or physical commodities constituting the assets of that underlying equity. These factors include price volatility, earnings, financial conditions, corporate, industry and regulatory developments, management changes and decisions and other events, as well as general market factors, such as general market volatility and levels, interest rates and economic and political conditions. You, as an investor in the Securities, should make your own investigation into the underlying equity issuer and the underlying equity for your Securities. We urge you to review financial and other information filed periodically by the underlying equity issuer with the SEC.

•

Fair value considerations.

•

The issue price you pay for the Securities will exceed their estimated initial value - The issue price you pay for the Securities will exceed their estimated initial value as of the trade date due to the inclusion in the issue price of the underwriting discount, hedging costs, issuance costs and projected profits. As of the close of the relevant markets on the trade date, we will determine the estimated initial value of the Securities by reference to our internal pricing models and it will be set forth in the final terms supplement. The pricing models used to determine the estimated initial value of the Securities incorporate certain variables, including the price, volatility and expected dividends on the underlying equity, prevailing interest rates, the term of the Securities and our internal funding rate. Our internal funding rate is typically lower than the rate we would pay to issue conventional fixed or floating rate debt securities of a similar term. The underwriting discount, hedging costs, issuance costs, projected profits and the difference in rates will reduce the economic value of the Securities to you. Due to these factors, the estimated initial value of the Securities as of the trade date will be less than the issue price you pay for the Securities.

•

The estimated initial value is a theoretical price; the actual price that you may be able to sell your Securities in any secondary market (if any) at any time after the trade date may differ from the estimated initial value - The value of your Securities at any time will vary based on many factors, including the factors described above and in “- Market risk” above and is impossible to predict. Furthermore, the pricing models that we use are proprietary and rely in part on certain assumptions about future events, which may prove to be incorrect. As a result, after the trade date, if you attempt to sell the Securities in the secondary market, the actual value you would receive may differ, perhaps materially, from the estimated initial value of the Securities determined by reference to our internal pricing models. The estimated initial value of the Securities does not represent a minimum or maximum price at which we or any of our affiliates would be willing to purchase your Securities in any secondary market at any time.

•

Our actual profits may be greater or less than the differential between the estimated initial value and the issue price of the Securities as of the trade date - We may determine the economic terms of the Securities, as well as hedge our obligations, at least in part, prior to pricing the Securities on the trade date. In addition, there may be ongoing costs to us to maintain and/or adjust any hedges and such hedges are often imperfect. Therefore, our actual profits (or potentially, losses) in issuing the Securities cannot be determined as of the trade date and any such differential between the estimated initial value and the issue price of the Securities as of the trade date does not reflect our actual profits. Ultimately, our actual profits will be known only at the maturity of the Securities.

•

Limited or no secondary market and secondary market price considerations.

•

There may be little or no secondary market for the Securities - The Securities will not be listed or displayed on any securities exchange or any electronic communications network. There can be no assurance that a secondary market for the Securities will develop. UBS Securities LLC and its affiliates may make a market in each offering of the Securities, although they are not required to do so and may stop making a market at any time. If you are able to sell your Securities prior to maturity, you may have to sell them at a substantial loss. The estimated initial value of the Securities does not represent a minimum or maximum price at which we or any of our affiliates would be willing to purchase your Securities in any secondary market at any time.

•

The price at which UBS Securities LLC and its affiliates may offer to buy the Securities in the secondary market (if any) may be greater than UBS’ valuation of the Securities at that time, greater than any other secondary market prices provided by unaffiliated dealers (if any) and, depending on your broker, greater than the valuation provided on your customer account statements - For a limited period of time following the issuance of the Securities, UBS Securities LLC or its affiliates may offer to buy or sell such Securities at a price that exceeds (i) our valuation of the Securities at that time based on our internal pricing models, (ii) any secondary market prices provided by unaffiliated dealers (if any) and (iii) depending on your broker, the valuation provided on customer account statements. The price that UBS Securities LLC may initially offer to buy such Securities following issuance will exceed the valuations indicated by our internal pricing models due to the inclusion for a limited period of time of the aggregate value of the underwriting discount, hedging costs, issuance costs and theoretical projected trading profit. The portion of such amounts included in our price will decline to zero on a straight line basis over a period ending no later than the date specified under “Supplemental Plan of Distribution (Conflicts of Interest); Secondary Markets (if any).” Thereafter, if UBS Securities LLC or an affiliate makes secondary markets for the Securities, it will do so at prices that reflect our estimated value determined by reference to our internal pricing models at that time. The temporary positive differential relative to our internal pricing models arises from requests from and arrangements made by UBS Securities LLC with the selling agents of structured debt securities such as the Securities. As described above, UBS Securities LLC and its affiliates are not required to make a market for the Securities and may stop making a market at any time. The price at which UBS Securities LLC or an affiliate may make secondary markets at any time (if at all) will also reflect its then current bid-ask spread for similar sized trades of structured debt securities. UBS Financial Services Inc. and UBS Securities LLC reflect this temporary positive differential on their customer statements. Investors should inquire as to the valuation provided on customer account statements provided by unaffiliated dealers.

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Price of Securities prior to maturity - The market price of the Securities will be influenced by many unpredictable and interrelated factors, including the price of the underlying equity; the volatility of the underlying equity; the dividend rate paid on the underlying equity; the time remaining to the maturity of the Securities; interest rates in the markets; geopolitical conditions and economic, financial, political, force majeure and regulatory or judicial events; the creditworthiness of UBS and the then current bid-ask spread for the Securities.

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Impact of fees and the use of internal funding rates rather than secondary market credit spreads on secondary market prices - All other things being equal, the use of the internal funding rates described above under “- Fair value considerations” as well as the inclusion in the issue price of the underwriting discount, hedging costs, issuance costs and any projected profits are, subject to the temporary mitigating effect of UBS Securities LLC’s and its affiliates’ market making premium, expected to reduce the price at which you may be able to sell the Securities in any secondary market.

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Owning the Securities is not the same as owning the underlying equity - The return on your Securities may not reflect the return you would realize if you actually owned the underlying equity. For instance, you will not receive or be entitled to receive any dividend payments or other distributions on the underlying equity over the term of your Securities. Furthermore, the underlying equity may appreciate substantially during the term of your Securities and you will not participate in such appreciation.

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No assurance that the investment view implicit in the Securities will be successful - It is impossible to predict whether and the extent to which the price of the underlying equity will rise or fall. The price of the underlying equity will be influenced by complex and interrelated political, economic, financial and other factors that affect the issuer of the underlying equity. You should be willing to accept the risks of owning equities in general and the underlying equity in particular, and the risk of losing some or all of your initial investment.

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There is no affiliation between the underlying equity issuer, or for Securities linked to exchange traded funds, the issuers of the constituent stocks comprising the underlying equity (the "underlying equity constituent stock issuers"), and UBS, and UBS is not responsible for any disclosure by such issuer(s) - We and our affiliates may currently, or from time to time in the future engage in business with the underlying equity issuer or, if applicable, any underlying equity constituent stock issuers. However, we are not affiliated with the underlying equity issuer or any underlying equity constituent stock issuers and are not responsible for such issuer’s public disclosure of information, whether contained in SEC filings or otherwise. You, as an investor in the Securities, should make your own investigation into the underlying equity issuer or, if applicable, each underlying equity constituent stock issuer. Neither the underlying equity issuer nor any underlying equity constituent stock issuer is involved in the Securities offered hereby in any way and has no obligation of any sort with respect to your Securities. Such issuer(s) have no obligation to take your interests into consideration for any reason, including when taking any corporate actions that might affect the value of your Securities.

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The calculation agent can make adjustments that affect the payment to you at maturity- For certain corporate events affecting the underlying equity, the calculation agent may make adjustments to the initial price, the coupon barrier, the trigger price and/or the final price of the underlying equity. However, the calculation agent will not make an adjustment in response to all events that could affect the underlying equity. If an event occurs that does not require the calculation agent to make an adjustment, the value of the Securities may be materially and adversely affected. In addition, all determinations and calculations concerning any such adjustments will be made by the calculation agent. You should be aware that the calculation agent may make any such adjustment, determination or calculation in a manner that differs from that discussed in the TPAOS product supplement as necessary to achieve an equitable result. In the case of common stock or American depositary shares, following certain corporate events relating to the issuer of the underlying equity where the issuer is not the surviving entity, the amount of cash you receive at maturity may be based on the common stock or American depositary share of a successor to the underlying equity issuer in combination with any cash or any other assets distributed to holders of the underlying equity in such corporate event. Additionally, if the issuer of the underlying equity becomes subject to (i) a reorganization event whereby the underlying equity is exchanged solely for cash, (ii) a merger or consolidation with UBS or any of its affiliates or (iii) an underlying equity is delisted or otherwise suspended from trading, the amount you receive at maturity may be based on the common stock or American depositary shares issued by another company. In the case of an exchange traded fund, following a suspension from trading or if an exchange traded fund is discontinued, the amount you receive at maturity may be based on a share of another exchange traded fund. The occurrence of these corporate events and the consequent adjustments may materially and adversely affect the value of the Securities. For more information, see the section “General Terms of the Securities — Antidilution Adjustments” beginning on page PS-34 of the TPAOS product supplement. Regardless of any of the events discussed above, any payment on the Securities is subject to the creditworthiness of UBS.

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Potential UBS impact on the market price of the underlying equity - Trading or transactions by UBS or its affiliates in the underlying equity and/or over-the-counter options, futures or other instruments with returns linked to the performance of the underlying equity may adversely affect the market price of the underlying equity and, therefore, the market value of your Securities.

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Potential conflict of interest - UBS and its affiliates may engage in business with the issuer of the underlying equity, which may present a conflict between the obligations of UBS and you, as a holder of the Securities. There are also potential conflicts of interest between you and the calculation agent, which will be an affiliate of UBS. The calculation agent will determine whether the final price is below the trigger price and accordingly the payment at maturity on your Securities. The calculation agent may also postpone the determination of the final price and the maturity date if a market disruption event occurs and is continuing on the final valuation date and may make adjustments to the initial price, the trigger price, the coupon barrier, the final price and/or the underlying equity itself for certain corporate events affecting the underlying equity. For more information, see the section “General Terms of the Securities — Antidilution Adjustments” beginning on page PS-34 of the TPAOS product supplement. As UBS determines the economic terms of the Securities, including the contingent coupon rate, trigger price and coupon barrier, and such terms include hedging costs, issuance costs and projected profits, the Securities represent a package of economic terms. There are other potential conflicts of interest insofar as an investor could potentially get better economic terms if that investor entered into exchange-traded and/or OTC derivatives or other instruments with third parties, assuming that such instruments were available and the investor had the ability to assemble and enter into such instruments.

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Potentially inconsistent research, opinions or recommendations by UBS - UBS and its affiliates publish research from time to time on financial markets and other matters that may influence the value of the Securities, or express opinions or provide recommendations that are inconsistent with purchasing or holding the Securities. Any research, opinions or recommendations expressed by UBS or its affiliates may not be consistent with each other and may be modified from time to time without notice. Investors should make their own independent investigation of the merits of investing in the Securities and the underlying equity to which the Securities are linked.

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The Securities are not bank deposits: An investment in the Securities carries risks which are very different from the risk profile of a bank deposit placed with UBS or its affiliates. The Securities have different yield and/or return, liquidity and risk profiles and would not benefit from any protection provided to deposits.

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Under certain circumstances, the Swiss Financial Market Supervisory Authority (FINMA) has the power to take actions that may adversely affect the Securities - Pursuant to article 25 et seq. of the Swiss Banking Act, FINMA has broad statutory powers to take measures and actions in relation to UBS if it (i) is overindebted, (ii) has serious liquidity problems or (iii) fails to fulfill the applicable capital adequacy provisions after expiration of a deadline set by FINMA. If one of these prerequisites is met, the Swiss Banking Act grants significant discretion to FINMA to open restructuring proceedings or liquidation (bankruptcy) proceedings in respect of, and/or impose protective measures in relation to, UBS. In particular, a broad variety of protective measures may be imposed by FINMA, including a bank moratorium or a maturity postponement, which measures may be ordered by FINMA either on a stand-alone basis or in connection with restructuring or liquidation proceedings. In a restructuring proceeding, the resolution plan may, among other things, (a) provide for the transfer of UBS’s assets or a portion thereof, together with debts and other liabilities, and contracts of UBS, to another entity, (b) provide for the conversion of UBS’s debt and/or other obligations, including its obligations under the Securities, into equity, and/or (c) potentially provide for haircuts on obligations of UBS, including its obligations under the Securities. Although no precedent exists, if one or more measures under the revised regime were imposed, such measures may have a material adverse effect on the terms and market value of the Securities and/or the ability of UBS to make payments thereunder.

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Dealer incentives - UBS and its affiliates act in various capacities with respect to the Securities. We and our affiliates may act as a principal, agent or dealer in connection with the sale of the Securities. Such affiliates, including the sales representatives, will derive compensation from the distribution of the Securities and such compensation may serve as an incentive to sell these Securities instead of other investments. We will pay total underwriting compensation of 1.50% per Security to any of our affiliates acting as agents or dealers in connection with the distribution of the Securities. Given that UBS Securities LLC and its affiliates temporarily maintain a market making premium, it may have the effect of discouraging UBS Securities LLC and its affiliates from recommending sale of your Securities in the secondary market.

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Uncertain tax treatment - Significant aspects of the tax treatment of the Securities are uncertain. You should read carefully the sections entitled "What are the Tax Consequences of the Securities" in the prospectus supplement and “Supplemental U.S. Tax Considerations” beginning on page PS-47 of the TPAOS product supplement and consult your tax advisor about your tax situation.

Information about the Underlying Equity

All disclosures regarding the underlying equity are derived from publicly available information. UBS has not conducted any independent review or due diligence of any publicly available information with respect to the underlying equity. You should make your own investigation into the underlying equity.

The underlying equity will be registered under the Securities Exchange Act of 1934, as amended (the ‘‘Exchange Act’’). Companies with securities registered under the Exchange Act are required to file financial and other information specified by the SEC periodically. Information filed by the issuer of the underlying equity with the SEC can be reviewed electronically through a website maintained by the SEC. The address of the SEC’s website is http://www.sec.gov. Information filed with the SEC by the issuer of the underlying equity under the Exchange Act can be located by reference to its SEC file number provided below. In addition, information filed with the SEC can be inspected and copied at the Public Reference Section of the SEC, 100 F Street, N.E., Room 1580, Washington, D.C. 20549. Copies of this material can also be obtained from the Public Reference Section, at prescribed rates.

Amazon.com, Inc.

Quarter Begin

Quarter End

Quarterly High

Quarterly Low

Quarterly Close

01/02/2014

03/31/2014

$407.05

$336.52

$336.52

04/01/2014

06/30/2014

$342.99

$288.32

$324.78

07/01/2014

09/30/2014

$360.84

$307.06

$322.44

10/01/2014

12/31/2014

$338.64

$287.06

$310.35

01/02/2015

03/31/2015

$387.83

$286.95

$372.10

04/01/2015

06/30/2015

$445.99

$370.26

$434.09

07/01/2015

09/30/2015

$548.39

$429.70

$511.89

10/01/2015

12/31/2015

$693.97

$520.72

$675.89

01/04/2016

03/31/2016

$636.99

$482.07

$593.64

04/01/2016

06/30/2016

$728.24

$586.14

$715.62

07/01/2016

09/30/2016

$837.31

$725.68

$837.31

10/03/2016

12/30/2016

$844.36

$719.07

$749.87

01/03/2017

03/31/2017

$886.54

$753.67

$886.54

04/03/2017

06/30/2017

$1,011.34

$884.67

$968.00

07/03/2017

09/29/2017

$1,052.80

$938.60

$961.35

10/02/2017

12/29/2017

$1,195.83

$957.10

$1,169.47

01/02/2018

03/29/2018

$1,598.39

$1,189.01

$1,447.34

04/02/2018

06/29/2018

$1,750.08

$1,371.99

$1,699.80

07/02/2018

09/28/2018

$2,039.51

$1,693.96

$2,003.00

10/01/2018*

10/03/2018*

$2,004.36

$1,952.76

$1,952.76

Supplemental Plan of Distribution (Conflicts of Interest); Secondary Markets (if any)

We will agree to sell to UBS Securities LLC and UBS Securities LLC will agree to purchase, all of the Securities at the issue price to the public less the underwriting discount indicated on the cover of the final terms supplement, the document that will be filed pursuant to Rule 424(b) containing the final pricing terms of the Securities. UBS Securities LLC will agree to resell all of the Securities to UBS Financial Services Inc. at a discount from the issue price to the public equal to the underwriting discount indicated on the cover of the final terms supplement.

Conflicts of Interest - Each of UBS Securities LLC and UBS Financial Services Inc. is an affiliate of UBS and, as such, has a "conflict of interest" in this offering within the meaning of FINRA Rule 5121. In addition, UBS will receive the net proceeds (excluding the underwriting discount) from the initial public offering of the Securities and, thus creates an additional conflict of interest within the meaning of FINRA Rule 5121. Consequently, the offering is being conducted in compliance with the provisions of Rule 5121. Neither UBS Securities LLC nor UBS Financial Services Inc. is permitted to sell Securities in the offering to an account over which it exercises discretionary authority without the prior specific written approval of the account holder.

UBS Securities LLC and its affiliates may offer to buy or sell the Securities in the secondary market (if any) at prices greater than UBS’ internal valuation - The value of the Securities at any time will vary based on many factors that cannot be predicted. However, the price (not including UBS Securities LLC’s or any affiliate’s customary bid-ask spreads) at which UBS Securities LLC or any affiliate would offer to buy or sell the Securities immediately after the trade date in the secondary market is expected to exceed the estimated initial value of the Securities as determined by reference to our internal pricing models. The amount of the excess will decline to zero on a straight line basis over a period ending no later than 1 month after the trade date, provided that UBS Securities LLC may shorten the period based on various factors, including the magnitude of purchases and other negotiated provisions with selling agents. Notwithstanding the foregoing, UBS Securities LLC and its affiliates are not required to make a market for the Securities and may stop making a market at any time. For more information about secondary market offers and the estimated initial value of the Securities, see “Key Risks - Fair value considerations” and “Key Risks - Limited or no secondary market and secondary market price considerations” in this preliminary terms supplement.

Prohibition of Sales to EEA Retail Investors — The Securities are not intended to be offered, sold or otherwise made available to and should not be offered, sold or otherwise made available to any retail investor in the European Economic Area (“EEA”). For these purposes, a retail investor means a person who is one (or more) of: (i) a retail client as defined in point (11) of Article 4(1) of Directive 2014/65/EU, as amended (“MiFID II”); (ii) a customer within the meaning of Directive 2002/92/EC, as amended, where that customer would not qualify as a professional client as defined in point (10) of Article 4(1) of MiFID II; or (iii) not a qualified investor as defined in Directive 2003/71/EC, as amended. Consequently no key information document required by Regulation (EU) No 1286/2014 (as amended, the “PRIIPs Regulation”) for offering or selling the Securities or otherwise making them available to retail investors in the EEA has been prepared and therefore offering or selling the Securities or otherwise making them available to any retail investor in the EEA may be unlawful under the PRIIPs Regulation.

You should rely only on the information incorporated by reference or provided in this preliminary terms supplement, the accompanying prospectus supplement, the product supplement or the accompanying prospectus. We have not authorized anyone to provide you with different information. We are not making an offer of these securities in any state where the offer is not permitted. You should not assume that the information in this preliminary terms supplement is accurate as of any date other than the date on the front of the document.

TABLE OF CONTENTS

Preliminary Terms Supplement

Use of Proceeds

12

Description of Debt Securities We May Offer

13

Description of Warrants We May Offer

33

Legal Ownership and Book-Entry Issuance

48

Considerations Relating to Indexed Securities

53

Considerations Relating to Securities Denominated or Payable in or Linked to a Non-U.S. Dollar Currency

56

U.S. Tax Considerations

59

Tax Considerations Under the Laws of Switzerland

70

Benefit Plan Investor Considerations

72

Plan of Distribution

74

Indicative Terms

1

Conflicts of Interest

76

Additional Information About UBS and the Securities

3

Validity of the Securities

77

Key Risks

4

Experts

77

Information About the Underlying Equity

7

$ •

UBS AG Trigger Phoenix Autocallable Optimization Securities due on or about October 8, 2020

Preliminary Terms Supplement dated October 4, 2018

(To Prospectus Supplement dated May 2, 2016,

Product Supplement dated May 2, 2016 and

Prospectus dated April 29, 2016)

UBS Investment Bank

UBS Financial Services Inc.

Amazon.com, Inc.

7

Supplemental Plan of Distribution (Conflicts of Interest); Secondary Markets (if any)

9

Prospectus Supplement

Investment Description

i

Features

i

Security Offerings

i

Additional Information About UBS and the Securities

ii

Investor Suitability

1

Summary Terms

2

Investment Timeline

2

Key Risks

3

Hypothetical Examples of How the Securities Might Perform

8

What are the Tax Consequences of the Securities ?

10

Information About the Underlying Equity

13

Supplemental Plan of Distribution (Conflicts of Interest); Secondary Markets (if any)

13

Annex A – Form of Final Terms Supplement

A-2

Annex B – UBS Equity Investor - Investment Guide

B-2

Product Supplement

Product Supplement Summary

PS-1

Hypothetical Payment Amounts on Your Securities

PS-14

Risk Factors

PS-15

General Terms of the Securities

PS-30

Use of Proceeds and Hedging

PS-47

Supplemental U.S. Tax Considerations

PS-48

Certain ERISA Considerations

PS-56

Supplemental Plan of Distribution (Conflicts of Interest)

PS-57

Prospectus

Introduction

1

Cautionary Note Regarding Forward-Looking Statements

4

Incorporation of Information About UBS AG

5

Where You Can Find More Information

6

Presentation of Financial Information

7

Limitations on Enforcement of U.S. Laws Against UBS AG, Its Management and Others

7

UBS

8

Swiss Regulatory Powers

11