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Overview of the Notes

The Buffer Notes Based Upon the S&P 500 ^® Index due 2011 (the “Notes”), are equity index-linked investments that offer a potential return at maturity based on an enhanced upside participation in any increase in the value of the S&P 500 ^® Index during the term of the Notes, subject to a maximum total return, while also providing full protection against a decline of 10% or less in the value of the S&P 500 ^® Index and limited protection against a decline of more than 10% in the value of the S&P 500 ^® Index. The Notes are not principal protected and do not pay periodic interest. The Notes have a maturity of approximately two years and are issued by Citigroup Funding Inc. Some key characteristics of the Notes include:

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The Notes are a series of unsecured senior debt securities issued by Citigroup Funding. Any payments due on the Notes are fully and unconditionally guaranteed by Citigroup Inc., Citigroup Funding’s parent company. The Notes will rank equally with all other unsecured and unsubordinated debt of Citigroup Funding, and as a result of the guarantee any payments due under the Notes at maturity will rank equally with all other unsecured and unsubordinated debt of Citigroup Inc. The return of the principal amount of your investment in the Notes at maturity is not guaranteed .

The Notes are not deposits or savings accounts, are not insured by the Federal Deposit Insurance Corporation (“FDIC”) or by any other governmental agency or instrumentality, and are not guaranteed by the FDIC under the Temporary Liquidity Guarantee Program.

Types of Investors

The Notes may be an attractive investment for the following types of investors:

Commissions and Fees

Citigroup Global Markets Inc., an affiliate of Citigroup Funding and the underwriter of the sale of the Notes, will receive an underwriting fee of $0.225 for each $10.000 Note sold in this offering. Certain dealers, including Citi International Financial Services, Citigroup Global Markets Singapore Pte. Ltd., and Citigroup Global Markets Asia Limited, broker-dealers affiliated with Citigroup Global Markets, will receive from Citigroup Global Markets $0.200 from this underwriting fee for each Note they sell. Citigroup Global Markets will pay the Financial Advisors employed by Smith Barney, a division of Citigroup Global Markets, a fixed sales commission of $0.200 for each Note they sell. Additionally, it is possible that Citigroup Global Markets and its affiliates may profit from expected hedging activity related to this offering, even if the value of the Notes declines. You should refer to “Key Risk Factors for the Notes” below and “Risk Factors Relating to the Notes” and “Plan of Distribution” in the pricing supplement related to this offering for more information.

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Benefits of the Notes

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The following summarizes certain federal income tax considerations for U.S. investors (“U.S. Holders”) and certain non-U.S. investors described below that are initial holders of the Notes and that hold the Notes as capital assets

For U.S. federal income tax purposes, the Notes generally should be treated as a cash-settled prepaid forward contract, subject to a floor, on the value of the S&P 500 ^® Index on the Valuation Date, pursuant to which forward contract, at maturity the U.S. Holder will receive the cash value of the S&P 500 ^® Index subject to certain adjustments. The amounts invested by a U.S. Holder should be treated as a cash deposit that will be used to satisfy the holder’s obligation under the Note. Thus a U.S. Holder’s tax basis in a Note generally will equal the holder’s cost for that Note. Under the above characterization, at maturity or upon the sale or other taxable disposition of a Note, a U.S. Holder generally will recognize capital gain or loss equal to the difference between the amount the U.S. Holder receives and the holder’s tax basis in the Notes. Such gain or loss generally will be long-term capital gain or loss if the U.S. Holder has held the Notes for more than one year at the time of disposition.

No statutory, judicial or administrative authority directly addresses the characterization of the Notes or instruments similar to the Notes for U.S. federal income tax purposes. As a result, significant aspects of the U.S. federal income tax consequences of an investment in the Notes are not certain. Accordingly, a prospective investor (including a tax-exempt investor) in the Notes should consult his or her tax advisor in determining the tax consequences of an investment in the Notes, including the application of State, Local or other tax laws and the possible effects of changes in Federal or other tax laws.

It is also possible that future regulations or other IRS guidance would require you to accrue income on the Notes on a current basis at ordinary income rates (as opposed to capital gains rates) or to treat the Notes in another manner that significantly differs from the agreed-to treatment discussed above. The IRS and U.S. Treasury Department issued a notice (the “Notice”) that requests public comments on a comprehensive list of tax policy issues raised by prepaid forward contracts, which include financial instruments similar to the Notes. The Notice contemplates that such instruments may become subject to taxation on a current accrual basis under one or more possible approaches, including a mark-to-market methodology; a regime similar to the Contingent

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Payment Regulations; categorization of prepaid forward contracts as debt; and treatment of prepaid forward contracts as “constructive ownership” transactions. The Notice also contemplates that all (or significant portions) of an investor’s returns under prepaid forward contracts could be taxed at ordinary income rates (as opposed to capital gains rates). It is currently impossible to predict what guidance, if any, will be issued as a result of the Notice, and whether any such guidance could have retroactive effect.

In addition, legislation has been introduced for consideration in the United States Congress that, if enacted into law, would require current accrual of interest income on prepaid derivative contracts with a term of more than one year (which would include financial instruments similar to the Notes) acquired after the date of the legislation’s enactment. The legislation also would implement special income accrual rules for publicly traded prepaid derivative contracts. The schedule for consideration of this legislation and the outcome of the legislative process currently is uncertain.

Any capital gain realized by a holder that is not a U.S. person (“Non-U.S. Holder”) upon the sale or other disposition of the Notes should not be subject to U.S. federal income tax if:

In the Notice discussed above, the IRS and U.S. Treasury Department specifically question whether, and to what degree, payments (or deemed accruals) in respect of a prepaid forward contract should be subject to withholding. Accordingly, it is possible that future guidance could be issued as a result of the Notice requiring us to withhold on payments made to non-U.S. Holders under the Notes.

You should refer to the pricing supplement related to this offering for additional information relating to U.S. federal income tax and should consult your own tax advisors to determine tax consequences particular to your situation.

Description of the S&P 500 ^® Index

Unless otherwise stated, we have derived all information regarding the S&P 500 ^® Index provided in this offering summary, including its composition, method of calculation and changes in components, from Standard & Poor’s (“S&P”) publicly available sources and other sources we believe to be reliable. Such information reflects the policies of, and is subject to change by, S&P. S&P is under no obligation to continue to publish, and may discontinue or suspend the publication of, the S&P 500 ^® Index at any time. None of Citigroup Inc., Citigroup Funding, Citigroup Global Markets or the trustee assumes any responsibility for the accuracy or completeness of any information relating to the S&P 500 ^® Index.

The S&P 500 ^® Index is published by S&P and is intended to provide a performance benchmark for the U.S. equity markets. S&P chooses companies for inclusion with an aim of achieving a distribution by broad industry groupings. The calculation of the value is based on the relative aggregate market value of the common stocks of 500 companies at a particular time compared to the aggregate average market value of the common stocks of 500 similar companies during the base period of the years 1941 through 1943. The weighting and composition of the index components are updated periodically so that the S&P 500 ^® Index reflects the performance of the U.S. equity markets.

As of December 31, 2008, the common stocks of 412 of the 500 companies included in the S&P 500 ^® Index were listed on the New York Stock Exchange (the “NYSE”). As of December 31, 2008, the aggregate market value of the 500 companies included in the S&P 500 ^® Index represented approximately 76% of the U.S. equities market. S&P chooses companies for inclusion in the S&P 500 ^® Index with the aim of achieving a distribution by broad industry groupings that approximates the distribution of these groupings in the common stock composition of the NYSE, which S&P uses as an assumed model for the composition of the total market. Relevant criteria employed by S&P include the viability of the particular company, the extent to which that company represents the industry group to which it is assigned, the extent to which the market price of that company’s common stock is generally responsive to changes in the affairs of the respective industry and the market value and trading activity of the common stock of that company.

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As of December 31, 2008, the 500 companies included in the S&P 500 ^® Index were divided into 10 Global Industry Classification Sectors. The Global Industry Classification Sectors included (with the percentage of companies currently included in such sectors indicated in parentheses): Consumer Discretionary (8.4%), Consumer Staples (12.9%), Energy

(13.3%), Financials (13.3%), Health Care (14.8%), Industrials (11.1%), Information Technology (15.3%), Materials (2.9%), Telecommunication Services (3.8%) and Utilities (4.2%). S&P may from time to time, in its sole discretion, add companies to, or delete companies from, the S&P 500 ^® Index to achieve the objectives stated above.

The following table sets forth the closing value of the S&P 500 ^® Index for each month in the period from January 2003 through December 2008. These historical data on the S&P 500 ^® Index are not indicative of the future performance of the S&P 500 ^® Index or what the market value of the Notes may be. Any historical upward

or downward trend in the value of the S&P 500 ^® Index during any period set forth below is not an indication that the S&P 500 ^® Index is more or less likely to increase or decrease at any time during the term of the Notes.

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On January 23, 2009, the closing value of the S&P 500 ^® Index was 831.95.

Additional information on the S&P 500 ^® Index, including its makeup, method of calculation and changes in its components, is included in the pricing supplement related to this offering under “Description of the S&P 500 ^® Index.” All such disclosures in the pricing supplement and the information on the S&P 500 ^® Index

provided in this offering summary are derived from publicly available information. None of Citigroup Funding, Citigroup Inc., or Citigroup Global Markets assumes any responsibility for the accuracy or completeness of such information. You should also be aware that an investment in the Notes does not entitle you to any dividends, voting rights or any other ownership or other interest in respect of the stocks of the companies included in the S&P 500 ^® Index.

S&P and Citigroup Global Markets have entered into a non-exclusive license agreement providing for the license to Citigroup Inc., Citigroup Funding and its affiliates, in exchange for a fee, of the right to use indices owned and published by S&P in connection with certain financial instruments, including the Notes.

The license agreement between S&P and Citigroup Global Markets provides that the following language must be stated in this offering summary.

“The Notes are not sponsored, endorsed, sold or promoted by S&P. S&P makes no representation or warranty, express or implied, to the holders of the Notes or any member of the public regarding the advisability of investing in securities generally or in the Notes particularly. S&P’s only relationship to Citigroup Funding and its affiliates (other than transactions entered into in the ordinary course of business) is the licensing of certain trademarks, trade names and service marks of S&P and of the S&P 500 ^® Index, which is determined,

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composed and calculated by S&P without regard to Citigroup Funding, its affiliates or the Notes. S&P has no obligation to take the needs of Citigroup Funding, its affiliates or the holders of the Notes into consideration in determining, composing or calculating the S&P 500 ^® Index. S&P is not responsible for and has not participated in the determination of the timing of, prices at or quantities of the Notes to be issued or in the determination or calculation of the equation by which the Notes are to be converted into cash. S&P has no obligation or liability in connection with the administration, marketing or trading of the Notes.

S&P DOES NOT GUARANTEE THE ACCURACY AND/OR THE COMPLETENESS OF THE S&P 500 ^® INDEX OR ANY DATA INCLUDED THEREIN AND S&P SHALL HAVE NO LIABILITY FOR ANY ERRORS, OMISSIONS, OR INTERRUPTIONS THEREIN. S&P MAKES NO WARRANTY, EXPRESS OR IMPLIED, AS TO RESULTS TO BE OBTAINED BY CITIGROUP FUNDING, HOLDERS OF THE NOTES, OR ANY OTHER PERSON OR ENTITY FROM THE USE OF THE S&P 500 ^® INDEX OR ANY DATA INCLUDED

THEREIN. S&P MAKES NO EXPRESS OR IMPLIED WARRANTIES, AND EXPRESSLY DISCLAIMS ALL WARRANTIES, OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE OR USE WITH RESPECT TO THE S&P 500 ^® INDEX OR ANY DATA INCLUDED THEREIN. WITHOUT LIMITING ANY OF THE FOREGOING, IN NO EVENT SHALL S&P HAVE ANY LIABILITY FOR ANY LOST PROFITS OR INDIRECT, PUNITIVE, SPECIAL OR CONSEQUENTIAL DAMAGES, EVEN IF NOTIFIED OF THE POSSIBILITY THEREOF. THERE ARE NO THIRD PARTY BENEFICIARIES OF ANY AGREEMENTS OR ARRANGEMENTS BETWEEN S&P AND CITIGROUP FUNDING.”

All disclosures contained in this offering summary regarding the S&P 500 ^® Index, including its makeup, method of calculation and changes in its components, are derived from publicly available information prepared by S&P. None of Citigroup Funding, Citigroup, Citigroup Global Markets Inc. or the trustee assumes any responsibility for the accuracy or completeness of such information.

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Hypothetical Maturity Payments

The examples below show hypothetical maturity payments on the Notes for a range of Ending Values of S&P 500 ^® Index. The following examples are for purposes of illustration only and would provide different results if different assumptions were applied. The value of the actual amount you receive in respect of the Notes at maturity will depend on the actual Note Return Amount, which, in turn, will depend on the actual Starting Value, Ending Value, Upside Participation Rate and maximum total return. All of the hypothetical examples are based on the following assumptions:

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Employee benefit plans subject to ERISA, entities the assets of which are deemed to constitute the assets of such plans, governmental or other plans subject to laws substantially similar to ERISA and retirement accounts (including Keogh, SEP and SIMPLE plans, individual retirement accounts and individual retirement annuities) are permitted to purchase the Notes as long as either (A) (1) no Citigroup Global Markets affiliate or employee is a fiduciary to such plan or retirement account that has or exercises any discretionary authority or control with respect to the assets of such plan or retirement account used to purchase the Notes or renders investment advice with respect to those assets and (2) such plan or retirement account is paying no more than adequate consideration for the Notes or (B) its acquisition and holding of the Notes is not prohibited by any such provisions or laws or is exempt from any such prohibition.

However, individual retirement accounts, individual retirement annuities and Keogh plans, as well as employee benefit plans that permit participants to direct the investment of their accounts, will not be permitted to purchase or hold the Notes if the account, plan or annuity is for the benefit of an employee of Citigroup Global Markets or a family member and the employee receives any compensation (such as, for example, an addition to bonus) based on the purchase of Notes by the account, plan or annuity.

You should refer to the section “ERISA Matters” in the pricing supplement related to this offering for more information.

If the Ending Value of the S&P 500 ^® Index is not available on the Valuation Date, the Calculation Agent may determine the Ending Value in accordance with the procedures set forth in the pricing supplement related to this offering. In addition, if the S&P 500 ^® Index is discontinued, the Calculation Agent may determine the Ending Value by reference to a successor index or, if no successor index is available, in accordance with the procedures last used to calculate the index prior to any such discontinuance. You should refer to the sections “Description of the Notes—Note Return Amount” and “—Discontinuance of the S&P 500 ^® Index” in the pricing supplement related to this offering for more information.

Citigroup Global Markets is an affiliate of Citigroup Funding. Accordingly, the offering will conform with the requirements set forth in Rule 2720 of the NASD Conduct Rules adopted by the of the Financial Industry Regulatory Authority.

Client accounts over which Citigroup Inc. or its subsidiaries have investment discretion are NOT permitted to purchase the Notes, either directly or indirectly.