UNITED STATES SECURITIES AND EXCHANGE COMMISISION WASHINGTON, DC 20549 FORM 11-K (X) ANNUAL REPORT PURSUANT TO SECTION 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 FOR THE FISCAL YEAR ENDED DECEMBER 31, 2002 OR ( ) TRANSITION REPORT PURSUANT TO SECTION 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to COMMISSION FILE NUMBER 1-14756 A. Full title of the plan and the address of the plan, if different from that of the issuer named below: AMEREN CORPORATION SAVINGS INVESTMENT PLAN B. Name of issuer of securities held pursuant to the plan and the address of its principal executive office: Ameren Corporation 1901 Chouteau Avenue St. Louis, Missouri 63103 Ameren Corporation Savings Investment Plan Financial Statements and Additional Information December 31, 2002 and 2001 Ameren Corporation Savings Investment Plan Contents December 31, 2002 and 2001 -------------------------------------------------------------------------------- Page(s) Report of Independent Auditors................................................1 Statements of Net Assets Available for Benefits...............................2 Statements of Changes in Net Assets Available for Benefits....................3 Notes to Financial Statements..............................................4-10 Additional Information* Schedule I: Schedule of Assets (Held at End of Year)...................11 * Other schedules required by 29 CFR 2520.103-10 of the Department of Labor's Rules and Regulations for Reporting and Disclosure under ERISA have been omitted because they are not applicable. Report of Independent Auditors To the Participants and Administrator of the Ameren Corporation Savings Investment Plan In our opinion, the accompanying statements of net assets available for benefits and the related statements of changes in net assets available for benefits present fairly, in all material respects, the net assets available for benefits of the Ameren Corporation Savings Investment Plan (the "Plan") at December 31, 2002 and 2001, and the changes in net assets available for benefits for the years then ended in conformity with accounting principles generally accepted in the United States of America. These financial statements are the responsibility of the Plan's management; our responsibility is to express an opinion on these financial statements based on our audits. We conducted our audits of these statements in accordance with auditing standards generally accepted in the United States of America, which require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement. An audit includes examining, on a test basis, evidence supporting the amounts and disclosures in the financial statements, assessing the accounting principles used and significant estimates made by management, and evaluating the overall financial statement presentation. We believe that our audits provide a reasonable basis for our opinion. Our audits were conducted for the purpose of forming an opinion on the basic financial statements taken as a whole. The supplemental schedule of assets (held at end of year) is presented for the purpose of additional analysis and is not a required part of the basic financial statements but is supplementary information required by the Department of Labor's Rules and Regulations for Reporting and Disclosure under the Employee Retirement Income Security Act of 1974. This supplemental schedule is the responsibility of the Plan's management. The supplemental schedule has been subjected to the auditing procedures applied in the audits of the basic financial statements and, in our opinion, is fairly stated in all material respects in relation to the basic financial statements taken as a whole. The schedule of assets (held at end of year) that accompanies the Plan's financial statements does not disclose the historical cost of certain nonparticipant-directed Plan assets held by the Plan's trustee. Disclosure of this information is required by the Department of Labor's Rules and Regulations for Reporting and Disclosure under the Employee Retirement Income Security Act of 1974. /s/ PricewaterhouseCoopers LLP PricewaterhouseCoopers LLP St. Louis, Missouri June 20, 2003 1 Ameren Corporation Savings Investment Plan Statements of Net Assets Available for Benefits December 31, 2002 and 2001 -------------------------------------------------------------------------------- 2002 2001 Assets Investments (Note 3) $626,996,779 $683,613,115 Cash 2,443 388,626 Receivables Participant contributions 1,544,606 1,353,420 Employer contributions 626,752 568,020 Dividends and interest 477,104 35,356 Due from broker for securities sold - 1,014,395 ------------ ------------ Total receivables 2,648,462 2,971,191 Total assets $629,647,684 $686,972,932 ------------ ------------ Liabilities Accrued expenses 23,525 - ------------ ------------ Net assets available for benefits $629,624,159 $686,972,932 ============ ============ The accompanying notes are an integral part of these financial statements. 2 Ameren Corporation Savings Investment Plan Statements of Changes in Net Assets Available for Benefits For the Years Ended December 31, 2002 and 2001 -------------------------------------------------------------------------------- 2002 2001 Investment income (loss) Interest and dividends $ 21,086,084 $ 15,069,266 Net depreciation in fair value of investments (93,753,190) (49,526,185) -------------- -------------- (72,667,106) (34,456,919) -------------- -------------- Participant contributions 38,901,181 39,907,028 Employer contributions 13,857,557 12,511,947 -------------- -------------- 52,758,738 52,418,975 -------------- -------------- Plan transfer in (Note 1) - 20,211,328 -------------- -------------- Benefits and expenses Benefits paid to participants 37,311,364 36,247,614 Administrative expenses 129,041 80,177 -------------- -------------- 37,440,405 36,327,791 -------------- -------------- Net (decrease) increase (57,348,773) 1,845,593 Net assets available for benefits Beginning of year 686,972,932 685,127,339 -------------- -------------- End of year $ 629,624,159 $ 686,972,932 ============== ============== The accompanying notes are an integral part of these financial statements. 3 Ameren Corporation Savings Investment Plan Notes to Financial Statements December 31, 2002 and 2001 -------------------------------------------------------------------------------- 1. Description of the Plan General The following is a brief summary of the various provisions of the Ameren Corporation (the "Company") Savings Investment Plan (the "Plan"). Participants should refer to the Plan document for more complete information. The Plan's purpose is to provide certain management and contract employees of the Company and its wholly owned subsidiaries (the "Participant") the option to defer a portion of their annual base compensation for Federal income tax purposes in accordance with Section 401(k) of the Internal Revenue Code (the "Code"). The Plan is subject to certain provisions of the Employee Retirement Income Security Act of 1974 ("ERISA"), as amended, and regulations of the Securities and Exchange Commission. The Company serves as sponsor of the Plan, and, consequently, has the authority to amend or terminate the Plan subject to certain restrictions. The Board of Directors of the Company has the authority and responsibility for the general administration of the Plan. The Northern Trust Company, as Trustee, has the authority and responsibility to hold and protect the assets of the Plan in accordance with Plan provisions and the separate Trust Agreement. Effective January 1, 2001, the Plan was amended to merge the assets of the Ameren Corporation Employee Stock Ownership Plan for Certain Employees of CIPS into the Plan. The assets transferred into the Plan consisted of 436,088 shares of Ameren stock as of the date of the transfer with a fair market value of $20,211,328. Effective December 2001, when dividends are paid on shares of Company common stock held in the Ameren Common Stock Fund of the Plan, these dividends are used to purchase newly issued shares of Company common stock at fair market value instead of shares being purchased in the open market. Effective June 1, 2002, with the passage of the Economic Growth and Tax Relief Reconciliation Act ("EGTRRA"), the Plan was changed to designate the Ameren Common Stock Fund of the Plan as an Employee Stock Ownership Plan and to allow all Participants a choice between dividend reinvestment and dividend payment on their various Employee Stock Ownership Plan accounts. Effective July 1, 2002, the Plan was also changed to allow management employees to contribute up to 50 percent of their base pay to the Plan subject to ERISA limitation requirements, and the "catch up" contribution provision of EGTRRA for all employees age 50 and older was implemented as well. Participation The Plan covers substantially all employees of the Company except contract employees covered by a collective bargaining agreement between AmerenCIPS Local 702 IBEW or AmerenCIPS Local 148 IUOE and the Company. Effective July 1, 2001, the Plan was amended to allow AmerenCIPS Local 148 (Clerical) to participate in the Plan. All regular full time employees are eligible to participate upon employment. Participation by eligible employees is voluntary. 4 Ameren Corporation Savings Investment Plan Notes to Financial Statements December 31, 2002 and 2001 -------------------------------------------------------------------------------- Contributions Contract Participants may contribute from one percent to 15 percent of their base compensation to the Plan through payroll deductions. Management Participants may contribute from one percent to 50 percent of their base compensation to the Plan through payroll deductions. Participant contributions are subject to annual limitations imposed by the Code. The Company will make an Employer Basic Matching Contribution plus an Employer Additional Matching Contribution in an amount equal to a percent of the amount the Participant contributes to the Plan, up to a certain maximum percentage of the Participant's compensation that he or she elects to contribute to the Plan each year. The amount of Company matching contribution depends on the Participant's employment classification and for contract employees as determined by the collective bargaining agreement with the specific union representing the employees. A portion of Company matching contributions is invested in the Ameren Common Stock Fund. All Company contributions are made to the extent sufficient earnings are available, as described in the Plan document. Participants direct their basic contributions and the Company's basic matching contributions by electing that such contributions be placed in a single investment fund or allocated in increments of one percent to any combination of investment funds. Such fund allocation elections may be changed daily. Earnings derived from the assets of any investment fund are reinvested in the fund to which they relate. Participants may elect daily to reallocate, by actual dollar or percentage in one percent increments, the value of their accounts between funds. Pending investment of the assets into any investment fund, the Trustee may temporarily make certain short-term investments. Participant Loans The Plan permits Participants to borrow from their accounts within the Plan. Such borrowings may be made subject to the following: (1) the minimum amount of the loan is $1,000, (2) the amount of the loan may not exceed the lesser of $50,000 or fifty percent of the vested amount in the Participant's account, (3) the loan will bear a fixed interest rate and repayments will be made through mutual agreement subject to certain statutory repayment time limits, (4) the fixed interest rate will be equal to the "corporate base rate of interest" as announced by the Trustee plus one percent, and (5) such other rules and regulations as may be adopted by the Company. At December 31, 2002 and 2001, the interest rates on participant loans ranged from 5.25 percent to 10.5 percent and 7 percent to 10.5 percent, respectively. Vesting The amounts in Participants' accounts, including Company contributions, are fully vested at all times. 5 Ameren Corporation Savings Investment Plan Notes to Financial Statements December 31, 2002 and 2001 -------------------------------------------------------------------------------- Payment of Benefits The total amount of a Participant's account shall be distributed to the Participant according to one of the options as described in the Plan document and as elected by the Participant. A Participant whose account balance is $5,000 or greater may defer distribution until December 31 of the year they attain age 70 1/2 but no later than April 1 of the year following the Participant's attaining age 70 1/2. If the balance of the account is less than $5,000, the distribution shall be made no later than 120 days after close of the Plan year. All distributions shall be in the form of cash except that Participants may elect to have his or her interest in the Ameren Common Stock Fund, if applicable, distributed in shares of Ameren common stock. Participants may withdraw certain basic contributions, rollover contributions and related earnings thereon upon reaching age 59 1/2, in the event of total disability or financial hardship as defined by the Plan or the Code. For purposes of distributions, the Participant's account value will be determined as of the last business day coincident with or immediately preceding the day of distribution. Contributions to the Plan and investment income thereon are taxable to Participants upon distribution pursuant to the rules provided for under the Plan and the Code. The Plan also provides, to participants of the former Union Electric Company Employee Stock Ownership Plan and the former Ameren Corporation Employee Stock Ownership Plan for Certain Employees of CIPS and at the discretion of the Company, for distribution prior to termination of employment of (a) all or a portion of a Participant's account balance acquired at least 84 months prior to a distribution and (b) any portion of a Participant's account balance acquired by dividends or other income. Plan Termination The Company intends to continue the Plan indefinitely. However, the Company may at any time and for any reason, subject to ERISA and Internal Revenue Service regulations, suspend or terminate the Plan provided that such action does not retroactively adversely affect the rights of any Participant under the Plan. 2. Summary of Significant Accounting Policies Basis of Accounting The accompanying financial statements of the Plan are prepared on the accrual basis of accounting. Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of changes in net assets available for benefits during the reporting period. Actual results could differ from those estimates. 6 Ameren Corporation Savings Investment Plan Notes to Financial Statements December 31, 2002 and 2001 -------------------------------------------------------------------------------- Investments All investments are presented at fair value as of December 31, 2002 and 2001. The fair value of the Ameren Common Stock Fund was determined using year-end published market prices. Investments in equity securities and bonds are valued at net asset market value including accrued income on the last business day of each year. Investments in the Northern Trust Company's Short-term Fund and the T. Rowe Price Stable Value Common Trust Fund are valued at cost plus accrued income, which approximates market. Participant loans are valued at cost, which approximates fair market value. Investment securities are exposed to various risks, such as interest rate, market, and credit. Due to the level of risk associated with certain investment securities and the level of uncertainty related to changes in the value of investment securities, it is at least reasonably possible that changes in risks in the near term could materially affect the amounts reported in the Statement of Net Assets Available for Benefits. Income Interest income is recorded on the accrual basis. Dividend income is recorded on the ex-dividend date. Gains and losses on security transactions are recorded on the trade date. Net unrealized appreciation or depreciation for the year is reflected in net depreciation in fair value of investments on the Statement of Changes in Net Assets Available for Benefits. Expenses Trustee fees incurred in administering the Plan are charged to the Plan. Benefit Payments Benefit payments are recorded when paid. 7 Ameren Corporation Savings Investment Plan Notes to Financial Statements December 31, 2002 and 2001 -------------------------------------------------------------------------------- 3. Investments The following table presents investments of the Plan at December 31, 2002 and 2001, respectively: 2002 2001 Investments at Fair Value as Determined By Quoted Market Price Common Stock Ameren Corporation, $.01 par value($179,034,216 $180,505,606 Managed Equity Funds MSIF Trust Fund 84,001,696 124,134,320 Barclays Global Investors Equity Index Fund 35,725,072 46,661,437 Vanguard US Growth Fund 24,243,926 39,883,621 Washington Mutual Investors Fund 73,904,236 87,789,899 Vanguard Asset Allocation Fund 55,730,317 68,541,101 Vanguard Extended Market Index Fund 6,650,011 5,349,502 Managed International Equity Fund American Funds Group Europacific Growth Fund 18,820,977 21,609,653 Investments at Estimated Fair Value T. Rowe Price Stable Value Common Trust Fund 109,290,844 85,156,018 MFO Pimco Funds 18,220,489 4,522,490 Northern Trust Company's Short-Term Investment Fund 3,904,650 3,184,174 Participant Loans 17,470,345 16,275,294 ------------ ------------ Total investments $626,996,779 $683,613,115 ============ ============ 8 Ameren Corporation Savings Investment Plan Notes to Financial Statements December 31, 2002 and 2001 -------------------------------------------------------------------------------- During 2002 and 2001, the Plan's investments (including investments bought, sold, and held during the year) depreciated in value as follows: 2002 2001 Investments at Fair Value as Determined By Quoted Market Price Managed Fund Investments $(91,691,064) $(33,673,621) Ameren Common Stock Fund (2,662,341) (15,856,027) ------------- ------------- Net change in fair value (94,353,405) (49,529,648) Investments at Estimated Fair Value Short-term Investments 600,215 3,463 ------------- ------------- Net change in fair value $(93,753,190) $(49,526,185) ============= ============= 4. Nonparticipant-Directed Investments Information about the net assets and the significant components of the changes in net assets relating to the nonparticipant-directed investments at and for the years ended December 31, 2002 and 2001, is as follows: 2002 2001 Net assets Ameren Common Stock Fund $ 40,209,751 $ 36,441,059 Employer contributions receivable 182,310 332,379 Changes in net assets Dividends 2,304,531 1,985,449 Net appreciation (depreciation) in fair value of investments 703,956 (2,731,877) Employer contributions 4,978,154 4,426,367 Benefits paid to participants 971,143 583,065 5. Transactions with Parties-in-Interest At December 31, 2002, the Plan held Company common stock with a cost and market value of $142,754,115 and $179,034,216, respectively. During 2002, the Plan purchased shares at a cost of $25,044,373 and sold shares valued at $20,945,271. At December 31, 2001, the Plan held Company common stock with a cost and market value of $135,847,679 and $180,505,606, respectively. During 2001, the Plan purchased shares at a cost of $17,671,216 and sold shares valued at $6,327,522. 9 Ameren Corporation Savings Investment Plan Notes to Financial Statements December 31, 2002 and 2001 -------------------------------------------------------------------------------- The Plan held $3,904,650 and $3,184,174 in Northern Trust Company's Collective Short-Term Investment Fund at December 31, 2002 and 2001, respectively, which is managed by an affiliate of the Trustee. These transactions are allowable party-in-interest transactions under Section 408(b)(8) of the ERISA regulations. 6. Reconciliation of Financial Statements to Form 5500 The following is a reconciliation of net assets available for benefits per the financial statements to the Form 5500 at December 31, 2002 and 2001: 2002 2001 Net assets available for benefits per the financial statements $ 629,624,159 $ 686,972,932 Amounts allocated to withdrawing Participants (213,431) (428,138) -------------- -------------- Net assets available for benefits per the Form 5500 $ 629,410,728 $ 686,544,794 ============== ============== The following is a reconciliation of benefits paid to Participants per the financial statements to the Form 5500 for the years ended December 31, 2002 and 2001: 2002 2001 Benefits paid to Participants per the financial statements $ 37,311,364 $ 36,247,614 Add: Amounts allocated to withdrawing Participants during the current year 213,431 428,138 Less: Amounts allocated to withdrawing Participants during the prior year (428,138) (1,370,831) -------------- ------------- Benefits paid to Participants per the Form 5500 $ 37,096,657 $ 35,304,921 ============== ============= Amounts allocated to withdrawing Participants are recorded on the Form 5500 for benefit claims that have been processed and approved for payment prior to December 31, 2002 and 2001, as applicable, but not yet paid as of that date. 7. Federal Income Tax Status The Plan obtained its latest determination letter July 31, 2001, in which the Internal Revenue Service stated that the Plan was in compliance with the applicable requirements of the Code. The Company believes that the Plan currently is designed and being operated in compliance with the applicable requirements of the Code and, therefore, the Plan continues to qualify under Section 401(a) and the related trust continues to be tax-exempt as of December 31, 2002. Therefore, no provision for income taxes has been included in the Plan's financial statements. 10 Ameren Corporation Savings Investment Plan Schedule of Assets (Held at End of Year) December 31, 2002 Schedule I ------------------------------------------------------------------------------------------------------------------------ (a) (b) (c) (e) Description of investment including maturity Identity of issue, borrower, lessor, or similar date, rate of interest,collateral, par, or maturity Current party value value Massachusetts Funds MSIF Trust Fund $ 84,001,696 Barclays Global Investment Funds, Inc. Barclays Global Investors Equity Index Fund 35,725,072 The American Funds Group Europacific Growth Fund 18,820,977 Vanguard Group Vanguard US Growth Fund 24,243,926 Washington Mutual Investments Washington Mutual Investors Fund 73,904,236 Vanguard Group Vanguard Asset Allocation Fund 55,730,317 Vanguard Group Vanguard Extended Market Index Fund 6,650,011 * Northern Trust Company Short-term Investment Fund 3,904,650 T. Rowe Price Stable Asset Management, Inc. T. Rowe Price Stable Value Common Trust Fund 109,290,844 * Ameren Corporation Ameren Common Stock Fund 179,034,216 Pacific Investment Management Company MFO Pimco Funds 18,220,489 ** Participants Participant Loans 17,470,345 ------------ $626,996,779 ============ * Investment represents allowable transaction with a party-in-interest ** Interest rates vary from 5.25 percent to 10.5 percent and loan maturity dates extend from January 2001 through December 2009. Note: Information pertaining to column (d) was not available for nonparticipant-directed investments, and was omitted for participant-directed investments because it was not applicable. 11 SIGNATURES The Plan. Pursuant to the requirements of the Securities Exchange Act of 1934, the trustees (or other persons who administer the employee benefit plan) have duly caused this annual report to be signed on its behalf by the undersigned hereunto duly authorized. AMEREN CORPORATION SAVINGS INVESTMENT PLAN AMEREN SERVICES COMPANY (Administrator) By /s/ Donna K. Martin ------------------------------ Donna K. Martin Vice President June 30, 2003 EXHIBIT INDEX Exhibit No. Description ----------- ----------- 23 Consent of Independent Auditors 99.1 Certificate of Plan Administrator required by Section 1350 of Chapter 63 of Title 18 of the United States Code (Section 906 of the Sarbanes-Oxley Act of 2002). 99.2 Certificate of Chief Financial Officer required by Section 1350 of Chapter 63 of Title 18 of the United States Code (Section 906 of the Sarbanes-Oxley Act of 2002). 12 Investments that represent 5 percent or more of the Plan's net assets. Nonparticipant-directed portion is $40,209,751, and $36,441,059 at December 31, 2002 and 2001, respectively.