Annual Report of Employee Stock Purchase/Savings Plan (Form 11-K)

11-K

    

    

1-14756

REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

Plan Participants and Plan Administrator of the Ameren Corporation Savings Investment Plan St. Louis, Missouri

Opinion on the Financial Statements

We have audited the accompanying statements of net assets available for benefits of Ameren Corporation Savings Investment Plan (the "Plan") as of December 31, 2025 and 2024, the related statements of changes in net assets available for benefits for the years then ended, and the related notes (collectively referred to as the "financial statements"). In our opinion, the financial statements present fairly, in all material respects, the net assets available for benefits of the Plan as of December 31, 2025 and 2024, 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.

Basis for Opinion

These financial statements are the responsibility of the Plan's management. Our responsibility is to express an opinion on the Plan's financial statements based on our audits. We are a public accounting firm registered with the Public Company Accounting Oversight Board (United States) ("PCAOB") and are required to be independent with respect to the Plan in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB.

We conducted our audits in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement, whether due to error or fraud. The Plan is not required to have, nor were we engaged to perform, an audit of its internal control over financial reporting. As part of our audits, we are required to obtain an understanding of internal control over financial reporting but not for the purpose of expressing an opinion on the effectiveness of the Plan's internal control over financial reporting. Accordingly, we express no such opinion.

Our audits included performing procedures to assess the risks of material misstatement of the financial statements, whether due to error or fraud, and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the financial statements. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the financial statements. We believe that our audits provide a reasonable basis for our opinion.

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Supplemental Information

The supplemental Schedule H, Line 4i - Schedule of Assets (Held at End of Year) as of December 31, 2025 has been subjected to audit p edures performed in conjunction with the audit of Ameren Corporation Savings Investment Plan financial statements. The supplemental schedule is the responsibility of the Plan's management. Our audit procedures included determining whether the information presented in the supplemental schedule reconciles to the financial statements or the underlying accounting and other records, as applicable, and performing procedures to test the completeness and accuracy of the information presented in the supplemental schedule. In forming our opinion on the supplemental schedule, we evaluated whether the supplemental schedule, including its form and content, is presented in conformity with the Department of Labor's Rules and Regulations for Reporting and Disclosure under the Employee Retirement Income Security Act of 1974. In our opinion, the supplemental schedule is fairly stated in all material respects in relation to the financial statements as a whole.

/s/ Crowe LLP

Crowe LLP

We have served as the Plan's auditor since 2014.

Oakbrook Terrace, Illinois

June 26, 2026

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Ameren Corporation

Savings Investment Plan

Statements of Net Assets Available for Benefits

December 31, 2025 and 2024

The accompanying notes are an integral part of these financial statements.

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Ameren Corporation

Savings Investment Plan

Statements of Changes in Net Assets Available for Benefits

Years Ended December 31, 2025 and 2024

The accompanying notes are an integral part of these financial statements.

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Ameren Corporation

Savings Investment Plan

Notes to Financial Statements

December 31, 2025 and 2024

General

The following is a summary of the various provisions of the Ameren Corporation Savings Investment Plan (the "Plan"). Participants should refer to the Summary Plan Description for the Plan for more complete information.

The Plan is a defined contribution plan. Its purpose is to provide employees eligible to participate (the "Participants") of Ameren Corporation (the "Company") and its wholly owned subsidiaries the opportunity to defer a portion of their 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 Ameren Administrative Committee has the authority and responsibility for the general administration of the Plan. Fidelity Management Trust Company ("Fidelity"), as Trustee, has the authority and responsibility to hold and protect the assets of the Plan in accordance with Plan provisions and with the Trust and Administrative Agreement.

Participation

All regular full-time employees are eligible to participate in the Plan upon employment. Part-time or temporary employees are eligible to participate in the Plan upon completion of a year of service with at least 1,000 hours of service; or effective January 1, 2021, if they have completed 500 hours of employment annually over any three consecutive year period that begins on or after January 1, 2021; or effective January 1, 2025 if they complete 500 hours of employment annually over any two consecutive year period that begins on or after January 1, 2023. Effective January 1, 2026, the Plan was amended to remove the one year of service requirement for eligibility.

Employees covered by a collective bargaining agreement ("CBA") are eligible to participate only if the CBA provides for such participation.

If employees do not make an election, nor within 30 days of employment, they are automatically enrolled at a 6% contribution rate, invested in a Target Date fund based upon the date at which the Participant is or will be age 65, and further enrolled in auto-escalation increasing their contribution 1% annually, with no cap on the annual increases. Employees may or make alternative elections at any time.

Contributions

Each year, Participants may contribute up to 100% of eligible compensation, as defined in the Plan, and subject to annual limitations imposed by the Code.

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Ameren Corporation

Savings Investment Plan

Notes to Financial Statements

December 31, 2025 and 2024

The Company makes an Employer Basic Matching Contribution plus an Employer Additional Matching Contribution in an amount e al to a percentage of the amount each 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 contributions depends on the Participant's employment classification and, for contract employees, is determined by the collective bargaining agreement with the specific union representing the Participants. The Company also makes Employer Basic Matching Contributions for Participants who contribute the IRS maximum before the end of the year and, as a result, do not receive the full match during such year.

The Plan permits annual contributions for all employees age 50 and older. For eligible employees, the additional contributions were limited to $7,500 in 2025 and 2024. The Company does not match contributions. Notwithstanding the foregoing, effective January 1, 2026, the Plan was amended to allow participants who attain ages during the Plan year a higher limit.

The Plan permits the Company to make an Additional Company Contribution for contract employees in compliance with a collective bargaining agreement with the specific union representing the Participants. Additional Company Contributions will always be 100% vested and nonforfeitable, and will otherwise be subject to the same distribution, loan and withdrawal restrictions as apply to Employer Basic Matching Contributions.

Participants direct the investment of their contributions and the Employer Basic Matching Contributions to his or her account to any of the investment options available under the Plan, including the Ameren Stock Fund. The Ameren Stock Fund is comprised primarily of Ameren common stock and a small position in a short-term liquidity investment. The Employer Additional Matching Contributions are invested in the Ameren Stock Fund. Participant contributions and Employer Basic Matching Contributions may be allocated to a single investment option or allocated in increments of one percent to any combination of investment options. Employer Additional Matching Contributions invested in the Ameren Stock Fund may be immediately reallocated to any of the other investment options available under the Plan at the participants' discretion. Investment elections may be changed daily.

At December 31, 2025, the Ameren Stock Fund held 3,742,606 shares of Company common stock with a fair value of $373,736,635 and shares of the Fidelity Institutional Money Market Government Portfolio with a fair value of $5,381,807. At December 31, 2024, the Ameren Stock Fund held 3,810,296 shares of Company common stock with a fair value of $339,649,785 and shares of the Fidelity Institutional Money Market Government Portfolio with a fair value of $5,085,186.

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.

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Ameren Corporation

Savings Investment Plan

Notes to Financial Statements

December 31, 2025 and 2024

Participant Accounts

Each Participant's account is credited with the Participant's contributions and an allocation of (a) the Company's matching contributions and (b) Plan earnings. Each Participant's account is charged with benefits paid, and an allocation of (a) Plan losses and (b) administrative expenses. Allocations are based on Participant contributions, eligible compensation, Participant account balances, or specific Participant transactions, as defined. The benefit to which the Participant is entitled is the benefit which can be provided from the Participant's account. Each Participant directs the investment of his or her account to any of the investment options available under the Plan.

The Plan imposes certain restrictions on participant directed investments into the Ameren Stock Fund. Allocations (other than the Employer Additional Matching Contributions) to the Ameren Stock Fund are limited to 20 percent for both contributions and existing balances. No more than 20 percent of contributions other than the Employer Additional Matching Contributions may be directed to the Ameren Stock Fund or, if rebalancing, the Ameren Stock Fund balance cannot exceed 20 percent of a participant's total account balance. If a participant's investments in the Ameren Stock Fund remain above 20 percent of his or her total account balance since September 1, 2019 (effective date of the restriction), then additional exchanges into the Ameren Stock Fund will not be permitted.

Notes Receivable from Participants

The Plan permits Participants to borrow from their accounts within the Plan. Participants may not have more than two loans outstanding at any time. 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 50% 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) each loan shall bear a reasonable interest rate as determined under policies established for the Plan and (5) such other rules and regulations as may be adopted by the Company. As of December 31, 2025 and 2024, the interest rates on participant loans ranged from 4.00 percent to 10.50 percent.

Vesting

The amounts in Participants' accounts, including Company contributions, are always fully vested.

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 after termination of employment. All distributions shall be in the form of cash except that Participants may elect to have his or her interest in the Ameren Stock Fund distributed in shares of Ameren common stock.

On December 29, 2022, The Consolidated Appropriations Act of 2023 was enacted. The Act includes the retirement provisions referred to as SECURE 2.0. Beginning in 2023, the SECURE 2.0 Act raised the age that a participant must begin taking required minimum distributions ("RMDs") to age 73. Effective for Participants who reached age 72 in 2023 the Plan began making RMDs no later than April 1, 2025.

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Ameren Corporation

Savings Investment Plan

Notes to Financial Statements

December 31, 2025 and 2024

Participants may withdraw certain 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 allows, at the discretion of the Company, participants of the former Union Electric Company Employee Stock Ownership Plan and the former Ameren Corporation Employee Stock Ownership Plan for Certain Employees of Central Illinois Public Service Company, to receive certain distributions prior to termination of employment.

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.

Basis of Accounting

The accompanying financial statements of the Plan are prepared on the accrual basis of accounting, except that benefit payments to Participants are recorded upon distribution.

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, the 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.

Investment Valuation and Income Recognition

All investments are presented at fair value, except for fully benefit-responsive investment contracts, which are reported at contract value, as of December 31, 2025 and 2024. Fair value is the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. See Note 3 for discussion of fair value measurements.

The Plan has direct investments in fully benefit-responsive investment contracts. Investments held by a defined contribution plan are required to be reported at fair value, except for fully benefit-responsive investment contracts. Contract value is the relevant measurement attribute for the portion of the net assets available for benefits of a defined contribution plan attributable to fully benefit-responsive investment contracts because contract value is the amount Participants normally would receive if they were to initiate permitted transactions under the terms of the Plan. Contract value represents contributions made under each contract, plus earnings, less participant withdrawals, and less administrative expenses.

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Ameren Corporation

Savings Investment Plan

Notes to Financial Statements

December 31, 2025 and 2024

Purchases and sales of securities are recorded on a trade date basis. Interest income is recorded on the accrual basis. Dividend income is recorded on the date. Net appreciation (depreciation) in fair value of investments includes the Plan's gains and losses on investments bought and as well as held during the year.

Notes Receivable from Participants

Notes receivable from Participants are measured at their unpaid principal balance plus any accrued but unpaid interest, with no allowance for credit losses, as repayments of principal and interest are received through payroll deductions and the notes are collateralized by the Participants' account balances. Delinquent participant loans are reclassified as distributions based upon the terms of the Plan document.

Administrative Expenses

Fees associated with administering the Plan are generally paid by the Plan. Trustee and recordkeeping fees are primarily paid via (1) flat dollar fees that are assessed to all Participants quarterly, and (2) fees accrued in investment funds that are separately managed accounts (versus commingled funds). Also, revenue sharing payments that Fidelity receives from mutual funds are allocated to Participant accounts quarterly.

Risks and Uncertainties

Investments are exposed to various risks, such as interest rate, market, and credit risks, which includes glob events such as geopolitical conflicts and pandemics. Due to the level of risk associated with certain investments and the level of uncertainty related to changes in the value of investments, it is at least reasonably possible that changes in risks in the near term could materially affect the Participants' account balances and the amounts reported in the Statements of Net Assets Available for Benefits.

Concentrations

Company common stock comprised 11% of investments at December 31, 2025 and 2024, respectively.

The authoritative guidance issued by the Financial Accounting Standards Board (the "FASB") regarding fair value measurement provides a framework for measuring fair value for all assets and liabilities that are measured and reported at fair value. The guidance defines fair value as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Certain assumptions that market participants would use in pricing the asset or liability, including assumptions about risk or the risks inherent in the inputs to the valuation, were used in the valuation process. Inputs to valuation can be readily observable, market corroborated, or unobservable. Valuation techniques that maximize the use of observable inputs and minimize the use of unobservable inputs were used. The provisions also establish a fair value hierarchy that prioritizes the inputs used to measure fair value. All financial assets and liabilities carried at fair value were classified in one of the following three hierarchy levels:

Level 1: Inputs based on quoted prices in active markets for identical assets or liabilities that the Plan has the ability to access at the reporting date.

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Ameren Corporation

Savings Investment Plan

Notes to Financial Statements

December 31, 2025 and 2024

Level 2: Inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly. Inputs to the valuation methodology include:

Level 3: Inputs to the valuation methodology that are unobservable and significant to the fair value measurement.

The Plan does not hold any investments requiring Level 3 measurements, and there have not been any transfers between measurement input levels in 2025 or 2024.

The asset's or liability's fair value measurement level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement.

The following is a description of the valuation methodologies used for assets measured at fair value. There have been no changes in the methodologies used during 2025.

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Ameren Corporation

Savings Investment Plan

Notes to Financial Statements

December 31, 2025 and 2024

The Plan holds investments in a separately managed stable value account that is managed by Galliard Capital Management. The separately managed account holds (1) an investment in the Short-Term Investment Fund II (SEI Trust Company sponsored CIT), and (2) a portfolio of investment contracts, valued at $214,677,784 and $232,921,178 at December 31, 2025 and 2024, respectively. The investment contracts meet the fully benefit-responsive investment criteria and therefore are reported at contract value. Contract value is the relevant measure for fully benefit-responsive investment contracts because this is the amount received by Participants if they were to initiate permitted transactions under the terms of the Plan. Contract value represents contributions made under each contract, plus earnings, less participant withdrawals, and less administrative expenses.

The investment contracts (also referred to herein as "wrapper contracts") are issued by the following insurance companies (also referred to herein as "contract issuer(s)"):

As of December 31, 2025 and 2024, the underlying investments of the AGL, Mass Mutual, Transamerica, Voya, and Met Life contracts are holdings in collective trust funds. The investment contracts include wrapper contracts, which are agreements for the contract issuer to make payments to the Plan under certain circumstances. The wrapper contracts typically include certain conditions and limitations on the underlying assets owned by the Plan. The wrapper contracts are designed to accrue interest based on crediting rates calculated under the terms of the wrapper contracts, and also provide a guarantee that the crediting rate will not fall below zero percent. Cash flow volatility (for example, timing of benefit payments) as well as asset underperformance are passed through to the Plan through adjustments to future wrapper contract crediting rates. Formulas are provided in each contract that adjusts renewal crediting rates to recognize the difference between the fair value of the underlying assets and the contract value. Crediting rates are reset at least quarterly.

The Plan's ability to receive amounts due in accordance with fully benefit-responsive investment contracts is dependent on the third-party contract issuer's ability to meet its financial obligations. The contract issuer's ability to meet its contractual obligations may be affected by future economic and regulatory developments.

Certain events might limit the ability of the Plan to transact at contract value. Investment contracts generally provide for withdrawals associated with certain events which are not in the ordinary course of operations. These withdrawals may be paid with a market value adjustment applied to the withdrawal as defined in the investment contract. Each contract issuer specifies the events which may trigger a market value adjustment; such events may include all or a portion of the following:

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Ameren Corporation

Savings Investment Plan

Notes to Financial Statements

December 31, 2025 and 2024

No events are probable of occurring that might limit the ability of the Plan to transact at contract value on behalf of the Participants.

These investment contracts are evergreen contracts and contain termination provisions, allowing the contract issuer to terminate with notice, at any time at fair value, and providing for automatic termination of the investment contract if the contract value or the fair value of the underlying portfolio equals zero. The contract issuer is obligated to pay the excess contract value when the fair value is below contract value at the time of termination and termination was caused by certain events including fraud or misconduct related to the investment contracts, such as material misrepresentations. In addition, if the Plan defaults in its obligations under the investment contract (including the contract issuer's determination that the agreement constitutes a prohibited transaction as defined under ERISA), and such default is not corrected within the time permitted by the investment contract, then the investment contract may be terminated by the contract issuer and the Plan will receive the fair value as of the date of termination.

are defined under Department of Labor regulations as any fiduciary of the Plan, any party rendering service to the Plan, the employer, and certain others.

At December 31, 2025, the Plan held 3,742,606 shares of Company common stock with a cost and fair value of $200,496,899 and $373,736,635, respectively. During 2025, the Plan purchased 139,356 shares at a cost of $13,742,718 and sold 207,046 shares valued at $20,589,229.

At December 31, 2024, the Plan held 3,810,296 shares of Company common stock with a cost and fair value of $197,643,166 and $339,649,785, respectively. During 2024, the Plan purchased 147,522 shares at a cost of $11,485,245 and sold 323,016 shares valued at $25,646,132.

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Ameren Corporation

Savings Investment Plan

Notes to Financial Statements

December 31, 2025 and 2024

For the year ended December 31, 2025, dividend income and realized gains from the sale of Company common stock was $10,649,834 and $9,700,245, respectively. For the year ended December 31, 2024, dividend income and realized gains from the sale of Company common stock was $10,391,016 and $9,090,944, respectively.

At December 31, 2025 and 2024, the Plan held shares in the Fidelity Institutional Money Market Government Portfolio. This portfolio is managed by the Trustee, and therefore, qualifies as transactions. Notes receivable from Participants also reflect transactions.

Fees paid by the Plan to the Trustee for recordkeeping, trust services, and advisory services were $1,402,551 and $1,390,801 for the years ended December 31, 2025 and 2024, respectively.

Fees paid to and investments issued by various Plan investment managers or affiliates of Plan investment managers also reflect transactions.

These transactions are allowable transactions under Section 408(b)(8) of ERISA.

The following is a reconciliation of net assets available for benefits per the financial statements to the Form 5500 at December 31, 2025 and 2024:

Deemed distributions of notes receivable from Participants, resulting from defaults of notes receivable from Participants, are no longer considered assets of the Plan with respect to Form 5500 filings.

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Ameren Corporation

Savings Investment Plan

Notes to Financial Statements

December 31, 2025 and 2024

The following is a reconciliation of net increase in net assets available for benefits per the financial statements to net income per the Form 5500 for the year ended December 31, 2025:

The Company obtained a determination letter dated January 12, 2018, in which the Internal Revenue Service stated that the Plan was in compliance with the applicable requirements of the Code. Although the Plan has been amended since receiving this determination letter, the Plan's administrator believes that the Plan is designed and is currently being operated in compliance with the applicable requirements of the Code.

Accounting principles generally accepted in the United States of America require Plan management to evaluate tax positions taken by the Plan and recognize a tax liability (or asset) if the Plan has taken an uncertain position that more likely than not would not be sustained upon examination by the Internal Revenue Service. The Plan administrator has analyzed the tax positions taken by the Plan, and has concluded that as of December 31, 2025 and 2024, there are no uncertain positions taken or expected to be taken that would require recognition of a liability (or asset) or disclosure in the financial statements. The Plan is subject to routine audits by taxing jurisdictions; however, there are currently no audits for any tax periods in progress. The Plan administrator believes it is no longer subject to income tax examinations for years prior to 2022.

There were no subsequent events identified through June 26, 2026, the date the financial statements were issued.

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Ameren Corporation Savings Investment Plan

SCHEDULE H, Line 4i - SCHEDULE OF ASSETS (HELD AT END OF YEAR)

December 31, 2025

Name of plan sponsor: Ameren Corporation

Employer identification number: 43-1723446

Three-digit plan number: 003

(d) cost: Investment is participant directed, therefore historical cost is not required.

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Ameren Corporation Savings Investment Plan

SCHEDULE H, Line 4i - SCHEDULE OF ASSETS (HELD AT END OF YEAR)

December 31, 2025

Name of plan sponsor: Ameren Corporation

Employer identification number: 43-1723446

Three-digit plan number: 003

(d) cost: Investment is participant directed, therefore historical cost is not required.

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Ameren Corporation Savings Investment Plan

SCHEDULE H, Line 4i - SCHEDULE OF ASSETS (HELD AT END OF YEAR)

December 31, 2025

Name of plan sponsor: Ameren Corporation

Employer identification number: 43-1723446

Three-digit plan number: 003

(d) cost: Investment is participant directed, therefore historical cost is not required.

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