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Income Taxes | 12 Months Ended
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Dec. 31, 2025
Income Tax Disclosure [Abstract] |
INCOME TAXES | INCOME TAXES IRA The IRA was enacted in August 2022, and includes various income tax provisions, among other things. The law extends federal production and investment tax credits for projects beginning construction through 2024 and allows for a 10% adder to the production and investment tax credits for siting projects at existing energy communities as defined in the law, which includes sites previously used for coal-fired generation. The law also creates production and investment tax credits for projects beginning construction after 2024. The production and investment tax credits will apply to renewable energy production and investments, along with certain nuclear energy production. See the OBBBA below for additional information on revisions to the production and investment tax credits. The law allows for transferability, subject to revisions made by the OBBBA discussed below, to an unrelated party for cash of up to 100% of certain tax credits generated after 2022. In addition, the law imposes a 15% minimum tax on adjusted financial statement income, as defined in the law, for corporations whose average annual adjusted financial statement income exceeds $1 billion for three consecutive preceding tax years. Once a corporation exceeds this three-year average annual adjusted financial statement income threshold, it will be subject to the minimum tax for all future tax years. Additional regulations, interpretations, amendments, or technical corrections to or in connection with the IRA have been and are expected to be issued by the IRS or United States Department of Treasury, which may impact the timing of when the 15% minimum tax becomes applicable for Ameren. OBBBA The OBBBA was enacted in July 2025 and includes various income tax provisions, among other things. The OBBBA modified provisions of the IRA related to production and investment tax credits. The new law maintains production and investment tax credits for solar and wind projects that begin construction within one year of the OBBBA’s enactment and are placed in-service by the end of 2030. Projects that begin construction after one year from enactment of the OBBBA but are placed in service by the end of 2027 also remain eligible. The law provides investment tax credits for battery storage projects that begin construction by the end of 2033, which phase out by the end of 2035. Renewable energy projects that begin construction in 2026 and beyond that use a certain threshold percentage of materials from prohibited foreign entities, as defined in the OBBBA, are not eligible for the tax credits. Production tax credits associated with nuclear generation remain unchanged from the IRA and phase out by the end of 2032. Furthermore, the new law continues to allow for transferability of the production and investment tax credits to an unrelated party for cash but such credits are restricted from being transferred to specified foreign entities, as defined in the OBBBA. Ameren did not have any material impacts on its results of operations, financial position, and liquidity in 2025 related to the OBBBA. Implementation of the OBBBA provisions is subject to additional guidance, regulations, interpretations, amendments, or technical corrections that may be issued by the IRS or United States Department of Treasury. Ameren will continue to monitor and assess any impacts related to the OBBBA. The following table presents the principal reasons for the difference between the effective income tax expense and rate and the federal statutory corporate income tax expense and rate for the years ended December 31, 2025, 2024, and 2023:
| 2025 | 2024 | 2023
| Amount |  | Effective Tax Rate | Amount |  | Effective Tax Rate | Amount |  | Effective Tax Rate
Ameren |  |  |  |  |  |  |  |  |
Federal statutory corporate income tax expense and rate | $ | 335 |  |  | 21 | % | $ | 267 |  |  | 21 | % | $ | 282 |  |  | 21 | %
State and local taxes, net of federal income tax(a) | 74 |  |  | 5 |  | 61 |  |  | 5 |  | 64 |  |  | 5 |
Tax credits |  |  |  |  |  |  |  |  |
Renewable energy tax credits(b) | (61) |  |  | (4) |  | (117) |  |  | (9) |  | (52) |  |  | (4) |
Other | (3) |  |  | — |  | (7) |  |  | — |  | (6) |  |  | — |
Changes in valuation allowances | — |  |  | — |  | (4) |  |  | — |  | 5 |  |  | — |
Nontaxable or nondeductible items | (2) |  |  | — |  | 1 |  |  | — |  | (5) |  |  | — |
Other adjustments |  |  |  |  |  |  |  |  |
Amortization of excess deferred income taxes(c) | (107) |  |  | (7) |  | (112) |  |  | (9) |  | (98) |  |  | (8) |
Revaluation of excess deferred income taxes(d) | (86) |  |  | (5) |  | — |  |  | — |  | — |  |  | — |
Depreciation differences | (14) |  |  | (1) |  | (8) |  |  | (1) |  | (7) |  |  | — |
Other | — |  |  | — |  | 2 |  |  | — |  | — |  |  | — |
Effective income tax expense and rate | $ | 136 |  |  | 9 | % | $ | 83 |  |  | 7 | % | $ | 183 |  |  | 14 | %
Ameren Missouri |  |  |  |  |  |  |  |  |
Federal statutory corporate income tax expense and rate | $ | 166 |  |  | 21 | % | $ | 100 |  |  | 21 | % | $ | 113 |  |  | 21 | %
State and local taxes, net of federal income tax(a) | 21 |  |  | 3 |  | 13 |  |  | 3 |  | 14 |  |  | 3 |
Tax credits |  |  |  |  |  |  |  |  |
Renewable energy tax credits(b) | (61) |  |  | (8) |  | (113) |  |  | (24) |  | (49) |  |  | (10) |
Other | (3) |  |  | — |  | (4) |  |  | (1) |  | (5) |  |  | (1) |
Nontaxable or nondeductible items | 1 |  |  | — |  | 1 |  |  | — |  | (1) |  |  | — |
Other adjustments |  |  |  |  |  |  |  |  |
Amortization of excess deferred income taxes(c) | (75) |  |  | (10) |  | (79) |  |  | (17) |  | (80) |  |  | (15) |
Depreciation differences | (6) |  |  | (1) |  | (5) |  |  | — |  | — |  |  | — |
Effective income tax expense (benefit) and rate | $ | 43 |  |  | 5 | % | (87) |  |  | (18) | % | $ | (8) |  |  | (2) | %
Ameren Illinois |  |  |  |  |  |  |  |  |
Federal statutory corporate income tax expense and rate | $ | 187 |  |  | 21 | % | $ | 171 |  |  | 21 | % | $ | 172 |  |  | 21 | %
State and local taxes, net of federal income tax(a) | 66 |  |  | 7 |  | 62 |  |  | 7 |  | 61 |  |  | 7 |
Tax credits |  |  |  |  |  |  |  |  |
Renewable energy tax credits | — |  |  | — |  | (3) |  |  | — |  | — |  |  | — |
Other | (1) |  |  | — |  | (2) |  |  | — |  | (1) |  |  | — |
Nontaxable or nondeductible items | (1) |  |  | — |  | — |  |  | — |  | (1) |  |  | — |
Other adjustments |  |  |  |  |  |  |  |  |
Amortization of excess deferred income taxes(c) | (31) |  |  | (3) |  | (32) |  |  | (4) |  | (17) |  |  | (2) |
Revaluation of excess deferred income taxes(d) | (61) |  |  | (7) |  | — |  |  | — |  | — |  |  | — |
Depreciation differences | (9) |  |  | (1) |  | (3) |  |  | — |  | (5) |  |  | — |
Other | 3 |  |  | — |  | — |  |  | — |  | — |  |  | — |
Effective income tax expense and rate | $ | 153 |  |  | 17 | % | $ | 193 |  |  | 24 | % | $ | 209 |  |  | 26 | %
(a)State taxes in Missouri and Illinois made up the majority of the tax effect in this category for Ameren, Ameren Missouri, and Ameren Illinois. (b)The benefit of the credits associated with Missouri renewable energy standard compliance is refunded to customers through the RESRAM. The benefit of the credits associated with the production and investment tax credit tracker will be refunded to customers based on MoPSC approval in a regulatory rate review. (c)Reflects the amortization of a regulatory liability resulting from the revaluation of accumulated deferred income taxes subject to regulatory ratemaking, which are being refunded to customers. (d)In 2024, the IRS issued a series of private letter rulings to another taxpayer, which provided guidance on applying IRS normalization rules to the calculation of tax benefits applicable to the ratemaking treatment related to net operating loss carryforwards. The rulings concluded that, for ratemaking purposes, net operating loss carryforwards should be reflected on a separate company basis and should not be reduced by payments received for the utilization of losses by other affiliates under a tax allocation agreement. In 2025, the FERC issued an order reflecting implementation of the rules for the other taxpayer who had a similar fact pattern as Ameren Illinois and ATXI. In addition, in 2025, the ICC issued orders in Ameren Illinois’ 2024 electric distribution service revenue requirement reconciliation adjustment proceeding and in its January 2025 natural gas rate review addressing the impacts of the private letter rulings. Accordingly, in 2025, Ameren and Ameren Illinois decreased income tax expense by $86 million and $61 million, respectively, to reflect the revaluation of excess deferred income tax regulatory liabilities resulting from TCJA for FERC-regulated and ICC-regulated jurisdictions pursuant to IRS guidance and recent FERC and ICC orders. The following table presents the components of income tax expense (benefit) for the years ended December 31, 2025, 2024, and 2023:
| Ameren Missouri |  | Ameren Illinois |  | Other |  | Ameren
2025 |  |  |  |  |  |  |
Current taxes: |  |  |  |  |  |  |
Federal | $ | (140) |  |  | $ | 64 |  |  | $ | (41) |  |  | $ | (117) |
State | (2) |  |  | 19 |  |  | (17) |  |  | — |
Deferred taxes: |  |  |  |  |  |  |
Federal | 233 |  |  | 38 |  |  | (2) |  |  | 269 |
State | 38 |  |  | 63 |  |  | 1 |  |  | 102 |
Amortization of excess deferred income taxes | (75) |  |  | (31) |  |  | (1) |  |  | (107) |
Amortization of deferred investment tax credits | (11) |  |  | — |  |  | — |  |  | (11) |
Total income tax expense (benefit) | $ | 43 |  |  | $ | 153 |  |  | $ | (60) |  |  | $ | 136 |
2024 |  |  |  |  |  |  |
Current taxes: |  |  |  |  |  |  |
Federal | $ | (55) |  |  | $ | 5 |  |  | $ | 7 |  |  | $ | (43) |
State | (3) |  |  | — |  |  | 2 |  |  | (1) |
Deferred taxes: |  |  |  |  |  |  |
Federal | 45 |  |  | 144 |  |  | (12) |  |  | 177 |
State | 8 |  |  | 76 |  |  | (19) |  |  | 65 |
Amortization of excess deferred income taxes | (79) |  |  | (32) |  |  | (1) |  |  | (112) |
Amortization of deferred investment tax credits | (3) |  |  | — |  |  | — |  |  | (3) |
Total income tax expense (benefit) | $ | (87) |  |  | $ | 193 |  |  | $ | (23) |  |  | $ | 83 |
2023 |  |  |  |  |  |  |
Current taxes: |  |  |  |  |  |  |
Federal | $ | (37) |  |  | $ | 27 |  |  | $ | (37) |  |  | $ | (47) |
State | 1 |  |  | 5 |  |  | (5) |  |  | 1 |
Deferred taxes: |  |  |  |  |  |  |
Federal | 102 |  |  | 123 |  |  | 35 |  |  | 260 |
State | 9 |  |  | 71 |  |  | (10) |  |  | 70 |
Amortization of excess deferred income taxes | (80) |  |  | (17) |  |  | (1) |  |  | (98) |
Amortization of deferred investment tax credits | (3) |  |  | — |  |  | — |  |  | (3) |
Total income tax expense (benefit) | $ | (8) |  |  | $ | 209 |  |  | $ | (18) |  |  | $ | 183 |
The following table presents the accumulated deferred income tax assets and liabilities recorded as a result of temporary differences and accumulated deferred production and investment tax credits at December 31, 2025 and 2024:
| Ameren Missouri |  | Ameren Illinois |  | Other |  | Ameren
2025 |  |  |  |  |  |  |
Accumulated deferred income taxes, net liability (asset): |  |  |  |  |  |  |
Plant-related | $ | 2,652 |  |  | $ | 2,416 |  |  | $ | 244 |  |  | $ | 5,312 |
Regulatory assets and liabilities, net | (179) |  |  | (130) |  |  | (16) |  |  | (325) |
Deferred employee benefit costs | (2) |  |  | 89 |  |  | (16) |  |  | 71 |
Tax carryforwards | (190) |  |  | (45) |  |  | (108) |  |  | (343) |
Other | 161 |  |  | 21 |  |  | 21 |  |  | 203 |
Total net accumulated deferred income tax liabilities (assets) | 2,442 |  |  | 2,351 |  |  | 125 |  |  | 4,918 |
Accumulated deferred investment tax credits | 260 |  |  | 3 |  |  | — |  |  | 263 |
Accumulated deferred income taxes and investment tax credits | $ | 2,702 |  |  | $ | 2,354 |  |  | $ | 125 |  |  | $ | 5,181 |
2024 |  |  |  |  |  |  |
Accumulated deferred income taxes, net liability (asset): |  |  |  |  |  |  |
Plant-related | $ | 2,429 |  |  | $ | 2,250 |  |  | $ | 261 |  |  | $ | 4,940 |
Regulatory assets and liabilities, net | (193) |  |  | (170) |  |  | (22) |  |  | (385) |
Deferred employee benefit costs | (25) |  |  | 77 |  |  | (25) |  |  | 27 |
Tax carryforwards | (355) |  |  | (45) |  |  | (103) |  |  | (503) |
Other | 131 |  |  | 28 |  |  | 3 |  |  | 162 |
Total net accumulated deferred income tax liabilities (assets) | 1,987 |  |  | 2,140 |  |  | 114 |  |  | 4,241 |
Accumulated deferred investment tax credits | 230 |  |  | 3 |  |  | — |  |  | 233 |
Accumulated deferred income taxes and investment tax credits | $ | 2,217 |  |  | $ | 2,143 |  |  | $ | 114 |  |  | $ | 4,474 |
The following table presents the components of accumulated deferred income tax assets relating to net operating loss carryforwards and tax credit carryforwards at December 31, 2025 and 2024:
| Ameren Missouri |  | Ameren Illinois |  | Other |  | Ameren
2025 |  |  |  |  |  |  |
Net operating loss carryforwards: |  |  |  |  |  |  |
Federal(a) | $ | 53 |  |  | $ | — |  |  | $ | 24 |  |  | $ | 77 |
State(b) | 9 |  |  | 34 |  |  | 45 |  |  | 88 |
Total net operating loss carryforwards | $ | 62 |  |  | $ | 34 |  |  | $ | 69 |  |  | $ | 165 |
Tax credit carryforwards: |  |  |  |  |  |  |
Federal(c) | $ | 128 |  |  | $ | 9 |  |  | $ | 39 |  |  | $ | 176 |
State(d) | — |  |  | 2 |  |  | — |  |  | 2 |
Total tax credit carryforwards | $ | 128 |  |  | $ | 11 |  |  | $ | 39 |  |  | $ | 178 |
2024 |  |  |  |  |  |  |
Net operating loss carryforwards: |  |  |  |  |  |  |
Federal | $ | — |  |  | $ | — |  |  | $ | 30 |  |  | $ | 30 |
State | — |  |  | 34 |  |  | 29 |  |  | 63 |
Total net operating loss carryforwards | $ | — |  |  | $ | 34 |  |  | $ | 59 |  |  | $ | 93 |
Tax credit carryforwards: |  |  |  |  |  |  |
Federal | $ | 355 |  |  | $ | 9 |  |  | $ | 44 |  |  | $ | 408 |
State | — |  |  | 2 |  |  | — |  |  | 2 |
Total tax credit carryforwards | $ | 355 |  |  | $ | 11 |  |  | $ | 44 |  |  | $ | 410 |
(a)No expiration date. (b)Will expire between 2039 and 2047. (c)Will expire between 2032 and 2045. (d)Will expire between 2026 and 2030. The following table presents the total income taxes paid, net of refunds, including production and investment tax credit sale proceeds, for the years ended December 31, 2025, 2024, and 2023:
| Ameren Missouri(a) |  | Ameren Illinois(a) |  | Ameren
2025 |  | 2024 |  |  | 2023 |  | 2025 |  | 2024 |  | 2023 |  | 2025 |  | 2024 |  | 2023
Federal(b) | $ | (350) |  |  | $ | (131) |  |  |  | $ | (24) |  |  | $ | 79 |  |  | $ | (25) |  |  | $ | 76 |  |  | $ | (309) |  |  | $ | (92) |  |  | $ | (37) |
State |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Illinois | — |  |  | — |  |  |  | — |  |  | 39 |  |  | (21) |  |  | 26 |  |  | 34 |  |  | (12) |  |  | 28 |
Missouri | (9) |  |  | (5) |  |  |  | 5 |  |  | — |  |  | — |  |  | — |  |  | (37) |  |  | 12 |  |  | (15) |
Total taxes paid | $ | (359) |  |  | $ | (136) |  |  |  | $ | (19) |  |  | $ | 118 |  |  | $ | (46) |  |  | $ | 102 |  |  | $ | (312) |  |  | $ | (92) |  |  | $ | (24) |
(a)Amounts represent income tax paid, net of refunds, to Ameren (parent), pursuant to the tax allocation agreement. See Note 1 – Summary of Significant Accounting Policies – Income Taxes for additional information. (b)Includes production and investment tax credit sale proceeds for Ameren and Ameren Missouri of $314 million, $95 million, and $49 million for the years ended December 31, 2025, 2024, and 2023, respectively. Uncertain Tax Positions As of December 31, 2025 and 2024, the Ameren Companies did not record any uncertain tax positions. Ameren is a part of the IRS’s compliance assurance process program, which involves real-time review of compliance with federal income tax law. State income tax returns are generally subject to examination for a period of three years after filing. The state impact of any federal changes remains subject to examination by various states for up to one year after formal notification to the states. Ameren’s federal tax return for the 2024 tax year is open, but, at the time of this filing, the Ameren Companies do not have material income tax issues under examination, administrative appeals, or litigation.

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