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Retirement Benefits (Tables)
 12 Months Ended
Dec. 31, 2025
Summary Of Benefit Liability Recorded
The following table presents the net benefit liability/(asset) recorded on the balance sheets as of December 31, 2025 and 2024:
20252024
Ameren(a)
$(954)$(734)
Ameren Missouri(a)
(261)(201)
Ameren Illinois(a)
(563)(438)
(a)Liabilities associated with pension and other postretirement benefits are recorded in “Other current liabilities” and “Other deferred credits and liabilities” on Ameren’s, Ameren Missouri’s, and Ameren Illinois’ balance sheets.
Funded Status Of Benefit Plans and Amounts Included In Regulatory Assets and AOCI The following table presents the funded status of Ameren’s pension and postretirement benefit plans as of December 31, 2025 and 2024. It also provides the amounts included in regulatory assets or liabilities and accumulated OCI at December 31, 2025 and 2024, that have not been recognized in net periodic benefit costs.
20252024
Pension
Benefits		Postretirement
Benefits		Pension
Benefits		Postretirement
Benefits
Accumulated benefit obligation at end of year$3,773 $(a)$3,962 $(a)
Change in benefit obligation:
Net benefit obligation at beginning of year$4,134 $807 $4,258 $856 
Service cost82 10 88 12 
Interest cost234 45 222 44 
Participant contributions— 7 — 7 
Actuarial (gain) loss28 
(b)
5 (143)(51)
Contract transfer(c)
(240)— — — 
Benefits paid(299)(68)(291)(61)
Net benefit obligation at end of year3,939 806 4,134 807 
Change in plan assets:
Fair value of plan assets at beginning of year4,182 1,493 4,272 1,393 
Actual return on plan assets456 162 193 150 
Employer contributions3 3 8 4 
Participant contributions— 7 — 7 
Contract transfer(c)
(240)— — — 
Benefits paid(299)(68)(291)(61)
Fair value of plan assets at end of year4,102 1,597 4,182 1,493 
Funded status – surplus(163)(791)(48)(686)
Accrued benefit asset at December 31$(163)$(791)$(48)$(686)
Amounts recognized in the balance sheet consist of:
Noncurrent asset$(186)$(791)$(71)$(686)
Current liability(d)
2 — 2 — 
Noncurrent liability(e)
21 — 21 — 
Net asset recognized$(163)$(791)$(48)$(686)
Amounts recognized in regulatory assets or liabilities consist of:
Net actuarial (gain) loss$(45)$(404)$42 $(379)
Prior service credit— (18)— (21)
Amounts recognized in accumulated OCI (pretax) consist of:
Net actuarial (gain) loss22 (7)26 (7)
Total$(23)$(429)$68 $(407)
(a)Not applicable.
(b)Includes a $15 million gain from the contract transfer of defined benefit pension obligations and related plan assets to a third-party insurance company in December 2025 as described above.
(c)Represents the contract transfer of defined benefit pension obligations and related plan assets to a third-party insurance company in December 2025 as described above.
(d)Included in “Other current liabilities” on Ameren’s consolidated balance sheet.
(e)Included in “Other deferred credits and liabilities” on Ameren’s consolidated balance sheet.
Assumptions Used To Determine Benefit Obligations
The following table presents the assumptions used to determine our benefit obligations at December 31, 2025 and 2024:
Pension BenefitsPostretirement Benefits
2025202420252024
Discount rate at measurement date5.75 %5.70 %5.70 %5.70 %
Increase in future compensation4.00 4.00 4.00 4.00 
Cash balance pension plan interest crediting rate5.50 5.50 (a)(a)
Medical cost trend rate (initial)(b)
(a)(a)(c)(c)
Medical cost trend rate (ultimate)(b)
(a)(a)5.00 5.00 
(a)Not applicable.
(b)Initial and ultimate medical cost trend rate for certain Medicare-eligible participants was 2.50% at December 31, 2025 and 2024.
(c)Initial medical cost trend rates of 7.50% and 7.00% for both pre-Medicare plan participants and post-Medicare plan participants at December 31, 2025 and 2024, respectively, trend down to the ultimate rate by 2036 and 2033, respectively, with a 3.00% upward adjustment to the post-Medicare trend rate in 2024.
Schedule Of Cash Contributions Made To Benefit Plans
The following table presents the cash contributions made to our defined benefit retirement plans and to our postretirement plan during 2025, 2024, and 2023:
Pension BenefitsPostretirement Benefits
202520242023202520242023
Ameren Missouri$1 $1 $1 $1 $2 $2 
Ameren Illinois1 1 2 1 1 1 
Ameren Services1 6 1 1 1 — 
Ameren$3 $8 $4 $3 $4 $3 
Target Allocation Of The Plans' Asset Categories
The following table presents our target allocations and our pension and postretirement plans’ asset categories as of December 31, 2025 and 2024:
Asset
Category
Target Allocation
2025
Percentage of Plan Assets at December 31,
20252024
Pension Plan:
Cash and cash equivalents
0% – 5%
3 %3 %
Equity securities:
U.S. large-capitalization
10% – 20%
15 %16 %
U.S. small- and mid-capitalization
3% – 13%
9 %9 %
Global
10% – 20%
16 %15 %
International
4% – 14%
7 %9 %
Total equity
42% – 52%
47 %49 %
Debt securities
32% – 42%
34 %
(a)
35 %
(a)
Diversified credit
6% – 16%
10 %8 %
Real estate
0% – 10%
6 %5 %
Private equity
0% – 5%
— %(b)
Total 100 %100 %
Postretirement Plans:
Cash and cash equivalents
0% – 7%
2 %2 %
Equity securities:
U.S. large-capitalization
23% – 33%
33 %33 %
U.S. small- and mid-capitalization
3% – 13%
7 %8 %
Global
9% – 19%
13 %13 %
International
5% – 15%
8 %8 %
Total equity
55% – 65%
61 %62 %
Debt securities
33% – 43%
37 %36 %
Total 100 %100 %
(a)Includes interest rate futures derivative instruments.
(b)Less than 1% of plan assets.
Components Of Net Periodic Benefit Cost
The following table presents the components of the net periodic benefit cost (income) of Ameren’s pension and postretirement benefit plans during 2025, 2024, and 2023:
Pension BenefitsPostretirement Benefits
202520242023202520242023
Service cost(a)
$82 $88 $79 $10 $12 $12 
Non-service cost components:
Interest cost234 222 221 45 44 45 
Expected return on plan assets(b)
(303)(327)(333)(94)(93)(91)
Amortization of(b):
Prior service cost (credit)— — — (4)(4)(4)
Actuarial (gain)(34)(67)(115)(38)(38)(45)
Total non-service cost components(c)
$(103)$(172)$(227)$(91)$(91)$(95)
Net periodic benefit cost (income)(d)
$(21)$(84)$(148)$(81)$(79)$(83)
(a)Service cost, net of capitalization, is reflected in “Operating Expenses - Other operations and maintenance” on Ameren’s statement of income.
(b)Prior service cost (credit) is amortized on a straight-line basis over the average future service of active participants benefiting under the plan amendment. Net actuarial gains or losses subject to amortization are amortized on a straight-line basis over 10 years. Expected return on plan assets is based on a market-related value of assets that recognizes asset (gains) losses over 4 years.
(c)Non-service cost components are reflected in “Other Income, Net” on Ameren’s consolidated statement of income. See Note 6 – Other Income, Net for additional information.
(d)Does not include the impact of the tracker for the difference between the level of pension and postretirement benefit costs (income) incurred by Ameren Missouri under GAAP and the level of such costs included in rates.
Summary Of Benefit Plan Costs Incurred
The Ameren Companies are responsible for their share of the pension and postretirement benefit costs (income). The following table presents the pension and postretirement benefit costs (income) incurred for the years ended December 31, 2025, 2024, and 2023:
Pension CostsPostretirement Costs
202520242023202520242023
Ameren Missouri(a)
$(14)$(44)$(76)$(28)$(27)$(30)
Ameren Illinois(4)(34)(62)(53)(52)(54)
Other(3)(6)(10)— — 1 
Ameren$(21)$(84)$(148)$(81)$(79)$(83)
(a)Does not include the impact of the tracker for the difference between the level of pension and postretirement benefit costs (income) incurred by Ameren Missouri under GAAP and the level of such costs included in customer rates.
Schedule Of Expected Payments From Qualified Trust And Company Funds
The expected pension and postretirement benefit payments from qualified trust and company funds, which reflect expected future service, as of December 31, 2025, are as follows:
Pension BenefitsPostretirement Benefits
Paid from
Qualified
Trust Funds		Paid from
Company
Funds		Paid from
Qualified
Trust Funds		Paid from
Company
Funds
2026$262 $2 $59 $3 
2027267 2 59 3 
2028271 2 59 3 
2029275 2 58 3 
2030279 2 58 3 
2031 – 20351,424 14 288 13 
Assumptions Used To Determine Net Periodic Benefit Cost
The following table presents the assumptions used to determine net periodic benefit cost for our pension and postretirement benefit plans for the years ended December 31, 2025, 2024, and 2023:
Pension BenefitsPostretirement Benefits
202520242023202520242023
Discount rate at measurement date5.70 %5.25 %5.55 %5.70 %5.25 %5.55 %
Expected return on plan assets6.75 6.75 6.75 6.75 6.75 6.75 
Increase in future compensation(a)
4.00 3.50 3.50 4.00 3.50 3.50 
Cash balance pension plan interest crediting rate(b)
5.50 5.50 5.00 (c)(c)(c)
Medical cost trend rate (initial)(d)
(c)(c)(c)(e)(f)(g)
Medical cost trend rate (ultimate)(d)
(c)(c)(c)5.00 5.00 5.00 
(a)Increase in future compensation is 4.00% for the year ended December 31, 2025, 4.00% for 2024 and 3.50% thereafter for the year ended December 31, 2024, and 4.50% for 2023, 4.00% for 2024, and 3.50% thereafter for the year ended December 31, 2023.
(b)Cash balance pension plan interest crediting rate is 5.20% for 2025 and 5.50% thereafter for the year ended December 31, 2025, was 6.42% for 2024, and 5.50% thereafter for the year ended December 31, 2024, and 5.50% for 2023 and 2024, and 5.00% thereafter for the year ended December 31, 2023.
(c)Not applicable.
(d)Initial and ultimate medical cost trend rate for certain Medicare-eligible participants is 2.50% for the years ended December 31, 2025, 2024, and 2023.
(e)Initial medical cost trend rates of 7.00% for pre-Medicare plan participants and 7.00% for post-Medicare plan participants trend down to the ultimate rate by 2033 with a 3.00% upward adjustment to the post-Medicare trend rate in 2025.
(f)Initial medical cost trend rates of 6.93% for pre-Medicare plan participants and 6.50% for post-Medicare plan participants trend down to the ultimate rate by 2030, with a 3.00% upward adjustment to the post-Medicare trend rate in 2025.
(g)Initial medical cost trend rates of 7.25% for pre-Medicare plan participants and 6.75% for post-Medicare plan participants trend down to the ultimate rate by 2030, with a 3.00% upward adjustment to the post-Medicare trend rate in 2025.
Schedule Of Matching Contributions The following table presents the portion of the matching contribution to the Ameren 401(k) plan attributable to each of the Ameren Companies for the years ended December 31, 2025, 2024, and 2023:
202520242023
Ameren Missouri$26 $26 $27 
Ameren Illinois22 22 21 
Other1 1 1 
Ameren$49 $49 $49 
Pension Benefits  
Target Allocation Of The Plans' Asset Categories
The following table sets forth, by level within the fair value hierarchy discussed in Note 8 – Fair Value Measurements, the pension plans’ assets measured at fair value and NAV as of December 31, 2025 and 2024:
December 31, 2025December 31, 2024
Level 1Level 2NAVTotalLevel 1Level 2NAVTotal
Cash and cash equivalents$— $— $96 $96 $— $— $75 $75 
Equity securities:
U.S. large-capitalization— — 648 648 — — 689 689 
U.S. small- and mid-capitalization382 — — 382 375 — — 375 
International120 — 203 323 182 — 226 408 
Global— — 671 671 — — 680 680 
Debt securities:
Corporate bonds— 418 — 418 — 463 — 463 
Municipal bonds— 36 — 36 — 36 — 36 
U.S. Treasury and agency securities— 1,016 — 1,016 — 1,032 — 1,032 
Diversified credit— — 456 456 — — 344 344 
Other(10)7 — (3)(17)11 — (6)
Real estate— — 243 243 — — 233 233 
Total$492 $1,477 $2,317 $4,286 $540 $1,542 $2,247 $4,329 
Less: Medical benefit assets(a)
(222)(200)
Plus: Net receivables (payables)(b)
38 53 
Fair value of pension plans’ assets$4,102 $4,182 
(a)Medical benefit (health and welfare) component for accounts maintained in accordance with Section 401(h) of the Internal Revenue Code to fund a portion of the postretirement obligation.
(b)Net of receivables related to pending securities sales and payables related to pending securities purchases.
Postretirement Benefits  
Target Allocation Of The Plans' Asset Categories
The following table sets forth, by level within the fair value hierarchy discussed in Note 8 – Fair Value Measurements, the postretirement benefit plans’ assets measured at fair value and NAV as of December 31, 2025 and 2024:
December 31, 2025December 31, 2024
Level 1Level 2NAVTotalLevel 1Level 2NAVTotal
Cash and cash equivalents$18 $— $— $18 $25 $— $— $25 
Equity securities:
U.S. large-capitalization353 — 106 459 332 — 91 423 
U.S. small- and mid-capitalization100 — — 100 106 — — 106 
International56 — 59 115 54 — 52 106 
Global— — 178 178 — — 165 165 
Debt securities:
Municipal bonds— 187 — 187 — 173 — 173 
Other— — 315 315 — — 293 293 
Total$527 $187 $658 $1,372 $517 $173 $601 $1,291 
Plus: Medical benefit assets(a)
222 200 
Plus: Net receivables(b)
  3 2 
Fair value of postretirement benefit plans’ assets  $1,597 $1,493 
(a)Medical benefit (health and welfare) component for accounts maintained in accordance with Section 401(h) of the Internal Revenue Code to fund a portion of the postretirement obligation. These 401(h) assets are included in the pension plan assets shown above.
(b)Net of receivables related to pending securities sales and payables related to pending securities purchases.