Income Taxes Income Taxes (Tables)

3 Months Ended

Mar. 31, 2023

Income Tax Disclosure [Abstract]

Schedule of Effective Income Tax Rate Reconciliation

The following table presents a reconciliation of the federal statutory corporate income tax rate to the effective income tax rate for the three months ended March 31, 2023 and 2022:

	Ameren				Ameren Missouri				Ameren Illinois
	2023		2022		2023		2022		2023		2022
Three Months
Federal statutory corporate income tax rate	21	%	21	%	21	%	21	%	21	%	21	%
Increases (decreases) from:
Amortization of deferred investment tax credit	—		—		—		(1)		—		—
Amortization of excess deferred taxes(a)	(8)		(8)		(16)		(16)		(2)		(2)
Renewable and other tax credits(b)	(5)		(5)		(10)		(11)		—		—
State tax	6		5		4		3		7		7
Stock-based compensation	(1)		(1)		—		—		—		—
Other permanent items	(1)		—		(3)		—		(1)		—
Effective income tax rate	12	%	12	%	(4)	%	(4)	%	25	%	26	%

(a)Reflects the amortization of amounts resulting from the revaluation of deferred income taxes subject to regulatory ratemaking, which are being refunded to customers. Deferred income taxes are revalued when federal or state income tax rates change, and the offset to the revaluation of deferred income taxes subject to regulatory ratemaking is recorded to a regulatory asset or liability.

(b)The benefit of the credits associated with Missouri renewable energy standard compliance is refunded to customers through the RESRAM.