Income Taxes

9 Months Ended

Sep. 30, 2019

Income Tax Disclosure [Abstract]

Income Taxes

INCOME TAXES

The following table presents a reconciliation of the federal statutory corporate income tax rate to the effective income tax rate for the three and nine months ended September 30, 2019 and 2018:

	Ameren			Ameren Missouri			Ameren Illinois
	2019	2018		2019	2018		2019	2018
Three Months
Federal statutory corporate income tax rate:	21%	21%		21%	21%		21%	21%
Increases (decreases) from:
Amortization of excess deferred taxes	(7)	(6)	(a)	(11)	(7)	(a)	(3)	(3)
Depreciation differences	—	—		—	—		—	(1)
Amortization of deferred investment tax credit	(1)	(1)		(1)	—		—	—
State tax	6	6		5	4		6	5
Stock-based compensation	1	—		—	—		—	—
TCJA	—	3	(b)	—	—		—	4	(b)
Effective income tax rate	20%	23%		14%	18%		24%	26%

	Ameren			Ameren Missouri			Ameren Illinois
	2019	2018		2019	2018		2019	2018
Nine Months
Federal statutory corporate income tax rate:	21%	21%		21%	21%		21%	21%
Increases (decreases) from:
Amortization of excess deferred taxes	(7)	(3)	(a)	(12)	(4)	(a)	(4)	(4)
Amortization of deferred investment tax credit	(1)	(1)		(1)	—		—	—
State tax	6	6		5	4		7	7
Stock-based compensation	(1)	—		—	—		—	—
TCJA	—	1	(b)	—	—		—	1	(b)
Other	—	(1)		—	—		—	—
Effective income tax rate	18%	23%		13%	21%		24%	25%

(a) Based on an order by the MoPSC in July 2018, Ameren Missouri began amortizing excess deferred taxes in August 2018.

(b) The Ameren Companies updated their respective provisional estimates recorded related to TCJA, as discussed below.

Federal Tax Reform

As of December 31, 2017, the Ameren Companies made provisional estimates for the measurement and accounting of certain effects of the TCJA in accordance with SEC guidance, which provides for a one-year period in which to complete the required analysis and update provisional estimates. During the three and nine months ended September 30, 2018, Ameren, Ameren Missouri, and Ameren Illinois updated their respective provisional estimates and recorded $13 million, $4 million, and $4 million, respectively, of income tax expense, primarily due to the application of proposed IRS regulations on depreciation transition rules. As of December 31, 2018, Ameren, Ameren Missouri, and Ameren Illinois completed their accounting for certain effects of the TCJA.