Income Taxes

3 Months Ended

Mar. 31, 2018

Income Taxes [Line Items]

Income Taxes

INCOME TAXES

Income Tax Rates - The overall income tax rates shown in the following table were computed by dividing income tax expense (benefit) by income from continuing operations before income taxes.

	Alliant Energy				IPL				WPL
Three Months Ended March 31	2018		2017		2018		2017		2018		2017
Statutory federal income tax rate	21.0	%	35.0	%	21.0	%	35.0	%	21.0	%	35.0	%
State income taxes, net of federal benefits	7.5		5.4		8.5		6.3		6.2		5.1
Effect of rate-making on property-related differences	(7.4	)	(7.5	)	(13.5	)	(17.9	)	(2.4	)	(1.7	)
Production tax credits	(5.5	)	(5.9	)	(5.4	)	(6.6	)	(6.7	)	(7.0	)
IPL’s tax benefit riders	(2.2	)	(7.8	)	(4.7	)	(19.4	)	—		—
Other items, net	(1.4	)	(4.4	)	—		(7.6	)	(0.3	)	(0.4	)
Overall income tax rate	12.0	%	14.8	%	5.9	%	(10.2	%)	17.8	%	31.0	%

Deferred Tax Assets and Liabilities - For the three months ended March 31, 2018, Alliant Energy’s, IPL’s and WPL’s deferred tax liabilities increased $33.2 million, $15.8 million and $8.5 million, respectively. These increases were primarily due to property-related differences and the utilization of federal net operating losses during the three months ended March 31, 2018. These increases were partially offset by an increase in federal credit carryforwards recorded during the three months ended March 31, 2018.

Carryforwards - At March 31, 2018, carryforwards and expiration dates were estimated as follows (in millions):

	Range of Expiration Dates	Alliant Energy		IPL		WPL
Federal net operating losses	2030-2037		$774		$497		$176
State net operating losses	2018-2038	707		13		2
Federal tax credits	2022-2038	277		123		136

IPL [Member]

Income Taxes [Line Items]

Income Taxes

INCOME TAXES

Income Tax Rates - The overall income tax rates shown in the following table were computed by dividing income tax expense (benefit) by income from continuing operations before income taxes.

	Alliant Energy				IPL				WPL
Three Months Ended March 31	2018		2017		2018		2017		2018		2017
Statutory federal income tax rate	21.0	%	35.0	%	21.0	%	35.0	%	21.0	%	35.0	%
State income taxes, net of federal benefits	7.5		5.4		8.5		6.3		6.2		5.1
Effect of rate-making on property-related differences	(7.4	)	(7.5	)	(13.5	)	(17.9	)	(2.4	)	(1.7	)
Production tax credits	(5.5	)	(5.9	)	(5.4	)	(6.6	)	(6.7	)	(7.0	)
IPL’s tax benefit riders	(2.2	)	(7.8	)	(4.7	)	(19.4	)	—		—
Other items, net	(1.4	)	(4.4	)	—		(7.6	)	(0.3	)	(0.4	)
Overall income tax rate	12.0	%	14.8	%	5.9	%	(10.2	%)	17.8	%	31.0	%

Deferred Tax Assets and Liabilities - For the three months ended March 31, 2018, Alliant Energy’s, IPL’s and WPL’s deferred tax liabilities increased $33.2 million, $15.8 million and $8.5 million, respectively. These increases were primarily due to property-related differences and the utilization of federal net operating losses during the three months ended March 31, 2018. These increases were partially offset by an increase in federal credit carryforwards recorded during the three months ended March 31, 2018.

Carryforwards - At March 31, 2018, carryforwards and expiration dates were estimated as follows (in millions):

	Range of Expiration Dates	Alliant Energy		IPL		WPL
Federal net operating losses	2030-2037		$774		$497		$176
State net operating losses	2018-2038	707		13		2
Federal tax credits	2022-2038	277		123		136

WPL [Member]

Income Taxes [Line Items]

Income Taxes

INCOME TAXES

Income Tax Rates - The overall income tax rates shown in the following table were computed by dividing income tax expense (benefit) by income from continuing operations before income taxes.

	Alliant Energy				IPL				WPL
Three Months Ended March 31	2018		2017		2018		2017		2018		2017
Statutory federal income tax rate	21.0	%	35.0	%	21.0	%	35.0	%	21.0	%	35.0	%
State income taxes, net of federal benefits	7.5		5.4		8.5		6.3		6.2		5.1
Effect of rate-making on property-related differences	(7.4	)	(7.5	)	(13.5	)	(17.9	)	(2.4	)	(1.7	)
Production tax credits	(5.5	)	(5.9	)	(5.4	)	(6.6	)	(6.7	)	(7.0	)
IPL’s tax benefit riders	(2.2	)	(7.8	)	(4.7	)	(19.4	)	—		—
Other items, net	(1.4	)	(4.4	)	—		(7.6	)	(0.3	)	(0.4	)
Overall income tax rate	12.0	%	14.8	%	5.9	%	(10.2	%)	17.8	%	31.0	%

Deferred Tax Assets and Liabilities - For the three months ended March 31, 2018, Alliant Energy’s, IPL’s and WPL’s deferred tax liabilities increased $33.2 million, $15.8 million and $8.5 million, respectively. These increases were primarily due to property-related differences and the utilization of federal net operating losses during the three months ended March 31, 2018. These increases were partially offset by an increase in federal credit carryforwards recorded during the three months ended March 31, 2018.

Carryforwards - At March 31, 2018, carryforwards and expiration dates were estimated as follows (in millions):

	Range of Expiration Dates	Alliant Energy		IPL		WPL
Federal net operating losses	2030-2037		$774		$497		$176
State net operating losses	2018-2038	707		13		2
Federal tax credits	2022-2038	277		123		136