Income Taxes

3 Months Ended

Mar. 31, 2017

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	2017		2016		2017		2016		2017		2016
Statutory federal income tax rate	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%
IPL’s tax benefit riders	(7.8	)	(8.7	)	(19.4	)	(20.7	)	—		—
Effect of rate-making on property-related differences	(7.5	)	(6.8	)	(17.9	)	(15.2	)	(1.7	)	(0.8	)
Production tax credits	(5.9	)	(6.3	)	(6.6	)	(6.7	)	(7.0	)	(6.5	)
Other items, net	1.0		4.5		(1.3	)	5.9		4.7		4.8
Overall income tax rate	14.8	%	17.7	%	(10.2	%)	(1.7	%)	31.0	%	32.5	%

Deferred Tax Assets and Liabilities - For the three months ended March 31, 2017, Alliant Energy’s, IPL’s and WPL’s deferred tax liabilities increased $55.7 million, $41.4 million and $13.1 million, respectively. These increases were primarily due to property-related differences recorded during the three months ended March 31, 2017. Alliant Energy’s and IPL’s increases were partially offset by the generation of federal net operating losses recorded during the three months ended March 31, 2017, which are primarily due to the accelerated tax depreciation associated with Marshalltown.

Carryforwards - At March 31, 2017, carryforwards and expiration dates were estimated as follows (in millions):

	Range of Expiration Dates	Alliant Energy		IPL		WPL
Federal net operating losses	2030-2037		$633		$315		$217
State net operating losses	2018-2037	696		13		2
Federal tax credits	2022-2037	284		104		118

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	2017		2016		2017		2016		2017		2016
Statutory federal income tax rate	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%
IPL’s tax benefit riders	(7.8	)	(8.7	)	(19.4	)	(20.7	)	—		—
Effect of rate-making on property-related differences	(7.5	)	(6.8	)	(17.9	)	(15.2	)	(1.7	)	(0.8	)
Production tax credits	(5.9	)	(6.3	)	(6.6	)	(6.7	)	(7.0	)	(6.5	)
Other items, net	1.0		4.5		(1.3	)	5.9		4.7		4.8
Overall income tax rate	14.8	%	17.7	%	(10.2	%)	(1.7	%)	31.0	%	32.5	%

Deferred Tax Assets and Liabilities - For the three months ended March 31, 2017, Alliant Energy’s, IPL’s and WPL’s deferred tax liabilities increased $55.7 million, $41.4 million and $13.1 million, respectively. These increases were primarily due to property-related differences recorded during the three months ended March 31, 2017. Alliant Energy’s and IPL’s increases were partially offset by the generation of federal net operating losses recorded during the three months ended March 31, 2017, which are primarily due to the accelerated tax depreciation associated with Marshalltown.

Carryforwards - At March 31, 2017, carryforwards and expiration dates were estimated as follows (in millions):

	Range of Expiration Dates	Alliant Energy		IPL		WPL
Federal net operating losses	2030-2037		$633		$315		$217
State net operating losses	2018-2037	696		13		2
Federal tax credits	2022-2037	284		104		118

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	2017		2016		2017		2016		2017		2016
Statutory federal income tax rate	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%
IPL’s tax benefit riders	(7.8	)	(8.7	)	(19.4	)	(20.7	)	—		—
Effect of rate-making on property-related differences	(7.5	)	(6.8	)	(17.9	)	(15.2	)	(1.7	)	(0.8	)
Production tax credits	(5.9	)	(6.3	)	(6.6	)	(6.7	)	(7.0	)	(6.5	)
Other items, net	1.0		4.5		(1.3	)	5.9		4.7		4.8
Overall income tax rate	14.8	%	17.7	%	(10.2	%)	(1.7	%)	31.0	%	32.5	%

Deferred Tax Assets and Liabilities - For the three months ended March 31, 2017, Alliant Energy’s, IPL’s and WPL’s deferred tax liabilities increased $55.7 million, $41.4 million and $13.1 million, respectively. These increases were primarily due to property-related differences recorded during the three months ended March 31, 2017. Alliant Energy’s and IPL’s increases were partially offset by the generation of federal net operating losses recorded during the three months ended March 31, 2017, which are primarily due to the accelerated tax depreciation associated with Marshalltown.

Carryforwards - At March 31, 2017, carryforwards and expiration dates were estimated as follows (in millions):

	Range of Expiration Dates	Alliant Energy		IPL		WPL
Federal net operating losses	2030-2037		$633		$315		$217
State net operating losses	2018-2037	696		13		2
Federal tax credits	2022-2037	284		104		118