Income Taxes

9 Months Ended

Sep. 30, 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 September 30	2017		2016		2017		2016		2017		2016
Statutory federal income tax rate	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%
Effect of rate-making on property-related differences	(10.1	)	(11.9	)	(22.6	)	(16.5	)	(1.9	)	(0.7	)
IPL’s tax benefit riders	(8.3	)	(13.1	)	(20.9	)	(20.1	)	—		—
Production tax credits	(6.2	)	(9.0	)	(7.0	)	(6.0	)	(7.0	)	(5.7	)
Other items, net	2.8		4.4		2.3		5.4		5.5		4.0
Overall income tax rate	13.2	%	5.4	%	(13.2	%)	(2.2	%)	31.6	%	32.6	%

	Alliant Energy				IPL				WPL
Nine Months Ended September 30	2017		2016		2017		2016		2017		2016
Statutory federal income tax rate	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%
Effect of rate-making on property-related differences	(9.1	)	(8.2	)	(20.6	)	(14.8	)	(1.8	)	(0.8	)
IPL’s tax benefit riders	(8.1	)	(10.2	)	(20.1	)	(19.6	)	—		—
Production tax credits	(6.0	)	(7.2	)	(6.8	)	(6.1	)	(7.0	)	(6.1	)
Other items, net	3.1		3.5		2.7		4.2		4.9		4.4
Overall income tax rate	14.9	%	12.9	%	(9.8	%)	(1.3	%)	31.1	%	32.5	%

Deferred Tax Assets and Liabilities - For the nine months ended September 30, 2017, Alliant Energy’s, IPL’s and WPL’s deferred tax liabilities increased $204.5 million, $131.7 million and $63.6 million, respectively. These increases were primarily due to property-related differences recorded during the nine months ended September 30, 2017. Alliant Energy’s and IPL’s increases were partially offset by the generation of federal net operating losses recorded during the nine months ended September 30, 2017, which are primarily due to accelerated tax depreciation associated with Marshalltown.

Carryforwards - At September 30, 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		$815		$500		$208
State net operating losses	2018-2037	701		14		2
Federal tax credits	2022-2037	297		110		125

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 September 30	2017		2016		2017		2016		2017		2016
Statutory federal income tax rate	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%
Effect of rate-making on property-related differences	(10.1	)	(11.9	)	(22.6	)	(16.5	)	(1.9	)	(0.7	)
IPL’s tax benefit riders	(8.3	)	(13.1	)	(20.9	)	(20.1	)	—		—
Production tax credits	(6.2	)	(9.0	)	(7.0	)	(6.0	)	(7.0	)	(5.7	)
Other items, net	2.8		4.4		2.3		5.4		5.5		4.0
Overall income tax rate	13.2	%	5.4	%	(13.2	%)	(2.2	%)	31.6	%	32.6	%

	Alliant Energy				IPL				WPL
Nine Months Ended September 30	2017		2016		2017		2016		2017		2016
Statutory federal income tax rate	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%
Effect of rate-making on property-related differences	(9.1	)	(8.2	)	(20.6	)	(14.8	)	(1.8	)	(0.8	)
IPL’s tax benefit riders	(8.1	)	(10.2	)	(20.1	)	(19.6	)	—		—
Production tax credits	(6.0	)	(7.2	)	(6.8	)	(6.1	)	(7.0	)	(6.1	)
Other items, net	3.1		3.5		2.7		4.2		4.9		4.4
Overall income tax rate	14.9	%	12.9	%	(9.8	%)	(1.3	%)	31.1	%	32.5	%

Deferred Tax Assets and Liabilities - For the nine months ended September 30, 2017, Alliant Energy’s, IPL’s and WPL’s deferred tax liabilities increased $204.5 million, $131.7 million and $63.6 million, respectively. These increases were primarily due to property-related differences recorded during the nine months ended September 30, 2017. Alliant Energy’s and IPL’s increases were partially offset by the generation of federal net operating losses recorded during the nine months ended September 30, 2017, which are primarily due to accelerated tax depreciation associated with Marshalltown.

Carryforwards - At September 30, 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		$815		$500		$208
State net operating losses	2018-2037	701		14		2
Federal tax credits	2022-2037	297		110		125

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 September 30	2017		2016		2017		2016		2017		2016
Statutory federal income tax rate	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%
Effect of rate-making on property-related differences	(10.1	)	(11.9	)	(22.6	)	(16.5	)	(1.9	)	(0.7	)
IPL’s tax benefit riders	(8.3	)	(13.1	)	(20.9	)	(20.1	)	—		—
Production tax credits	(6.2	)	(9.0	)	(7.0	)	(6.0	)	(7.0	)	(5.7	)
Other items, net	2.8		4.4		2.3		5.4		5.5		4.0
Overall income tax rate	13.2	%	5.4	%	(13.2	%)	(2.2	%)	31.6	%	32.6	%

	Alliant Energy				IPL				WPL
Nine Months Ended September 30	2017		2016		2017		2016		2017		2016
Statutory federal income tax rate	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%
Effect of rate-making on property-related differences	(9.1	)	(8.2	)	(20.6	)	(14.8	)	(1.8	)	(0.8	)
IPL’s tax benefit riders	(8.1	)	(10.2	)	(20.1	)	(19.6	)	—		—
Production tax credits	(6.0	)	(7.2	)	(6.8	)	(6.1	)	(7.0	)	(6.1	)
Other items, net	3.1		3.5		2.7		4.2		4.9		4.4
Overall income tax rate	14.9	%	12.9	%	(9.8	%)	(1.3	%)	31.1	%	32.5	%

Deferred Tax Assets and Liabilities - For the nine months ended September 30, 2017, Alliant Energy’s, IPL’s and WPL’s deferred tax liabilities increased $204.5 million, $131.7 million and $63.6 million, respectively. These increases were primarily due to property-related differences recorded during the nine months ended September 30, 2017. Alliant Energy’s and IPL’s increases were partially offset by the generation of federal net operating losses recorded during the nine months ended September 30, 2017, which are primarily due to accelerated tax depreciation associated with Marshalltown.

Carryforwards - At September 30, 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		$815		$500		$208
State net operating losses	2018-2037	701		14		2
Federal tax credits	2022-2037	297		110		125