Income Taxes

9 Months Ended

Sep. 30, 2015

Income Taxes [Line Items]

Income Taxes

INCOME TAXES

Income Tax Rates - The provision for income taxes for earnings from continuing operations is based on an estimated annual effective income tax rate that excludes the impact of significant unusual or infrequently occurring items, discontinued operations or extraordinary items. 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	2015		2014		2015		2014		2015		2014
Statutory federal income tax rate	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%
IPL’s tax benefit riders	(11.0	)	(13.0	)	(30.0	)	(39.2	)	—		—
Effect of rate-making on property-related differences	(7.1	)	(8.6	)	(18.7	)	(22.4	)	(0.7	)	(0.8	)
Production tax credits	(6.7	)	(6.8	)	(8.7	)	(9.3	)	(6.0	)	(6.2	)
Other items, net	3.0		0.7		2.9		2.2		4.5		—
Overall income tax rate	13.2	%	7.3	%	(19.5	%)	(33.7	%)	32.8	%	28.0	%

	Alliant Energy				IPL				WPL
Nine Months Ended September 30	2015		2014		2015		2014		2015		2014
Statutory federal income tax rate	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%
IPL’s tax benefit riders	(10.6	)	(12.4	)	(28.2	)	(36.5	)	—		—
Effect of rate-making on property-related differences	(7.1	)	(6.7	)	(17.9	)	(18.4	)	(0.6	)	(0.7	)
Production tax credits	(6.6	)	(6.6	)	(8.2	)	(8.8	)	(6.2	)	(6.2	)
Other items, net	3.7		2.9		3.5		3.2		4.5		3.0
Overall income tax rate	14.4	%	12.2	%	(15.8	%)	(25.5	%)	32.7	%	31.1	%

IPL’s tax benefit riders - Alliant Energy’s and IPL’s effective income tax rates include the impact of reducing income tax expense with offsetting reductions to regulatory liabilities as a result of implementing IPL’s tax benefit riders. Refer to Note 2 for additional details of the tax benefit riders.

Deferred Tax Assets and Liabilities - For the nine months ended September 30, 2015, Alliant Energy’s, IPL’s and WPL’s non-current deferred tax liabilities increased $141.0 million, $78.5 million and $60.1 million, respectively. These increases in non-current deferred tax liabilities were primarily due to utilization of federal net operating loss carryforwards, and property-related differences recorded during the nine months ended September 30, 2015, including an increase in qualifying repairs expenditures.

Carryforwards - At September 30, 2015, tax carryforwards and associated deferred tax assets and expiration dates were estimated as follows (dollars in millions):

		Alliant Energy				IPL				WPL
	Earliest Expiration Date	Tax Carryforwards		Deferred Tax Assets		Tax Carryforwards		Deferred Tax Assets		Tax Carryforwards		Deferred Tax Assets
Federal net operating losses	2030		$527		$180		$231		$79		$218		$75
State net operating losses	2018	731		37		183		9		126		6
Federal tax credits	2022	227		224		80		78		89		87
					$441				$166				$168

IPL [Member]

Income Taxes [Line Items]

Income Taxes

INCOME TAXES

Income Tax Rates - The provision for income taxes for earnings from continuing operations is based on an estimated annual effective income tax rate that excludes the impact of significant unusual or infrequently occurring items, discontinued operations or extraordinary items. 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	2015		2014		2015		2014		2015		2014
Statutory federal income tax rate	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%
IPL’s tax benefit riders	(11.0	)	(13.0	)	(30.0	)	(39.2	)	—		—
Effect of rate-making on property-related differences	(7.1	)	(8.6	)	(18.7	)	(22.4	)	(0.7	)	(0.8	)
Production tax credits	(6.7	)	(6.8	)	(8.7	)	(9.3	)	(6.0	)	(6.2	)
Other items, net	3.0		0.7		2.9		2.2		4.5		—
Overall income tax rate	13.2	%	7.3	%	(19.5	%)	(33.7	%)	32.8	%	28.0	%

	Alliant Energy				IPL				WPL
Nine Months Ended September 30	2015		2014		2015		2014		2015		2014
Statutory federal income tax rate	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%
IPL’s tax benefit riders	(10.6	)	(12.4	)	(28.2	)	(36.5	)	—		—
Effect of rate-making on property-related differences	(7.1	)	(6.7	)	(17.9	)	(18.4	)	(0.6	)	(0.7	)
Production tax credits	(6.6	)	(6.6	)	(8.2	)	(8.8	)	(6.2	)	(6.2	)
Other items, net	3.7		2.9		3.5		3.2		4.5		3.0
Overall income tax rate	14.4	%	12.2	%	(15.8	%)	(25.5	%)	32.7	%	31.1	%

IPL’s tax benefit riders - Alliant Energy’s and IPL’s effective income tax rates include the impact of reducing income tax expense with offsetting reductions to regulatory liabilities as a result of implementing IPL’s tax benefit riders. Refer to Note 2 for additional details of the tax benefit riders.

Deferred Tax Assets and Liabilities - For the nine months ended September 30, 2015, Alliant Energy’s, IPL’s and WPL’s non-current deferred tax liabilities increased $141.0 million, $78.5 million and $60.1 million, respectively. These increases in non-current deferred tax liabilities were primarily due to utilization of federal net operating loss carryforwards, and property-related differences recorded during the nine months ended September 30, 2015, including an increase in qualifying repairs expenditures.

Carryforwards - At September 30, 2015, tax carryforwards and associated deferred tax assets and expiration dates were estimated as follows (dollars in millions):

		Alliant Energy				IPL				WPL
	Earliest Expiration Date	Tax Carryforwards		Deferred Tax Assets		Tax Carryforwards		Deferred Tax Assets		Tax Carryforwards		Deferred Tax Assets
Federal net operating losses	2030		$527		$180		$231		$79		$218		$75
State net operating losses	2018	731		37		183		9		126		6
Federal tax credits	2022	227		224		80		78		89		87
					$441				$166				$168

WPL [Member]

Income Taxes [Line Items]

Income Taxes

INCOME TAXES

Income Tax Rates - The provision for income taxes for earnings from continuing operations is based on an estimated annual effective income tax rate that excludes the impact of significant unusual or infrequently occurring items, discontinued operations or extraordinary items. 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	2015		2014		2015		2014		2015		2014
Statutory federal income tax rate	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%
IPL’s tax benefit riders	(11.0	)	(13.0	)	(30.0	)	(39.2	)	—		—
Effect of rate-making on property-related differences	(7.1	)	(8.6	)	(18.7	)	(22.4	)	(0.7	)	(0.8	)
Production tax credits	(6.7	)	(6.8	)	(8.7	)	(9.3	)	(6.0	)	(6.2	)
Other items, net	3.0		0.7		2.9		2.2		4.5		—
Overall income tax rate	13.2	%	7.3	%	(19.5	%)	(33.7	%)	32.8	%	28.0	%

	Alliant Energy				IPL				WPL
Nine Months Ended September 30	2015		2014		2015		2014		2015		2014
Statutory federal income tax rate	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%
IPL’s tax benefit riders	(10.6	)	(12.4	)	(28.2	)	(36.5	)	—		—
Effect of rate-making on property-related differences	(7.1	)	(6.7	)	(17.9	)	(18.4	)	(0.6	)	(0.7	)
Production tax credits	(6.6	)	(6.6	)	(8.2	)	(8.8	)	(6.2	)	(6.2	)
Other items, net	3.7		2.9		3.5		3.2		4.5		3.0
Overall income tax rate	14.4	%	12.2	%	(15.8	%)	(25.5	%)	32.7	%	31.1	%

IPL’s tax benefit riders - Alliant Energy’s and IPL’s effective income tax rates include the impact of reducing income tax expense with offsetting reductions to regulatory liabilities as a result of implementing IPL’s tax benefit riders. Refer to Note 2 for additional details of the tax benefit riders.

Deferred Tax Assets and Liabilities - For the nine months ended September 30, 2015, Alliant Energy’s, IPL’s and WPL’s non-current deferred tax liabilities increased $141.0 million, $78.5 million and $60.1 million, respectively. These increases in non-current deferred tax liabilities were primarily due to utilization of federal net operating loss carryforwards, and property-related differences recorded during the nine months ended September 30, 2015, including an increase in qualifying repairs expenditures.

Carryforwards - At September 30, 2015, tax carryforwards and associated deferred tax assets and expiration dates were estimated as follows (dollars in millions):

		Alliant Energy				IPL				WPL
	Earliest Expiration Date	Tax Carryforwards		Deferred Tax Assets		Tax Carryforwards		Deferred Tax Assets		Tax Carryforwards		Deferred Tax Assets
Federal net operating losses	2030		$527		$180		$231		$79		$218		$75
State net operating losses	2018	731		37		183		9		126		6
Federal tax credits	2022	227		224		80		78		89		87
					$441				$166				$168