Income Taxes (Tables)

12 Months Ended

Dec. 31, 2012

Income Tax [Line Items]

Schedule of Components of Income Tax Expense (Benefit)

The components of “Income tax expense (benefit)” in the Consolidated Statements of Income were as follows (in millions):

	Alliant Energy									IPL									WPL
	2012			2011			2010			2012			2011			2010			2012			2011			2010
Current tax expense (benefit):
Federal		($29.3	)		$58.6			$7.1			($7.7	)		$54.5			($22.4	)		$7.2			($4.3	)		$26.8
State	11.6			15.7			10.6			9.1			20.0			(7.6		)	(0.9		)	(7.1		)	14.7
IPL’s electric tax benefit rider	(48.3		)	(35.9		)	—			(48.3		)	(35.9		)	—			—			—			—
Deferred tax expense (benefit):
Federal	157.8			99.0			165.5			37.4			(11.6		)	100.9			81.1			111.3			63.3
State	23.9			(16.8		)	4.9			3.2			(16.4		)	(2.8		)	20.3			19.0			6.6
Production tax credits	(24.8		)	(27.1		)	(11.2		)	(12.5		)	(12.3		)	(7.7		)	(12.3		)	(14.8		)	(3.5		)
Investment tax credits	(1.7		)	(1.8		)	(1.8		)	(0.6		)	(0.6		)	(0.6		)	(1.1		)	(1.2		)	(1.2		)
Provision recorded as a change in uncertain tax positions:
Current	8.0			16.3			(84.0		)	8.1			16.6			(41.1		)	(0.1		)	(0.3		)	(41.7		)
Deferred	(7.6		)	(38.3		)	59.6			(8.2		)	(17.6		)	26.2			0.6			(20.7		)	33.3
Provision recorded as a change in accrued interest	(0.2		)	(0.5		)	(3.0		)	(0.3		)	(0.3		)	(2.6		)	(0.2		)	—			—
		$89.4			$69.2			$147.7			($19.8	)		($3.6	)		$42.3			$94.6			$81.9			$98.3

Schedule Of Effective 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
	2012		2011		2010		2012		2011		2010		2012		2011		2010
Statutory federal income tax rate	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%
State income taxes, net of federal benefits	5.7		4.6		4.8		5.8		4.3		4.1		5.5		5.0		5.1
State apportionment change due to announced sale of RMT	3.5		—		—		6.2		—		—		2.7		—		—
IPL’s electric tax benefit rider	(11.2	)	(8.8	)	—		(37.0	)	(26.5	)	—		—		—		—
Production tax credits	(5.8	)	(6.6	)	(2.4	)	(9.6	)	(9.1	)	(4.1	)	(4.7	)	(6.0	)	(1.4	)
Effect of rate-making on property-related differences	(5.0	)	(2.0	)	(4.2	)	(14.2	)	(5.3	)	(8.9	)	(1.1	)	(0.5	)	(1.1	)
Adjustment of prior period taxes	—		0.2		0.3		0.2		1.7		(1.8	)	(0.3	)	—		2.0
Wisconsin tax legislation	—		(4.6	)	—		—		—		—		—		—		—
Federal Health Care Legislation	—		—		1.6		—		—		2.0		—		—		1.2
Other items, net	(1.4	)	(0.9	)	(2.8	)	(1.6	)	(2.8	)	(3.5	)	(0.8	)	(0.1	)	(1.6	)
Overall income tax rate	20.8	%	16.9	%	32.3	%	(15.2	%)	(2.7	%)	22.8	%	36.3	%	33.4	%	39.2	%

Production Tax Credits (Net Of State Tax Impacts)

Production tax credits (net of state tax impacts) resulting from these wind projects were as follows (in millions):

	Alliant Energy								IPL						WPL
	2012			2011		2010			2012		2011		2010		2012			2011		2010
Whispering Willow - East (IPL)		$12.5			$12.3		$7.7			$12.5		$12.3		$7.7		$—			$—		$—
Bent Tree - Phase I (WPL) (a)	9.3			9.3		1.2			—		—		—		9.3			9.3		1.2
Cedar Ridge (WPL)	4.0			4.5		3.3			—		—		—		4.0			4.5		3.3
	25.8			26.1		12.2			12.5		12.3		7.7		13.3			13.8		4.5
Deferral (a)	(1.0		)	1.0		(1.0		)	—		—		—		(1.0		)	1.0		(1.0		)
		$24.8			$27.1		$11.2			$12.5		$12.3		$7.7		$12.3			$14.8		$3.5

(a) In 2010 and 2012, WPL deferred the retail portion of the production tax credits generated in 2010 from its Bent Tree - Phase I wind project pursuant to orders issued by the PSCW in December 2009 and July 2012, respectively. As a result of a regulatory assessment completed in 2011, the retail portion of the production tax credit deferral recorded in 2010 was reversed.

Schedule of Deferred Tax Assets and Liabilities

The deferred income tax (assets) and liabilities included on Alliant Energy’s Consolidated Balance Sheets at December 31 arise from the following temporary differences (in millions):

	2012								2011
	Deferred			Deferred Tax					Deferred			Deferred Tax
Alliant Energy	Tax Assets			Liabilities		Net			Tax Assets			Liabilities		Net
Property		$—			$2,143.8		$2,143.8			$—			$1,926.4		$1,926.4
Investment in ATC	—			104.3		104.3			—			93.8		93.8
Deferred portion of tax gain on IPL’s electric transmission assets sale	—			50.7		50.7			—			75.5		75.5
Net operating losses carryforward - state	(46.8		)	—		(46.8		)	(39.9		)	—		(39.9		)
Federal credit carryforward	(133.8		)	—		(133.8		)	(107.4		)	—		(107.4		)
Regulatory liability - IPL’s tax benefit rider	(144.6		)	—		(144.6		)	(140.6		)	—		(140.6		)
Net operating losses carryforward - federal	(306.0		)	—		(306.0		)	(336.1		)	—		(336.1		)
Other	(113.7		)	208.2		94.5			(128.2		)	224.7		96.5
Subtotal	(744.9		)	2,507.0		1,762.1			(752.2		)	2,320.4		1,568.2
Valuation allowances	1.9			—		1.9			1.2			—		1.2
		($743.0	)		$2,507.0		$1,764.0			($751.0	)		$2,320.4		$1,569.4

	2012			2011
Other current assets		($170.2	)		($22.8	)
Deferred income taxes	1,934.2			1,592.2
Total deferred tax liabilities		$1,764.0			$1,569.4

Summary Of Tax Credit Carryforwards

At December 31, 2012, tax carryforwards and associated deferred tax assets and expiration dates were estimated as follows (in millions):

Alliant Energy	Tax Carryforwards		Deferred Tax Assets		Earliest Expiration Date
Federal net operating losses		$892		$306	2029
State net operating losses	871		47		2014
Federal tax credits	136		134		2022
				$487

IPL	Tax Carryforwards		Deferred Tax Assets		Earliest Expiration Date
Federal net operating losses		$382		$131	2029
State net operating losses	254		15		2018
Federal tax credits	38		37		2022
				$183

WPL	Tax Carryforwards		Deferred Tax Assets		Earliest Expiration Date
Federal net operating losses		$414		$142	2029
State net operating losses	152		8		2018
Federal tax credits	40		39		2022
				$189

Summary of Uncertain Tax Positions

A reconciliation of the beginning and ending amounts of uncertain tax positions, excluding interest, is as follows (in millions):

	Alliant Energy									IPL									WPL
	2012			2011			2010			2012			2011			2010			2012			2011			2010
Balance, January 1		$23.5			$66.7			$101.7			$10.9			$33.0			$58.4			$12.6			$33.7			$42.1
Additions based on tax positions related to the current year	0.7			0.7			3.8			—			0.1			2.5			0.7			0.6			1.3
Additions for tax positions of prior years (a)	—			—			9.1			—			—			3.8			—			—			5.2
Reductions for tax positions of prior years (b)	(23.5		)	(43.9		)	(31.8		)	(10.9		)	(22.2		)	(22.7		)	(12.6		)	(21.7		)	(8.0		)
Settlements with taxing authorities	—			—			(16.1		)	—			—			(9.0		)	—			—			(6.9		)
Balance, December 31 (c)		$0.7			$23.5			$66.7			$—			$10.9			$33.0			$0.7			$12.6			$33.7

(a) The additions for tax positions of prior years were related to positions taken by Alliant Energy, IPL and WPL on their federal and state tax returns related to the capitalization and dispositions of property.

(b) In 2012, the reductions for tax positions of prior years were due to the finalization of Alliant Energy’s federal income tax return audits for calendar years 2005 through 2009. In 2011, the reductions for tax positions of prior years were related to guidance published by the IRS clarifying the treatment of repair expenditures for electric distribution property. In 2010, the reductions of tax positions of prior years were primarily related to deductions taken by Alliant Energy, IPL and WPL on their federal and state tax returns that were settled under audit for amounts less than the reductions of tax positions recorded.

(c) At December 31, 2012 and 2011, $0 and $10 million, respectively, of uncertain tax positions balances for both Alliant Energy and IPL included amounts recorded in regulatory liability accounts.

At December 31, 2012, 2011 and 2010, there were no penalties accrued related to uncertain tax positions. Additional information regarding uncertain tax positions at December 31 is as follows (in millions):

	Alliant Energy						IPL						WPL
	2012		2011		2010		2012		2011		2010		2012		2011		2010
Tax positions favorably impacting future effective tax rates for continuing operations		$0.7		$—		$—		$—		$—		$—		$0.7		$—		$—
Interest accrued	—		0.4		0.7		—		0.4		0.7		—		—		—

Schedule Of Open Tax Years

Open tax years - Tax years that remain subject to the statute of limitations are as follows:

Major Jurisdiction	Alliant Energy			IPL			WPL
Consolidated federal income tax returns (a)	2005	-	2011	2005	-	2011	2005	-	2011
Consolidated Iowa income tax returns (b)	2005	-	2011	2005	-	2011	2005	-	2011
Wisconsin income tax returns	2005	-	2008	N/A			2005	-	2008
Wisconsin combined tax returns	2009	-	2011	2009	-	2011	2009	-	2011

(a) 2005 through 2010 are effectively settled. The statute of limitations for 2005 through 2008 has been extended to June 30, 2013. The statute of limitations for 2009 through 2011 expires three years from the extended due date of the federal tax return.

(b) 2005 through 2008 are open for federal audit adjustments only.

IPL [Member]

Income Tax [Line Items]

Schedule of Components of Income Tax Expense (Benefit)

The components of “Income tax expense (benefit)” in the Consolidated Statements of Income were as follows (in millions):

	Alliant Energy									IPL									WPL
	2012			2011			2010			2012			2011			2010			2012			2011			2010
Current tax expense (benefit):
Federal		($29.3	)		$58.6			$7.1			($7.7	)		$54.5			($22.4	)		$7.2			($4.3	)		$26.8
State	11.6			15.7			10.6			9.1			20.0			(7.6		)	(0.9		)	(7.1		)	14.7
IPL’s electric tax benefit rider	(48.3		)	(35.9		)	—			(48.3		)	(35.9		)	—			—			—			—
Deferred tax expense (benefit):
Federal	157.8			99.0			165.5			37.4			(11.6		)	100.9			81.1			111.3			63.3
State	23.9			(16.8		)	4.9			3.2			(16.4		)	(2.8		)	20.3			19.0			6.6
Production tax credits	(24.8		)	(27.1		)	(11.2		)	(12.5		)	(12.3		)	(7.7		)	(12.3		)	(14.8		)	(3.5		)
Investment tax credits	(1.7		)	(1.8		)	(1.8		)	(0.6		)	(0.6		)	(0.6		)	(1.1		)	(1.2		)	(1.2		)
Provision recorded as a change in uncertain tax positions:
Current	8.0			16.3			(84.0		)	8.1			16.6			(41.1		)	(0.1		)	(0.3		)	(41.7		)
Deferred	(7.6		)	(38.3		)	59.6			(8.2		)	(17.6		)	26.2			0.6			(20.7		)	33.3
Provision recorded as a change in accrued interest	(0.2		)	(0.5		)	(3.0		)	(0.3		)	(0.3		)	(2.6		)	(0.2		)	—			—
		$89.4			$69.2			$147.7			($19.8	)		($3.6	)		$42.3			$94.6			$81.9			$98.3

Schedule Of Effective 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
	2012		2011		2010		2012		2011		2010		2012		2011		2010
Statutory federal income tax rate	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%
State income taxes, net of federal benefits	5.7		4.6		4.8		5.8		4.3		4.1		5.5		5.0		5.1
State apportionment change due to announced sale of RMT	3.5		—		—		6.2		—		—		2.7		—		—
IPL’s electric tax benefit rider	(11.2	)	(8.8	)	—		(37.0	)	(26.5	)	—		—		—		—
Production tax credits	(5.8	)	(6.6	)	(2.4	)	(9.6	)	(9.1	)	(4.1	)	(4.7	)	(6.0	)	(1.4	)
Effect of rate-making on property-related differences	(5.0	)	(2.0	)	(4.2	)	(14.2	)	(5.3	)	(8.9	)	(1.1	)	(0.5	)	(1.1	)
Adjustment of prior period taxes	—		0.2		0.3		0.2		1.7		(1.8	)	(0.3	)	—		2.0
Wisconsin tax legislation	—		(4.6	)	—		—		—		—		—		—		—
Federal Health Care Legislation	—		—		1.6		—		—		2.0		—		—		1.2
Other items, net	(1.4	)	(0.9	)	(2.8	)	(1.6	)	(2.8	)	(3.5	)	(0.8	)	(0.1	)	(1.6	)
Overall income tax rate	20.8	%	16.9	%	32.3	%	(15.2	%)	(2.7	%)	22.8	%	36.3	%	33.4	%	39.2	%

Production Tax Credits (Net Of State Tax Impacts)

Production tax credits (net of state tax impacts) resulting from these wind projects were as follows (in millions):

	Alliant Energy								IPL						WPL
	2012			2011		2010			2012		2011		2010		2012			2011		2010
Whispering Willow - East (IPL)		$12.5			$12.3		$7.7			$12.5		$12.3		$7.7		$—			$—		$—
Bent Tree - Phase I (WPL) (a)	9.3			9.3		1.2			—		—		—		9.3			9.3		1.2
Cedar Ridge (WPL)	4.0			4.5		3.3			—		—		—		4.0			4.5		3.3
	25.8			26.1		12.2			12.5		12.3		7.7		13.3			13.8		4.5
Deferral (a)	(1.0		)	1.0		(1.0		)	—		—		—		(1.0		)	1.0		(1.0		)
		$24.8			$27.1		$11.2			$12.5		$12.3		$7.7		$12.3			$14.8		$3.5

(a) In 2010 and 2012, WPL deferred the retail portion of the production tax credits generated in 2010 from its Bent Tree - Phase I wind project pursuant to orders issued by the PSCW in December 2009 and July 2012, respectively. As a result of a regulatory assessment completed in 2011, the retail portion of the production tax credit deferral recorded in 2010 was reversed.

Schedule of Deferred Tax Assets and Liabilities

The deferred income tax (assets) and liabilities included on IPL’s Consolidated Balance Sheets at December 31 arise from the following temporary differences (in millions):

	2012								2011
	Deferred			Deferred Tax					Deferred			Deferred Tax
IPL	Tax Assets			Liabilities		Net			Tax Assets			Liabilities		Net
Property		$—			$1,243.9		$1,243.9			$—			$1,134.1		$1,134.1
Pension and other postretirement benefits obligations	—			64.9		64.9			—			67.6		67.6
Deferred portion of tax gain on electric transmission assets sale	—			50.7		50.7			—			75.5		75.5
Federal credit carryforward	(37.4		)	—		(37.4		)	(25.0		)	—		(25.0		)
Net operating losses carryforward - federal	(131.0		)	—		(131.0		)	(154.4		)	—		(154.4		)
Regulatory liability - tax benefit rider	(144.6		)	—		(144.6		)	(140.6		)	—		(140.6		)
Other	(70.4		)	31.9		(38.5		)	(76.5		)	42.7		(33.8		)
		($383.4	)		$1,391.4		$1,008.0			($396.5	)		$1,319.9		$923.4

	2012			2011
Other current assets		($79.3	)		($13.5	)
Deferred income taxes	1,087.3			936.9
Total deferred tax liabilities		$1,008.0			$923.4

Summary Of Tax Credit Carryforwards

At December 31, 2012, tax carryforwards and associated deferred tax assets and expiration dates were estimated as follows (in millions):

Alliant Energy	Tax Carryforwards		Deferred Tax Assets		Earliest Expiration Date
Federal net operating losses		$892		$306	2029
State net operating losses	871		47		2014
Federal tax credits	136		134		2022
				$487

IPL	Tax Carryforwards		Deferred Tax Assets		Earliest Expiration Date
Federal net operating losses		$382		$131	2029
State net operating losses	254		15		2018
Federal tax credits	38		37		2022
				$183

WPL	Tax Carryforwards		Deferred Tax Assets		Earliest Expiration Date
Federal net operating losses		$414		$142	2029
State net operating losses	152		8		2018
Federal tax credits	40		39		2022
				$189

Summary of Uncertain Tax Positions

A reconciliation of the beginning and ending amounts of uncertain tax positions, excluding interest, is as follows (in millions):

	Alliant Energy									IPL									WPL
	2012			2011			2010			2012			2011			2010			2012			2011			2010
Balance, January 1		$23.5			$66.7			$101.7			$10.9			$33.0			$58.4			$12.6			$33.7			$42.1
Additions based on tax positions related to the current year	0.7			0.7			3.8			—			0.1			2.5			0.7			0.6			1.3
Additions for tax positions of prior years (a)	—			—			9.1			—			—			3.8			—			—			5.2
Reductions for tax positions of prior years (b)	(23.5		)	(43.9		)	(31.8		)	(10.9		)	(22.2		)	(22.7		)	(12.6		)	(21.7		)	(8.0		)
Settlements with taxing authorities	—			—			(16.1		)	—			—			(9.0		)	—			—			(6.9		)
Balance, December 31 (c)		$0.7			$23.5			$66.7			$—			$10.9			$33.0			$0.7			$12.6			$33.7

(a) The additions for tax positions of prior years were related to positions taken by Alliant Energy, IPL and WPL on their federal and state tax returns related to the capitalization and dispositions of property.

(b) In 2012, the reductions for tax positions of prior years were due to the finalization of Alliant Energy’s federal income tax return audits for calendar years 2005 through 2009. In 2011, the reductions for tax positions of prior years were related to guidance published by the IRS clarifying the treatment of repair expenditures for electric distribution property. In 2010, the reductions of tax positions of prior years were primarily related to deductions taken by Alliant Energy, IPL and WPL on their federal and state tax returns that were settled under audit for amounts less than the reductions of tax positions recorded.

(c) At December 31, 2012 and 2011, $0 and $10 million, respectively, of uncertain tax positions balances for both Alliant Energy and IPL included amounts recorded in regulatory liability accounts.

At December 31, 2012, 2011 and 2010, there were no penalties accrued related to uncertain tax positions. Additional information regarding uncertain tax positions at December 31 is as follows (in millions):

	Alliant Energy						IPL						WPL
	2012		2011		2010		2012		2011		2010		2012		2011		2010
Tax positions favorably impacting future effective tax rates for continuing operations		$0.7		$—		$—		$—		$—		$—		$0.7		$—		$—
Interest accrued	—		0.4		0.7		—		0.4		0.7		—		—		—

Schedule Of Open Tax Years

Open tax years - Tax years that remain subject to the statute of limitations are as follows:

Major Jurisdiction	Alliant Energy			IPL			WPL
Consolidated federal income tax returns (a)	2005	-	2011	2005	-	2011	2005	-	2011
Consolidated Iowa income tax returns (b)	2005	-	2011	2005	-	2011	2005	-	2011
Wisconsin income tax returns	2005	-	2008	N/A			2005	-	2008
Wisconsin combined tax returns	2009	-	2011	2009	-	2011	2009	-	2011

(a) 2005 through 2010 are effectively settled. The statute of limitations for 2005 through 2008 has been extended to June 30, 2013. The statute of limitations for 2009 through 2011 expires three years from the extended due date of the federal tax return.

(b) 2005 through 2008 are open for federal audit adjustments only.

WPL [Member]

Income Tax [Line Items]

Schedule of Components of Income Tax Expense (Benefit)

The components of “Income tax expense (benefit)” in the Consolidated Statements of Income were as follows (in millions):

	Alliant Energy									IPL									WPL
	2012			2011			2010			2012			2011			2010			2012			2011			2010
Current tax expense (benefit):
Federal		($29.3	)		$58.6			$7.1			($7.7	)		$54.5			($22.4	)		$7.2			($4.3	)		$26.8
State	11.6			15.7			10.6			9.1			20.0			(7.6		)	(0.9		)	(7.1		)	14.7
IPL’s electric tax benefit rider	(48.3		)	(35.9		)	—			(48.3		)	(35.9		)	—			—			—			—
Deferred tax expense (benefit):
Federal	157.8			99.0			165.5			37.4			(11.6		)	100.9			81.1			111.3			63.3
State	23.9			(16.8		)	4.9			3.2			(16.4		)	(2.8		)	20.3			19.0			6.6
Production tax credits	(24.8		)	(27.1		)	(11.2		)	(12.5		)	(12.3		)	(7.7		)	(12.3		)	(14.8		)	(3.5		)
Investment tax credits	(1.7		)	(1.8		)	(1.8		)	(0.6		)	(0.6		)	(0.6		)	(1.1		)	(1.2		)	(1.2		)
Provision recorded as a change in uncertain tax positions:
Current	8.0			16.3			(84.0		)	8.1			16.6			(41.1		)	(0.1		)	(0.3		)	(41.7		)
Deferred	(7.6		)	(38.3		)	59.6			(8.2		)	(17.6		)	26.2			0.6			(20.7		)	33.3
Provision recorded as a change in accrued interest	(0.2		)	(0.5		)	(3.0		)	(0.3		)	(0.3		)	(2.6		)	(0.2		)	—			—
		$89.4			$69.2			$147.7			($19.8	)		($3.6	)		$42.3			$94.6			$81.9			$98.3

Schedule Of Effective 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
	2012		2011		2010		2012		2011		2010		2012		2011		2010
Statutory federal income tax rate	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%	35.0	%
State income taxes, net of federal benefits	5.7		4.6		4.8		5.8		4.3		4.1		5.5		5.0		5.1
State apportionment change due to announced sale of RMT	3.5		—		—		6.2		—		—		2.7		—		—
IPL’s electric tax benefit rider	(11.2	)	(8.8	)	—		(37.0	)	(26.5	)	—		—		—		—
Production tax credits	(5.8	)	(6.6	)	(2.4	)	(9.6	)	(9.1	)	(4.1	)	(4.7	)	(6.0	)	(1.4	)
Effect of rate-making on property-related differences	(5.0	)	(2.0	)	(4.2	)	(14.2	)	(5.3	)	(8.9	)	(1.1	)	(0.5	)	(1.1	)
Adjustment of prior period taxes	—		0.2		0.3		0.2		1.7		(1.8	)	(0.3	)	—		2.0
Wisconsin tax legislation	—		(4.6	)	—		—		—		—		—		—		—
Federal Health Care Legislation	—		—		1.6		—		—		2.0		—		—		1.2
Other items, net	(1.4	)	(0.9	)	(2.8	)	(1.6	)	(2.8	)	(3.5	)	(0.8	)	(0.1	)	(1.6	)
Overall income tax rate	20.8	%	16.9	%	32.3	%	(15.2	%)	(2.7	%)	22.8	%	36.3	%	33.4	%	39.2	%

Production Tax Credits (Net Of State Tax Impacts)

Production tax credits (net of state tax impacts) resulting from these wind projects were as follows (in millions):

	Alliant Energy								IPL						WPL
	2012			2011		2010			2012		2011		2010		2012			2011		2010
Whispering Willow - East (IPL)		$12.5			$12.3		$7.7			$12.5		$12.3		$7.7		$—			$—		$—
Bent Tree - Phase I (WPL) (a)	9.3			9.3		1.2			—		—		—		9.3			9.3		1.2
Cedar Ridge (WPL)	4.0			4.5		3.3			—		—		—		4.0			4.5		3.3
	25.8			26.1		12.2			12.5		12.3		7.7		13.3			13.8		4.5
Deferral (a)	(1.0		)	1.0		(1.0		)	—		—		—		(1.0		)	1.0		(1.0		)
		$24.8			$27.1		$11.2			$12.5		$12.3		$7.7		$12.3			$14.8		$3.5

(a) In 2010 and 2012, WPL deferred the retail portion of the production tax credits generated in 2010 from its Bent Tree - Phase I wind project pursuant to orders issued by the PSCW in December 2009 and July 2012, respectively. As a result of a regulatory assessment completed in 2011, the retail portion of the production tax credit deferral recorded in 2010 was reversed.

Schedule of Deferred Tax Assets and Liabilities

The deferred income tax (assets) and liabilities included on WPL’s Consolidated Balance Sheets at December 31 arise from the following temporary differences (in millions):

	2012								2011
	Deferred			Deferred Tax					Deferred			Deferred Tax
WPL	Tax Assets			Liabilities		Net			Tax Assets			Liabilities		Net
Property		$—			$793.3		$793.3			$—			$697.1		$697.1
Investment in ATC	—			104.3		104.3			—			93.8		93.8
Pension and other postretirement benefits obligations	—			46.4		46.4			—			49.6		49.6
Customer advances	(9.6		)	—		(9.6		)	(11.6		)	—		(11.6		)
Federal credit carryforward	(39.4		)	—		(39.4		)	(26.1		)	—		(26.1		)
Net operating losses carryforward - federal	(142.2		)	—		(142.2		)	(141.1		)	—		(141.1		)
Other	(31.6		)	37.3		5.7			(29.3		)	34.1		4.8
		($222.8	)		$981.3		$758.5			($208.1	)		$874.6		$666.5

	2012			2011
Other current assets		($85.6	)		($6.0	)
Deferred income taxes	844.1			672.5
Total deferred tax liabilities		$758.5			$666.5

Summary Of Tax Credit Carryforwards

At December 31, 2012, tax carryforwards and associated deferred tax assets and expiration dates were estimated as follows (in millions):

Alliant Energy	Tax Carryforwards		Deferred Tax Assets		Earliest Expiration Date
Federal net operating losses		$892		$306	2029
State net operating losses	871		47		2014
Federal tax credits	136		134		2022
				$487

IPL	Tax Carryforwards		Deferred Tax Assets		Earliest Expiration Date
Federal net operating losses		$382		$131	2029
State net operating losses	254		15		2018
Federal tax credits	38		37		2022
				$183

WPL	Tax Carryforwards		Deferred Tax Assets		Earliest Expiration Date
Federal net operating losses		$414		$142	2029
State net operating losses	152		8		2018
Federal tax credits	40		39		2022
				$189

Summary of Uncertain Tax Positions

A reconciliation of the beginning and ending amounts of uncertain tax positions, excluding interest, is as follows (in millions):

	Alliant Energy									IPL									WPL
	2012			2011			2010			2012			2011			2010			2012			2011			2010
Balance, January 1		$23.5			$66.7			$101.7			$10.9			$33.0			$58.4			$12.6			$33.7			$42.1
Additions based on tax positions related to the current year	0.7			0.7			3.8			—			0.1			2.5			0.7			0.6			1.3
Additions for tax positions of prior years (a)	—			—			9.1			—			—			3.8			—			—			5.2
Reductions for tax positions of prior years (b)	(23.5		)	(43.9		)	(31.8		)	(10.9		)	(22.2		)	(22.7		)	(12.6		)	(21.7		)	(8.0		)
Settlements with taxing authorities	—			—			(16.1		)	—			—			(9.0		)	—			—			(6.9		)
Balance, December 31 (c)		$0.7			$23.5			$66.7			$—			$10.9			$33.0			$0.7			$12.6			$33.7

(a) The additions for tax positions of prior years were related to positions taken by Alliant Energy, IPL and WPL on their federal and state tax returns related to the capitalization and dispositions of property.

(b) In 2012, the reductions for tax positions of prior years were due to the finalization of Alliant Energy’s federal income tax return audits for calendar years 2005 through 2009. In 2011, the reductions for tax positions of prior years were related to guidance published by the IRS clarifying the treatment of repair expenditures for electric distribution property. In 2010, the reductions of tax positions of prior years were primarily related to deductions taken by Alliant Energy, IPL and WPL on their federal and state tax returns that were settled under audit for amounts less than the reductions of tax positions recorded.

(c) At December 31, 2012 and 2011, $0 and $10 million, respectively, of uncertain tax positions balances for both Alliant Energy and IPL included amounts recorded in regulatory liability accounts.

At December 31, 2012, 2011 and 2010, there were no penalties accrued related to uncertain tax positions. Additional information regarding uncertain tax positions at December 31 is as follows (in millions):

	Alliant Energy						IPL						WPL
	2012		2011		2010		2012		2011		2010		2012		2011		2010
Tax positions favorably impacting future effective tax rates for continuing operations		$0.7		$—		$—		$—		$—		$—		$0.7		$—		$—
Interest accrued	—		0.4		0.7		—		0.4		0.7		—		—		—

Schedule Of Open Tax Years

Open tax years - Tax years that remain subject to the statute of limitations are as follows:

Major Jurisdiction	Alliant Energy			IPL			WPL
Consolidated federal income tax returns (a)	2005	-	2011	2005	-	2011	2005	-	2011
Consolidated Iowa income tax returns (b)	2005	-	2011	2005	-	2011	2005	-	2011
Wisconsin income tax returns	2005	-	2008	N/A			2005	-	2008
Wisconsin combined tax returns	2009	-	2011	2009	-	2011	2009	-	2011

(a) 2005 through 2010 are effectively settled. The statute of limitations for 2005 through 2008 has been extended to June 30, 2013. The statute of limitations for 2009 through 2011 expires three years from the extended due date of the federal tax return.

(b) 2005 through 2008 are open for federal audit adjustments only.