Income Taxes (Tables)

12 Months Ended

Dec. 31, 2019

Income Tax [Line Items]

Schedule of Components of Income Tax Expense (Benefit)

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

	Alliant Energy									IPL									WPL
	2019			2018			2017			2019			2018			2017			2019			2018			2017
Current tax expense (benefit):
Federal		($6.6	)		($1.0	)		($41.0	)		($11.0	)		$14.9			($27.9	)		$12.0			($9.2	)		$5.5
State	24.2			(5.1		)	8.5			24.3			(7.1		)	1.6			13.7			(4.4		)	2.5
IPL’s tax benefit riders	(4.5		)	(13.2		)	(40.4		)	(4.5		)	(13.2		)	(40.4		)	—			—			—
Deferred tax expense (benefit):
Federal	69.7			67.9			159.5			26.4			9.5			72.5			30.7			43.8			55.0
State	41.4			29.8			12.3			30.9			7.3			(2.2		)	6.3			22.1			16.6
Production tax credits	(54.7		)	(29.5		)	(31.1		)	(41.8		)	(14.0		)	(14.1		)	(12.8		)	(15.5		)	(17.0		)
Investment tax credits	(0.8		)	(1.2		)	(1.1		)	(0.2		)	(0.6		)	(0.4		)	(0.6		)	(0.6		)	(0.7		)
		$68.7			$47.7			$66.7			$24.1			($3.2	)		($10.9	)		$49.3			$36.2			$61.9

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
	2019		2018		2017		2019		2018		2017		2019		2018		2017
Statutory federal income tax rate	21.0	%	21.0	%	35.0	%	21.0	%	21.0	%	35.0	%	21.0	%	21.0	%	35.0	%
State income taxes, net of federal benefits	6.8		7.0		5.5		8.5		7.7		6.5		6.2		6.2		5.1
Production tax credits	(8.6	)	(5.2	)	(6.1	)	(13.1	)	(5.2	)	(6.7	)	(4.5	)	(6.4	)	(7.1	)
Effect of rate-making on property-related differences	(6.1	)	(7.6	)	(8.5	)	(9.8	)	(14.0	)	(19.1	)	(2.7	)	(2.3	)	(1.7	)
Amortization of excess deferred taxes	(1.0	)	(0.3	)	(0.1	)	(0.3	)	—		(0.1	)	(1.8	)	(0.2	)	(0.1	)
IPL’s tax benefit riders	(0.7	)	(2.3	)	(7.6	)	(1.4	)	(4.9	)	(18.7	)	—		—		—
Adjustment for prior period taxes	0.6		(2.3	)	(1.5	)	3.1		(4.8	)	(3.4	)	(0.3	)	(0.2	)	—
Federal Tax Reform adjustments	—		(1.0	)	(3.4	)	—		(0.4	)	1.7		—		(2.3	)	(5.8	)
Other items, net	(1.2	)	(0.9	)	(0.8	)	(0.4	)	(0.6	)	(0.2	)	(0.4	)	(1.0	)	(0.5	)
Overall income tax rate	10.8	%	8.4	%	12.5	%	7.6	%	(1.2	%)	(5.0	%)	17.5	%	14.8	%	24.9	%

Schedule of Deferred Tax Assets and Liabilities

The deferred tax assets and liabilities included on the balance sheets at December 31 arise from the following temporary differences (in millions):

	Alliant Energy						IPL						WPL
	2019			2018			2019			2018			2019			2018
Deferred tax liabilities:
Property		$2,021.5			$1,975.5			$1,183.5			$1,158.4			$770.0			$735.2
ATC Holdings	110.8			102.4			—			—			—			—
Other	85.1			80.5			76.5			69.4			32.1			34.4
Total deferred tax liabilities	2,217.4			2,158.4			1,260.0			1,227.8			802.1			769.6
Deferred tax assets:
Federal credit carryforwards	355.4			299.1			175.0			133.2			160.3			147.4
Net operating losses carryforwards - federal	60.5			158.6			56.3			114.1			0.5			26.4
Net operating losses carryforwards - state	36.6			47.0			0.6			0.9			0.1			0.5
Other	60.5			59.8			20.6			22.8			15.8			14.1
Subtotal deferred tax assets	513.0			564.5			252.5			271.0			176.7			188.4
Valuation allowances	(9.6		)	(9.2		)	(0.5		)	(0.5		)	(0.8		)	(0.8		)
Total deferred tax assets	503.4			555.3			252.0			270.5			175.9			187.6
Total deferred tax liabilities, net		$1,714.0			$1,603.1			$1,008.0			$957.3			$626.2			$582.0

Summary Of Tax Credit Carryforwards

At December 31, 2019, carryforwards and expiration dates were estimated as follows (in millions):

	Range of Expiration Dates	Alliant Energy		IPL		WPL
Federal net operating losses	2037		$297		$276		$2
State net operating losses	2020-2039	615		9		2
Federal tax credits	2022-2039	355		175		160

Schedule Of Open Tax Years

Tax years that remain subject to the statute of limitations in the major jurisdictions for each of Alliant Energy, IPL and WPL are as follows:

Consolidated federal income tax returns (a)	2016	-	2018
Consolidated Iowa income tax returns (b)	2016	-	2018
Wisconsin combined tax returns (c)	2015	-	2018

(a) The 2016 and 2017 federal tax returns are effectively settled as a result of participation in the IRS Compliance Assurance Program, which allows Alliant Energy and the IRS to work together to resolve issues related to Alliant Energy’s current tax year before filing its federal income tax return. The statute of limitations for these federal tax returns expires three years from each filing date.

(b) The statute of limitations for these Iowa tax returns expires three years from each filing date.

(c)

The statute of limitations for these Wisconsin combined tax returns expires four years from each filing date.

IPL [Member]

Income Tax [Line Items]

Schedule of Components of Income Tax Expense (Benefit)

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

	Alliant Energy									IPL									WPL
	2019			2018			2017			2019			2018			2017			2019			2018			2017
Current tax expense (benefit):
Federal		($6.6	)		($1.0	)		($41.0	)		($11.0	)		$14.9			($27.9	)		$12.0			($9.2	)		$5.5
State	24.2			(5.1		)	8.5			24.3			(7.1		)	1.6			13.7			(4.4		)	2.5
IPL’s tax benefit riders	(4.5		)	(13.2		)	(40.4		)	(4.5		)	(13.2		)	(40.4		)	—			—			—
Deferred tax expense (benefit):
Federal	69.7			67.9			159.5			26.4			9.5			72.5			30.7			43.8			55.0
State	41.4			29.8			12.3			30.9			7.3			(2.2		)	6.3			22.1			16.6
Production tax credits	(54.7		)	(29.5		)	(31.1		)	(41.8		)	(14.0		)	(14.1		)	(12.8		)	(15.5		)	(17.0		)
Investment tax credits	(0.8		)	(1.2		)	(1.1		)	(0.2		)	(0.6		)	(0.4		)	(0.6		)	(0.6		)	(0.7		)
		$68.7			$47.7			$66.7			$24.1			($3.2	)		($10.9	)		$49.3			$36.2			$61.9

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
	2019		2018		2017		2019		2018		2017		2019		2018		2017
Statutory federal income tax rate	21.0	%	21.0	%	35.0	%	21.0	%	21.0	%	35.0	%	21.0	%	21.0	%	35.0	%
State income taxes, net of federal benefits	6.8		7.0		5.5		8.5		7.7		6.5		6.2		6.2		5.1
Production tax credits	(8.6	)	(5.2	)	(6.1	)	(13.1	)	(5.2	)	(6.7	)	(4.5	)	(6.4	)	(7.1	)
Effect of rate-making on property-related differences	(6.1	)	(7.6	)	(8.5	)	(9.8	)	(14.0	)	(19.1	)	(2.7	)	(2.3	)	(1.7	)
Amortization of excess deferred taxes	(1.0	)	(0.3	)	(0.1	)	(0.3	)	—		(0.1	)	(1.8	)	(0.2	)	(0.1	)
IPL’s tax benefit riders	(0.7	)	(2.3	)	(7.6	)	(1.4	)	(4.9	)	(18.7	)	—		—		—
Adjustment for prior period taxes	0.6		(2.3	)	(1.5	)	3.1		(4.8	)	(3.4	)	(0.3	)	(0.2	)	—
Federal Tax Reform adjustments	—		(1.0	)	(3.4	)	—		(0.4	)	1.7		—		(2.3	)	(5.8	)
Other items, net	(1.2	)	(0.9	)	(0.8	)	(0.4	)	(0.6	)	(0.2	)	(0.4	)	(1.0	)	(0.5	)
Overall income tax rate	10.8	%	8.4	%	12.5	%	7.6	%	(1.2	%)	(5.0	%)	17.5	%	14.8	%	24.9	%

Schedule of Deferred Tax Assets and Liabilities

The deferred tax assets and liabilities included on the balance sheets at December 31 arise from the following temporary differences (in millions):

	Alliant Energy						IPL						WPL
	2019			2018			2019			2018			2019			2018
Deferred tax liabilities:
Property		$2,021.5			$1,975.5			$1,183.5			$1,158.4			$770.0			$735.2
ATC Holdings	110.8			102.4			—			—			—			—
Other	85.1			80.5			76.5			69.4			32.1			34.4
Total deferred tax liabilities	2,217.4			2,158.4			1,260.0			1,227.8			802.1			769.6
Deferred tax assets:
Federal credit carryforwards	355.4			299.1			175.0			133.2			160.3			147.4
Net operating losses carryforwards - federal	60.5			158.6			56.3			114.1			0.5			26.4
Net operating losses carryforwards - state	36.6			47.0			0.6			0.9			0.1			0.5
Other	60.5			59.8			20.6			22.8			15.8			14.1
Subtotal deferred tax assets	513.0			564.5			252.5			271.0			176.7			188.4
Valuation allowances	(9.6		)	(9.2		)	(0.5		)	(0.5		)	(0.8		)	(0.8		)
Total deferred tax assets	503.4			555.3			252.0			270.5			175.9			187.6
Total deferred tax liabilities, net		$1,714.0			$1,603.1			$1,008.0			$957.3			$626.2			$582.0

Summary Of Tax Credit Carryforwards

At December 31, 2019, carryforwards and expiration dates were estimated as follows (in millions):

	Range of Expiration Dates	Alliant Energy		IPL		WPL
Federal net operating losses	2037		$297		$276		$2
State net operating losses	2020-2039	615		9		2
Federal tax credits	2022-2039	355		175		160

Schedule Of Open Tax Years

Tax years that remain subject to the statute of limitations in the major jurisdictions for each of Alliant Energy, IPL and WPL are as follows:

Consolidated federal income tax returns (a)	2016	-	2018
Consolidated Iowa income tax returns (b)	2016	-	2018
Wisconsin combined tax returns (c)	2015	-	2018

(a) The 2016 and 2017 federal tax returns are effectively settled as a result of participation in the IRS Compliance Assurance Program, which allows Alliant Energy and the IRS to work together to resolve issues related to Alliant Energy’s current tax year before filing its federal income tax return. The statute of limitations for these federal tax returns expires three years from each filing date.

(b) The statute of limitations for these Iowa tax returns expires three years from each filing date.

(c)

The statute of limitations for these Wisconsin combined tax returns expires four years from each filing date.

WPL [Member]

Income Tax [Line Items]

Schedule of Components of Income Tax Expense (Benefit)

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

	Alliant Energy									IPL									WPL
	2019			2018			2017			2019			2018			2017			2019			2018			2017
Current tax expense (benefit):
Federal		($6.6	)		($1.0	)		($41.0	)		($11.0	)		$14.9			($27.9	)		$12.0			($9.2	)		$5.5
State	24.2			(5.1		)	8.5			24.3			(7.1		)	1.6			13.7			(4.4		)	2.5
IPL’s tax benefit riders	(4.5		)	(13.2		)	(40.4		)	(4.5		)	(13.2		)	(40.4		)	—			—			—
Deferred tax expense (benefit):
Federal	69.7			67.9			159.5			26.4			9.5			72.5			30.7			43.8			55.0
State	41.4			29.8			12.3			30.9			7.3			(2.2		)	6.3			22.1			16.6
Production tax credits	(54.7		)	(29.5		)	(31.1		)	(41.8		)	(14.0		)	(14.1		)	(12.8		)	(15.5		)	(17.0		)
Investment tax credits	(0.8		)	(1.2		)	(1.1		)	(0.2		)	(0.6		)	(0.4		)	(0.6		)	(0.6		)	(0.7		)
		$68.7			$47.7			$66.7			$24.1			($3.2	)		($10.9	)		$49.3			$36.2			$61.9

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
	2019		2018		2017		2019		2018		2017		2019		2018		2017
Statutory federal income tax rate	21.0	%	21.0	%	35.0	%	21.0	%	21.0	%	35.0	%	21.0	%	21.0	%	35.0	%
State income taxes, net of federal benefits	6.8		7.0		5.5		8.5		7.7		6.5		6.2		6.2		5.1
Production tax credits	(8.6	)	(5.2	)	(6.1	)	(13.1	)	(5.2	)	(6.7	)	(4.5	)	(6.4	)	(7.1	)
Effect of rate-making on property-related differences	(6.1	)	(7.6	)	(8.5	)	(9.8	)	(14.0	)	(19.1	)	(2.7	)	(2.3	)	(1.7	)
Amortization of excess deferred taxes	(1.0	)	(0.3	)	(0.1	)	(0.3	)	—		(0.1	)	(1.8	)	(0.2	)	(0.1	)
IPL’s tax benefit riders	(0.7	)	(2.3	)	(7.6	)	(1.4	)	(4.9	)	(18.7	)	—		—		—
Adjustment for prior period taxes	0.6		(2.3	)	(1.5	)	3.1		(4.8	)	(3.4	)	(0.3	)	(0.2	)	—
Federal Tax Reform adjustments	—		(1.0	)	(3.4	)	—		(0.4	)	1.7		—		(2.3	)	(5.8	)
Other items, net	(1.2	)	(0.9	)	(0.8	)	(0.4	)	(0.6	)	(0.2	)	(0.4	)	(1.0	)	(0.5	)
Overall income tax rate	10.8	%	8.4	%	12.5	%	7.6	%	(1.2	%)	(5.0	%)	17.5	%	14.8	%	24.9	%

Schedule of Deferred Tax Assets and Liabilities

The deferred tax assets and liabilities included on the balance sheets at December 31 arise from the following temporary differences (in millions):

	Alliant Energy						IPL						WPL
	2019			2018			2019			2018			2019			2018
Deferred tax liabilities:
Property		$2,021.5			$1,975.5			$1,183.5			$1,158.4			$770.0			$735.2
ATC Holdings	110.8			102.4			—			—			—			—
Other	85.1			80.5			76.5			69.4			32.1			34.4
Total deferred tax liabilities	2,217.4			2,158.4			1,260.0			1,227.8			802.1			769.6
Deferred tax assets:
Federal credit carryforwards	355.4			299.1			175.0			133.2			160.3			147.4
Net operating losses carryforwards - federal	60.5			158.6			56.3			114.1			0.5			26.4
Net operating losses carryforwards - state	36.6			47.0			0.6			0.9			0.1			0.5
Other	60.5			59.8			20.6			22.8			15.8			14.1
Subtotal deferred tax assets	513.0			564.5			252.5			271.0			176.7			188.4
Valuation allowances	(9.6		)	(9.2		)	(0.5		)	(0.5		)	(0.8		)	(0.8		)
Total deferred tax assets	503.4			555.3			252.0			270.5			175.9			187.6
Total deferred tax liabilities, net		$1,714.0			$1,603.1			$1,008.0			$957.3			$626.2			$582.0

Summary Of Tax Credit Carryforwards

At December 31, 2019, carryforwards and expiration dates were estimated as follows (in millions):

	Range of Expiration Dates	Alliant Energy		IPL		WPL
Federal net operating losses	2037		$297		$276		$2
State net operating losses	2020-2039	615		9		2
Federal tax credits	2022-2039	355		175		160

Schedule Of Open Tax Years

Tax years that remain subject to the statute of limitations in the major jurisdictions for each of Alliant Energy, IPL and WPL are as follows:

Consolidated federal income tax returns (a)	2016	-	2018
Consolidated Iowa income tax returns (b)	2016	-	2018
Wisconsin combined tax returns (c)	2015	-	2018

(a) The 2016 and 2017 federal tax returns are effectively settled as a result of participation in the IRS Compliance Assurance Program, which allows Alliant Energy and the IRS to work together to resolve issues related to Alliant Energy’s current tax year before filing its federal income tax return. The statute of limitations for these federal tax returns expires three years from each filing date.

(b) The statute of limitations for these Iowa tax returns expires three years from each filing date.

(c)

The statute of limitations for these Wisconsin combined tax returns expires four years from each filing date.