Income Taxes (Tables)

12 Months Ended

Dec. 31, 2022

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
	2022	2021	2020	2022	2021	2020	2022	2021	2020
Current tax expense (benefit):
Federal	$7	$1	$1	($29)	($21)	$6	$46	$22	($11)
State	2	3	8	(8)	(1)	(1)	16	6	7
Deferred tax expense (benefit):
Federal	109	9	22	91	73	30	10	(75)	(9)
State	28	15	8	1	—	(2)	12	11	10
Production tax credits	(123)	(101)	(95)	(105)	(87)	(80)	(18)	(14)	(15)
Investment tax credits	(1)	(1)	(1)	—	—	—	—	(1)	(1)
	$22	($74)	($57)	($50)	($36)	($47)	$66	($51)	($19)

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 before income taxes.

	Alliant Energy			IPL			WPL
	2022	2021	2020	2022	2021	2020	2022	2021	2020
Statutory federal income tax rate	21%	21%	21%	21%	21%	21%	21%	21%	21%
State income taxes, net of federal benefits	3	2	2	(2)	(1)	(1)	6	6	6
Production tax credits	(18)	(17)	(17)	(34)	(27)	(28)	(5)	(6)	(7)
Amortization of excess deferred taxes (Refer to Note 2)	(2)	(18)	(13)	(2)	(4)	(5)	(3)	(43)	(26)
Effect of rate-making on property-related differences	(1)	(1)	(3)	(1)	(2)	(4)	(2)	(1)	(2)
Adjustment for prior period taxes	1	1	1	1	2	1	—	—	—
Other items, net	(1)	—	(1)	1	—	—	—	(1)	—
Overall income tax rate	3%	(12%)	(10%)	(16%)	(11%)	(16%)	17%	(24%)	(8%)

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
	2022	2021	2022	2021	2022	2021
Deferred tax liabilities:
Property	$2,442	$2,389	$1,440	$1,416	$938	$913
ATC Holdings	125	123	—	—	—	—
Other	155	111	86	76	80	50
Total deferred tax liabilities	2,722	2,623	1,526	1,492	1,018	963
Deferred tax assets:
Federal credit carryforwards	672	560	450	345	209	192
Net operating losses carryforwards - federal	—	39	—	36	—	—
Net operating losses carryforwards - state	32	38	—	3	—	—
Other	75	65	29	25	20	18
Subtotal deferred tax assets	779	702	479	409	229	210
Valuation allowances	—	(6)	—	—	—	—
Total deferred tax assets	779	696	479	409	229	210
Total deferred tax liabilities, net	$1,943	$1,927	$1,047	$1,083	$789	$753

Summary Of Tax Credit Carryforwards

At December 31, 2022, carryforwards and expiration dates were estimated as follows (in millions):

	Range of Expiration Dates	Alliant Energy	IPL	WPL
State net operating losses	2025-2042	$527	$10	$1
Federal tax credits	2024-2042	672	450	209

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)	2019	-	2021
Consolidated Iowa income tax returns (b)	2019	-	2021
Wisconsin combined tax returns (c)	2018	-	2021

(a)The 2019 and 2020 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
	2022	2021	2020	2022	2021	2020	2022	2021	2020
Current tax expense (benefit):
Federal	$7	$1	$1	($29)	($21)	$6	$46	$22	($11)
State	2	3	8	(8)	(1)	(1)	16	6	7
Deferred tax expense (benefit):
Federal	109	9	22	91	73	30	10	(75)	(9)
State	28	15	8	1	—	(2)	12	11	10
Production tax credits	(123)	(101)	(95)	(105)	(87)	(80)	(18)	(14)	(15)
Investment tax credits	(1)	(1)	(1)	—	—	—	—	(1)	(1)
	$22	($74)	($57)	($50)	($36)	($47)	$66	($51)	($19)

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 before income taxes.

	Alliant Energy			IPL			WPL
	2022	2021	2020	2022	2021	2020	2022	2021	2020
Statutory federal income tax rate	21%	21%	21%	21%	21%	21%	21%	21%	21%
State income taxes, net of federal benefits	3	2	2	(2)	(1)	(1)	6	6	6
Production tax credits	(18)	(17)	(17)	(34)	(27)	(28)	(5)	(6)	(7)
Amortization of excess deferred taxes (Refer to Note 2)	(2)	(18)	(13)	(2)	(4)	(5)	(3)	(43)	(26)
Effect of rate-making on property-related differences	(1)	(1)	(3)	(1)	(2)	(4)	(2)	(1)	(2)
Adjustment for prior period taxes	1	1	1	1	2	1	—	—	—
Other items, net	(1)	—	(1)	1	—	—	—	(1)	—
Overall income tax rate	3%	(12%)	(10%)	(16%)	(11%)	(16%)	17%	(24%)	(8%)

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
	2022	2021	2022	2021	2022	2021
Deferred tax liabilities:
Property	$2,442	$2,389	$1,440	$1,416	$938	$913
ATC Holdings	125	123	—	—	—	—
Other	155	111	86	76	80	50
Total deferred tax liabilities	2,722	2,623	1,526	1,492	1,018	963
Deferred tax assets:
Federal credit carryforwards	672	560	450	345	209	192
Net operating losses carryforwards - federal	—	39	—	36	—	—
Net operating losses carryforwards - state	32	38	—	3	—	—
Other	75	65	29	25	20	18
Subtotal deferred tax assets	779	702	479	409	229	210
Valuation allowances	—	(6)	—	—	—	—
Total deferred tax assets	779	696	479	409	229	210
Total deferred tax liabilities, net	$1,943	$1,927	$1,047	$1,083	$789	$753

Summary Of Tax Credit Carryforwards

At December 31, 2022, carryforwards and expiration dates were estimated as follows (in millions):

	Range of Expiration Dates	Alliant Energy	IPL	WPL
State net operating losses	2025-2042	$527	$10	$1
Federal tax credits	2024-2042	672	450	209

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)	2019	-	2021
Consolidated Iowa income tax returns (b)	2019	-	2021
Wisconsin combined tax returns (c)	2018	-	2021

(a)The 2019 and 2020 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
	2022	2021	2020	2022	2021	2020	2022	2021	2020
Current tax expense (benefit):
Federal	$7	$1	$1	($29)	($21)	$6	$46	$22	($11)
State	2	3	8	(8)	(1)	(1)	16	6	7
Deferred tax expense (benefit):
Federal	109	9	22	91	73	30	10	(75)	(9)
State	28	15	8	1	—	(2)	12	11	10
Production tax credits	(123)	(101)	(95)	(105)	(87)	(80)	(18)	(14)	(15)
Investment tax credits	(1)	(1)	(1)	—	—	—	—	(1)	(1)
	$22	($74)	($57)	($50)	($36)	($47)	$66	($51)	($19)

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 before income taxes.

	Alliant Energy			IPL			WPL
	2022	2021	2020	2022	2021	2020	2022	2021	2020
Statutory federal income tax rate	21%	21%	21%	21%	21%	21%	21%	21%	21%
State income taxes, net of federal benefits	3	2	2	(2)	(1)	(1)	6	6	6
Production tax credits	(18)	(17)	(17)	(34)	(27)	(28)	(5)	(6)	(7)
Amortization of excess deferred taxes (Refer to Note 2)	(2)	(18)	(13)	(2)	(4)	(5)	(3)	(43)	(26)
Effect of rate-making on property-related differences	(1)	(1)	(3)	(1)	(2)	(4)	(2)	(1)	(2)
Adjustment for prior period taxes	1	1	1	1	2	1	—	—	—
Other items, net	(1)	—	(1)	1	—	—	—	(1)	—
Overall income tax rate	3%	(12%)	(10%)	(16%)	(11%)	(16%)	17%	(24%)	(8%)

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
	2022	2021	2022	2021	2022	2021
Deferred tax liabilities:
Property	$2,442	$2,389	$1,440	$1,416	$938	$913
ATC Holdings	125	123	—	—	—	—
Other	155	111	86	76	80	50
Total deferred tax liabilities	2,722	2,623	1,526	1,492	1,018	963
Deferred tax assets:
Federal credit carryforwards	672	560	450	345	209	192
Net operating losses carryforwards - federal	—	39	—	36	—	—
Net operating losses carryforwards - state	32	38	—	3	—	—
Other	75	65	29	25	20	18
Subtotal deferred tax assets	779	702	479	409	229	210
Valuation allowances	—	(6)	—	—	—	—
Total deferred tax assets	779	696	479	409	229	210
Total deferred tax liabilities, net	$1,943	$1,927	$1,047	$1,083	$789	$753

Summary Of Tax Credit Carryforwards

At December 31, 2022, carryforwards and expiration dates were estimated as follows (in millions):

	Range of Expiration Dates	Alliant Energy	IPL	WPL
State net operating losses	2025-2042	$527	$10	$1
Federal tax credits	2024-2042	672	450	209

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)	2019	-	2021
Consolidated Iowa income tax returns (b)	2019	-	2021
Wisconsin combined tax returns (c)	2018	-	2021

(a)The 2019 and 2020 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.