Income Taxes (Tables)

12 Months Ended

Dec. 31, 2021

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
	2021	2020	2019	2021	2020	2019	2021	2020	2019
Current tax expense (benefit):
Federal	$1	$1	($7)	($21)	$6	($11)	$22	($11)	$12
State	3	8	24	(1)	(1)	24	6	7	13
IPL’s tax benefit riders	—	—	(4)	—	—	(4)	—	—	—
Deferred tax expense (benefit):
Federal	9	22	70	73	30	26	(75)	(9)	31
State	15	8	42	—	(2)	31	11	10	6
Production tax credits	(101)	(95)	(55)	(87)	(80)	(42)	(14)	(15)	(13)
Investment tax credits	(1)	(1)	(1)	—	—	—	(1)	(1)	—
	($74)	($57)	$69	($36)	($47)	$24	($51)	($19)	$49

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
	2021		2020		2019		2021		2020		2019		2021		2020		2019
Statutory federal income tax rate	21	%	21	%	21	%	21	%	21	%	21	%	21	%	21	%	21	%
State income taxes, net of federal benefits	2		2		7		(1)		(1)		8		6		6		6
Amortization of excess deferred taxes (Refer to Note 2)	(18)		(13)		(1)		(4)		(5)		—		(43)		(26)		(2)
Production tax credits	(17)		(17)		(9)		(27)		(28)		(13)		(6)		(7)		(5)
Effect of rate-making on property-related differences	(1)		(3)		(6)		(2)		(4)		(10)		(1)		(2)		(3)
Adjustment for prior period taxes	1		1		1		2		1		3		—		—		—
IPL’s tax benefit riders	—		—		(1)		—		—		(1)		—		—		—
Other items, net	—		(1)		(1)		—		—		—		(1)		—		—
Overall income tax rate	(12	%)	(10	%)	11	%	(11	%)	(16	%)	8	%	(24	%)	(8	%)	17	%

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
	2021	2020	2021	2020	2021	2020
Deferred tax liabilities:
Property	$2,389	$2,232	$1,416	$1,312	$913	$854
ATC Holdings	123	116	—	—	—	—
Other	111	101	76	83	50	41
Total deferred tax liabilities	2,623	2,449	1,492	1,395	963	895
Deferred tax assets:
Federal credit carryforwards	560	454	345	258	192	175
Net operating losses carryforwards - federal	39	77	36	71	—	1
Net operating losses carryforwards - state	38	37	3	1	—	—
Other	65	73	25	30	18	18
Subtotal deferred tax assets	702	641	409	360	210	194
Valuation allowances	(6)	(6)	—	—	—	(1)
Total deferred tax assets	696	635	409	360	210	193
Total deferred tax liabilities, net	$1,927	$1,814	$1,083	$1,035	$753	$702

Summary Of Tax Credit Carryforwards

At December 31, 2021, carryforwards and expiration dates were estimated as follows (in millions):

	Range of Expiration Dates	Alliant Energy	IPL	WPL
Federal net operating losses	2037	$186	$172	$1
State net operating losses	2022-2041	619	28	2
Federal tax credits	2022-2041	560	345	192

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)	2018	-	2020
Consolidated Iowa income tax returns (b)	2018	-	2020
Wisconsin combined tax returns (c)	2017	-	2020

(a)The 2018 and 2019 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
	2021	2020	2019	2021	2020	2019	2021	2020	2019
Current tax expense (benefit):
Federal	$1	$1	($7)	($21)	$6	($11)	$22	($11)	$12
State	3	8	24	(1)	(1)	24	6	7	13
IPL’s tax benefit riders	—	—	(4)	—	—	(4)	—	—	—
Deferred tax expense (benefit):
Federal	9	22	70	73	30	26	(75)	(9)	31
State	15	8	42	—	(2)	31	11	10	6
Production tax credits	(101)	(95)	(55)	(87)	(80)	(42)	(14)	(15)	(13)
Investment tax credits	(1)	(1)	(1)	—	—	—	(1)	(1)	—
	($74)	($57)	$69	($36)	($47)	$24	($51)	($19)	$49

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
	2021		2020		2019		2021		2020		2019		2021		2020		2019
Statutory federal income tax rate	21	%	21	%	21	%	21	%	21	%	21	%	21	%	21	%	21	%
State income taxes, net of federal benefits	2		2		7		(1)		(1)		8		6		6		6
Amortization of excess deferred taxes (Refer to Note 2)	(18)		(13)		(1)		(4)		(5)		—		(43)		(26)		(2)
Production tax credits	(17)		(17)		(9)		(27)		(28)		(13)		(6)		(7)		(5)
Effect of rate-making on property-related differences	(1)		(3)		(6)		(2)		(4)		(10)		(1)		(2)		(3)
Adjustment for prior period taxes	1		1		1		2		1		3		—		—		—
IPL’s tax benefit riders	—		—		(1)		—		—		(1)		—		—		—
Other items, net	—		(1)		(1)		—		—		—		(1)		—		—
Overall income tax rate	(12	%)	(10	%)	11	%	(11	%)	(16	%)	8	%	(24	%)	(8	%)	17	%

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
	2021	2020	2021	2020	2021	2020
Deferred tax liabilities:
Property	$2,389	$2,232	$1,416	$1,312	$913	$854
ATC Holdings	123	116	—	—	—	—
Other	111	101	76	83	50	41
Total deferred tax liabilities	2,623	2,449	1,492	1,395	963	895
Deferred tax assets:
Federal credit carryforwards	560	454	345	258	192	175
Net operating losses carryforwards - federal	39	77	36	71	—	1
Net operating losses carryforwards - state	38	37	3	1	—	—
Other	65	73	25	30	18	18
Subtotal deferred tax assets	702	641	409	360	210	194
Valuation allowances	(6)	(6)	—	—	—	(1)
Total deferred tax assets	696	635	409	360	210	193
Total deferred tax liabilities, net	$1,927	$1,814	$1,083	$1,035	$753	$702

Summary Of Tax Credit Carryforwards

At December 31, 2021, carryforwards and expiration dates were estimated as follows (in millions):

	Range of Expiration Dates	Alliant Energy	IPL	WPL
Federal net operating losses	2037	$186	$172	$1
State net operating losses	2022-2041	619	28	2
Federal tax credits	2022-2041	560	345	192

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)	2018	-	2020
Consolidated Iowa income tax returns (b)	2018	-	2020
Wisconsin combined tax returns (c)	2017	-	2020

(a)The 2018 and 2019 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
	2021	2020	2019	2021	2020	2019	2021	2020	2019
Current tax expense (benefit):
Federal	$1	$1	($7)	($21)	$6	($11)	$22	($11)	$12
State	3	8	24	(1)	(1)	24	6	7	13
IPL’s tax benefit riders	—	—	(4)	—	—	(4)	—	—	—
Deferred tax expense (benefit):
Federal	9	22	70	73	30	26	(75)	(9)	31
State	15	8	42	—	(2)	31	11	10	6
Production tax credits	(101)	(95)	(55)	(87)	(80)	(42)	(14)	(15)	(13)
Investment tax credits	(1)	(1)	(1)	—	—	—	(1)	(1)	—
	($74)	($57)	$69	($36)	($47)	$24	($51)	($19)	$49

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
	2021		2020		2019		2021		2020		2019		2021		2020		2019
Statutory federal income tax rate	21	%	21	%	21	%	21	%	21	%	21	%	21	%	21	%	21	%
State income taxes, net of federal benefits	2		2		7		(1)		(1)		8		6		6		6
Amortization of excess deferred taxes (Refer to Note 2)	(18)		(13)		(1)		(4)		(5)		—		(43)		(26)		(2)
Production tax credits	(17)		(17)		(9)		(27)		(28)		(13)		(6)		(7)		(5)
Effect of rate-making on property-related differences	(1)		(3)		(6)		(2)		(4)		(10)		(1)		(2)		(3)
Adjustment for prior period taxes	1		1		1		2		1		3		—		—		—
IPL’s tax benefit riders	—		—		(1)		—		—		(1)		—		—		—
Other items, net	—		(1)		(1)		—		—		—		(1)		—		—
Overall income tax rate	(12	%)	(10	%)	11	%	(11	%)	(16	%)	8	%	(24	%)	(8	%)	17	%

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
	2021	2020	2021	2020	2021	2020
Deferred tax liabilities:
Property	$2,389	$2,232	$1,416	$1,312	$913	$854
ATC Holdings	123	116	—	—	—	—
Other	111	101	76	83	50	41
Total deferred tax liabilities	2,623	2,449	1,492	1,395	963	895
Deferred tax assets:
Federal credit carryforwards	560	454	345	258	192	175
Net operating losses carryforwards - federal	39	77	36	71	—	1
Net operating losses carryforwards - state	38	37	3	1	—	—
Other	65	73	25	30	18	18
Subtotal deferred tax assets	702	641	409	360	210	194
Valuation allowances	(6)	(6)	—	—	—	(1)
Total deferred tax assets	696	635	409	360	210	193
Total deferred tax liabilities, net	$1,927	$1,814	$1,083	$1,035	$753	$702

Summary Of Tax Credit Carryforwards

At December 31, 2021, carryforwards and expiration dates were estimated as follows (in millions):

	Range of Expiration Dates	Alliant Energy	IPL	WPL
Federal net operating losses	2037	$186	$172	$1
State net operating losses	2022-2041	619	28	2
Federal tax credits	2022-2041	560	345	192

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)	2018	-	2020
Consolidated Iowa income tax returns (b)	2018	-	2020
Wisconsin combined tax returns (c)	2017	-	2020

(a)The 2018 and 2019 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.