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Related Parties | 9 Months Ended
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Sep. 30, 2025
Related Party Transactions [Line Items] |
Related Parties | RELATED PARTIES Service Agreements - Pursuant to service agreements, IPL and WPL receive various administrative and general services from an affiliate, Corporate Services. These services are billed to IPL and WPL at cost based on expenses incurred by Corporate Services for the benefit of IPL and WPL, respectively. These costs consisted primarily of employee compensation and benefits, fees associated with various professional services, depreciation and amortization of property, plant and equipment, and a return on net assets. Corporate Services also acts as agent on behalf of IPL and WPL pursuant to the service agreements. As agent, Corporate Services enters into energy, capacity, ancillary services, and transmission sale and purchase transactions within MISO. Corporate Services assigns such sales and purchases among IPL and WPL based on statements received from MISO. The amounts billed for services provided, sales credited and purchases for the three and nine months ended September 30 were as follows (in millions):
| IPL |  | WPL
| Three Months |  | Nine Months |  | Three Months |  | Nine Months
| 2025 |  | 2024 |  | 2025 |  | 2024 |  | 2025 |  | 2024 |  | 2025 |  | 2024
Corporate Services billings | $50 |  | $42 |  | $147 |  | $134 |  | $49 |  | $38 |  | $144 |  | $124
Sales credited | 16 |  | — |  | 18 |  | — |  | 44 |  | 29 |  | 106 |  | 66
Purchases billed | 124 |  | 130 |  | 323 |  | 332 |  | 15 |  | 18 |  | 51 |  | 41
Net intercompany payables to Corporate Services were as follows (in millions):
| IPL |  | WPL
| September 30, 2025 |  | December 31, 2024 |  | September 30, 2025 |  | December 31, 2024
Net payables to Corporate Services | $142 |  | $135 |  | $71 |  | $64
ATC - Pursuant to various agreements, WPL receives a range of transmission services from ATC. WPL provides operation, maintenance, and construction services to ATC. WPL and ATC also bill each other for use of shared facilities owned by each party. The related amounts billed between the parties for the three and nine months ended September 30 were as follows (in millions):
| Three Months |  | Nine Months
| 2025 |  | 2024 |  | 2025 |  | 2024
ATC billings to WPL | $38 |  | $39 |  | $114 |  | $115
WPL billings to ATC | 9 |  | 5 |  | 20 |  | 12
WPL owed ATC net amounts of $10 million as of September 30, 2025 and $10 million as of December 31, 2024.
IPL [Member] |
Related Party Transactions [Line Items] |
Related Parties | RELATED PARTIES Service Agreements - Pursuant to service agreements, IPL and WPL receive various administrative and general services from an affiliate, Corporate Services. These services are billed to IPL and WPL at cost based on expenses incurred by Corporate Services for the benefit of IPL and WPL, respectively. These costs consisted primarily of employee compensation and benefits, fees associated with various professional services, depreciation and amortization of property, plant and equipment, and a return on net assets. Corporate Services also acts as agent on behalf of IPL and WPL pursuant to the service agreements. As agent, Corporate Services enters into energy, capacity, ancillary services, and transmission sale and purchase transactions within MISO. Corporate Services assigns such sales and purchases among IPL and WPL based on statements received from MISO. The amounts billed for services provided, sales credited and purchases for the three and nine months ended September 30 were as follows (in millions):
| IPL |  | WPL
| Three Months |  | Nine Months |  | Three Months |  | Nine Months
| 2025 |  | 2024 |  | 2025 |  | 2024 |  | 2025 |  | 2024 |  | 2025 |  | 2024
Corporate Services billings | $50 |  | $42 |  | $147 |  | $134 |  | $49 |  | $38 |  | $144 |  | $124
Sales credited | 16 |  | — |  | 18 |  | — |  | 44 |  | 29 |  | 106 |  | 66
Purchases billed | 124 |  | 130 |  | 323 |  | 332 |  | 15 |  | 18 |  | 51 |  | 41
Net intercompany payables to Corporate Services were as follows (in millions):
| IPL |  | WPL
| September 30, 2025 |  | December 31, 2024 |  | September 30, 2025 |  | December 31, 2024
Net payables to Corporate Services | $142 |  | $135 |  | $71 |  | $64
WPL [Member] |
Related Party Transactions [Line Items] |
Related Parties | RELATED PARTIES Service Agreements - Pursuant to service agreements, IPL and WPL receive various administrative and general services from an affiliate, Corporate Services. These services are billed to IPL and WPL at cost based on expenses incurred by Corporate Services for the benefit of IPL and WPL, respectively. These costs consisted primarily of employee compensation and benefits, fees associated with various professional services, depreciation and amortization of property, plant and equipment, and a return on net assets. Corporate Services also acts as agent on behalf of IPL and WPL pursuant to the service agreements. As agent, Corporate Services enters into energy, capacity, ancillary services, and transmission sale and purchase transactions within MISO. Corporate Services assigns such sales and purchases among IPL and WPL based on statements received from MISO. The amounts billed for services provided, sales credited and purchases for the three and nine months ended September 30 were as follows (in millions):
| IPL |  | WPL
| Three Months |  | Nine Months |  | Three Months |  | Nine Months
| 2025 |  | 2024 |  | 2025 |  | 2024 |  | 2025 |  | 2024 |  | 2025 |  | 2024
Corporate Services billings | $50 |  | $42 |  | $147 |  | $134 |  | $49 |  | $38 |  | $144 |  | $124
Sales credited | 16 |  | — |  | 18 |  | — |  | 44 |  | 29 |  | 106 |  | 66
Purchases billed | 124 |  | 130 |  | 323 |  | 332 |  | 15 |  | 18 |  | 51 |  | 41
Net intercompany payables to Corporate Services were as follows (in millions):
| IPL |  | WPL
| September 30, 2025 |  | December 31, 2024 |  | September 30, 2025 |  | December 31, 2024
Net payables to Corporate Services | $142 |  | $135 |  | $71 |  | $64
ATC - Pursuant to various agreements, WPL receives a range of transmission services from ATC. WPL provides operation, maintenance, and construction services to ATC. WPL and ATC also bill each other for use of shared facilities owned by each party. The related amounts billed between the parties for the three and nine months ended September 30 were as follows (in millions):
| Three Months |  | Nine Months
| 2025 |  | 2024 |  | 2025 |  | 2024
ATC billings to WPL | $38 |  | $39 |  | $114 |  | $115
WPL billings to ATC | 9 |  | 5 |  | 20 |  | 12
WPL owed ATC net amounts of $10 million as of September 30, 2025 and $10 million as of December 31, 2024.

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