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Related Parties (Tables) | 9 Months Ended
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Sep. 30, 2025
Related Party Transactions [Line Items] |
Services Provided, Sales Credited And Purchases | 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 | 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
Related Amounts Billed Between Parties | 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
IPL [Member] |
Related Party Transactions [Line Items] |
Services Provided, Sales Credited And Purchases | 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 | 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] |
Services Provided, Sales Credited And Purchases | 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 | 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
Related Amounts Billed Between Parties | 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

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