Summary of Significant Accounting Policies - Energy Prepayment Obligations and Discounts on Sales (Details) - USD ($) $ in Millions	Sep. 30, 2025	Sep. 30, 2024
Energy Prepayment Obligations and Discounts on Sales
Accounts Receivable, Allowance for Credit Loss, Current	$ 14	$ 1	[1]

[1] determine the allowance for trade receivables, TVA considers historical experience and other currently available information, including events such as customer bankruptcy and/or a customer failing to fulfill payment arrangements by the due date, among other considerations. See Note 1 — Summary of Significant Accounting Policies — Allowance for Uncollectible Accounts. At September 30, 2025, the allowance for uncollectible accounts included $14 million related to one LPC customer. (2) The allowance for uncollectible accounts was less than $1 million at September 30, 2024. In addition, the Inflation Reduction Act of 2022 ("IRA") makes credits available to certain tax-exempt entities, including TVA. Obtaining this funding requires TVA to meet certain requirements, to submit informational returns to the Internal Revenue Service ("IRS"), and to retain adequate books and records to support its filings. TVA records the credit when there is reasonable assurance that the credit will be received, and TVA complies with all conditions attached to the eligibility of the credit. The credit is recognized as a reduction of the asset and/or expense based on what the credits are intended to reimburse. At September 30, 2025, TVA recorded $72 million in Accounts receivable, net, which is classified as Other receivables above, related to these tax credits; $51 million was recorded as a reduction of Net completed plant; $19 million was recorded to reduce Operating and maintenance expense; and $2 million related to interest was recorded to Other income, net. There were no tax credits recorded in 2024. TVA received $26 million in October 2025 related to these credits.