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Note 1 - Summary of Significant Accounting Policies - Activity in the Allowance for Credit Losses (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Sep. 30, 2023 | Sep. 30, 2022 | Sep. 30, 2021
Allowance at beginning of year | $ 31.9 | $ 30.3 | $ 24.9
Provision for expected credit losses | 16.6 | 11.6 | 14.7
Write-offs, net of recoveries | (16.0) | (10.0) | (9.3)
Allowance at end of year | 32.5 | 31.9 | 30.3
Spire Missouri [Member] |  |  |
Allowance at beginning of year | 24.9 | 22.6 | 18.1
Provision for expected credit losses | 13.3 | 11.2 | 11.1
Write-offs, net of recoveries | (12.0) | (8.9) | (6.6)
Allowance at end of year | 26.2 | 24.9 | 22.6
Spire Alabama Inc [Member] |  |  |
Allowance at beginning of year | 6.3 | 6.6 | 5.5
Provision for expected credit losses | 2.6 | 0.3 | 3.1
Write-offs, net of recoveries | (3.2) | (0.6) | (2.0)
Allowance at end of year | $ 5.7 | $ 6.3 | $ 6.6

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