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Note 12 - Income Taxes (Details Textual) - USD ($) $ in Thousands | 12 Months Ended |
--- | --- | ---
Sep. 30, 2023 | Sep. 30, 2022 | Sep. 30, 2021 | Sep. 30, 2020
Unrecognized Tax Benefits that Would Impact Effective Tax Rate | $ 5,900 | $ 4,000 |  |
Unrecognized Tax Benefits, Interest on Income Taxes Accrued | 0 | 0 |  |
Spire Missouri [Member] |  |  |  |
Regulatory Order, Excess Deferred Income Tax Returned to Customers | 10,000 | 9,900 | $ 8,400 |
Unrecognized Tax Benefits that Would Impact Effective Tax Rate | 5,100 | 3,700 |  |
Unrecognized Tax Benefits | 22,900 | 19,300 | 16,100 | $ 13,000
Spire Gulf [Member] |  |  |  |
Regulatory Order, Excess Deferred Income Tax Returned to Customers | 3,100 |  |  |
Spire Mississippi [Member] |  |  |  |
Regulatory Order, Excess Deferred Income Tax Returned to Customers | 100 |  |  |
Spire Alabama Inc [Member] |  |  |  |
Regulatory Order, Excess Deferred Income Tax Returned to Customers | 200 |  |  |
Unrecognized Tax Benefits that Would Impact Effective Tax Rate | 300 | 0 |  |
Unrecognized Tax Benefits | $ 300 | $ 0 | $ 0 | $ 0

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