Subsequent Events	6 Months Ended
Mar. 31, 2026
Subsequent Events [Abstract]
Subsequent Events	14. SUBSEQUENT EVENTS The Company has evaluated subsequent events through May 6, 2026, the date on which these condensed consolidated financial statements were issued. Completion of Sale of Spire Marketing On April 30, 2026, the Company completed the previously announced sale of all of the issued and outstanding membership interests of Spire Marketing to Boardwalk for $212.0 in cash, subject to customary post-closing adjustments. The closing followed the satisfaction of all material closing conditions, including the conversion of Spire Marketing from a Missouri corporation to a Delaware limited liability company and compliance with applicable regulatory approvals. The proceeds from the sale were used to partially repay borrowings incurred in connection with the Piedmont Tennessee Transaction and for general corporate purposes. See Note 3 - Divestitures for additional information regarding the classification of Spire Marketing as a discontinued operation. Agreement to Sell Spire Storage On April 14, 2026, Spire Midstream LLC, a wholly-owned subsidiary of Spire, entered into a Membership Interest Purchase Agreement with Subterra Energy Holdings, LLC, an affiliate of I Squared Capital, for the sale of all of the issued and outstanding membership interests of Belle Butte LLC. Belle Butte LLC owns all of the outstanding membership interests in Spire Storage West LLC and Spire Storage Salt Plains LLC. Total consideration for the transaction is approximately $650.0, consisting of $600.0 payable in cash at closing and a $50.0 fixed deferred payment expected to be received in fiscal 2027. The transaction is subject to customary closing conditions, including clearance under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended, and other regulatory approvals, and is expected to close during the second half of fiscal year 2026. See Note 3 - Divestitures for additional information regarding the classification of Spire Storage as a discontinued operation. Agreement to Sell Spire Mississippi On April 21, 2026, Spire EnergySouth Inc., a wholly-owned subsidiary of Spire, entered into a Stock Purchase Agreement with Delta Mississippi Gas Company, LLC, for the sale of all of the issued and outstanding shares of Spire Mississippi Inc. for a cash purchase price of $75.0, subject to customary purchase price adjustments. Closing is expected in the first quarter of fiscal year 2027, subject to the regulatory approval of the Mississippi Public Service Commission and other customary closing conditions. Upon certain qualifying terminations, the purchaser will be required to pay a reverse termination fee of $7.5. Spire Mississippi is classified as held for sale within continuing operations. See Note 3 - Divestitures for additional information.

Subsequent Events

6 Months Ended

Mar. 31, 2026

14. SUBSEQUENT EVENTS

The Company has evaluated subsequent events through May 6, 2026, the date on which these condensed consolidated financial statements were issued.

Completion of Sale of Spire Marketing

On April 30, 2026, the Company completed the previously announced sale of all of the issued and outstanding

membership interests of Spire Marketing to Boardwalk for $212.0 in cash, subject to customary post-closing adjustments. The closing followed the satisfaction of all material closing conditions, including the conversion of Spire Marketing from a Missouri corporation to a Delaware limited liability company and compliance with applicable regulatory approvals. The proceeds from the sale were used to partially repay borrowings incurred in connection with the Piedmont Tennessee Transaction and for general corporate purposes. See Note 3 - Divestitures for additional information regarding the classification of Spire Marketing as a discontinued operation.

Agreement to Sell Spire Storage

On April 14, 2026, Spire Midstream LLC, a wholly-owned subsidiary of Spire, entered into a Membership Interest Purchase Agreement with Subterra Energy Holdings, LLC, an affiliate of I Squared Capital, for the sale of all of the issued and outstanding membership interests of Belle Butte LLC. Belle Butte LLC owns all of the outstanding membership interests in Spire Storage West LLC and Spire Storage Salt Plains LLC. Total consideration for the transaction is approximately $650.0, consisting of $600.0 payable in cash at closing and a $50.0 fixed deferred payment expected to be received in fiscal 2027. The transaction is subject to customary closing conditions, including clearance under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended, and other regulatory approvals, and is expected to close during the second half of fiscal year 2026. See Note 3 - Divestitures for additional information regarding the classification of Spire Storage as a discontinued operation.

Agreement to Sell Spire Mississippi

On April 21, 2026, Spire EnergySouth Inc., a wholly-owned subsidiary of Spire, entered into a Stock Purchase Agreement with Delta Mississippi Gas Company, LLC, for the sale of all of the issued and outstanding shares of Spire Mississippi Inc. for a cash purchase price of $75.0, subject to customary purchase price adjustments. Closing is expected in the first quarter of fiscal year 2027, subject to the regulatory approval of the Mississippi Public Service Commission and other customary closing conditions. Upon certain qualifying terminations, the purchaser will be required to pay a reverse termination fee of $7.5. Spire Mississippi is classified as held for sale within continuing operations. See Note 3 - Divestitures for additional information.