DISPOSITIONS	9 Months Ended
Jun. 30, 2026
Discontinued Operations and Disposal Groups [Abstract]
DISPOSITIONS	DISPOSITIONS Sale and Disposition of Wynyard SOP Business On February 3, 2026, the Company entered into a share purchase agreement (the “Share Purchase Agreement”) to sell its SOP business in Wynyard, Saskatchewan, Canada. The Share Purchase Agreement provided for total consideration of approximately $30.8 million, prior to indebtedness and working capital adjustments totaling $2.1 million. The transaction closed on March 1, 2026. At closing, the Company received cash proceeds of $23.3 million, net of (i) $3.9 million ($5.2 million denominated in Canadian dollars (“CAD”)) placed in escrow, (ii) $1.3 million of cash on hand transferred to the buyer, and (iii) $0.2 million of transaction costs. The escrow agreement provides for potential purchase price adjustments related to indemnification of claims. Of the escrowed amount, approximately CAD $3.3 million is scheduled to be released on March 1, 2027, and the remaining CAD $1.9 million is scheduled to be released on March 1, 2028, in each case plus accrued interest and net of any amounts deducted pursuant to the terms of the escrow agreement. As a result of the transaction, the Company recorded a pre-tax Loss on sale of business, net, of $14.5 million, which included $13.1 million of cumulative foreign currency translation adjustments reclassified from Accumulated other comprehensive loss, for the nine months ended June 30, 2026. Prior to the sale, the results of the Wynyard SOP business were included in the Company’s Plant Nutrition operating segment. The transaction supports the Company’s ongoing balance sheet strengthening and debt-reduction initiatives. In connection with the transaction, the Company entered into a transition services agreement with the purchaser that is designed to facilitate the orderly transfer of the operations, including administrative services, which are generally to be provided within 12 months after the closing date. This agreement was not material and does not confer upon the Company the ability to influence the operating or financial policies of the Wynyard SOP business subsequent to March 1, 2026. As of the March 1, 2026 disposal date, the business had net assets with a carrying value of $30.2 million. Fortress Exit On March 25, 2025, the Company took measures to align the Company’s cost structure to its current business needs as part of a larger strategic refocus to improve the profitability of the Company’s core Salt and Plant Nutrition businesses. Specifically, the Company began the process of exiting the Fortress North America, LLC (“Fortress”) fire retardant business and terminating the employment of all Fortress employees. The results of operations of Fortress were included in Corporate and Other segment. Impairment. As a result of the above items impacting Fortress, the Company determined that there were indicators of impairment with the associated Fortress intangible assets. Accordingly, the Company performed an impairment assessment of its customer relationships and trade name intangible assets, and their fair value was determined to be zero using an income approach in accordance with ASC 820, Fair Value Measurement, utilizing Level 3 inputs. As a result, the Company recorded a loss on impairment of $0.0 million and $53.0 million, for the three and nine months ended June 30, 2025, respectively. Additionally, the Company performed an impairment test on the remaining Fortress asset group (including PP&E, inventory, and in-process research and development (“IPR&D”)), with a carrying amount of $19.7 million. The impairment test under ASC 360, Property, Plant, and Equipment, compared the asset group’s undiscounted cash flows to its carrying amount. The Company determined the fair value of the asset group using a market approach under ASC 820, Fair Value Measurement (Level 2 inputs). The asset group (PP&E, inventory, and IPR&D) was not impaired as its fair value, based on market indications approximated or exceeded its carrying value. The fair value estimates involved significant estimates and assumptions. On June 30, 2025, the Company performed an impairment test on the remaining Fortress asset group related to property, plant, and equipment and recorded a loss on impairment, net of $0.7 million, during both the three and nine months ended June 30, 2025. Equipment Lease. On May 20, 2025, the Company purchased equipment previously leased for Fortress of $2.8 million, resulting in the termination of the related lease. The Company derecognized the right-of-use asset and lease liability. The carrying value of the lease liability was $1.5 million and the right-of-use asset was $1.4 million at the date of purchase. The $1.3 million difference between the purchase price and the lease liability was recorded as an adjustment to the carrying amount of the purchased equipment. The remaining equipment, with a carrying value of $2.7 million at June 30, 2025, was included in Property, plant and equipment, net, in the Condensed Consolidated Balance Sheets. Contingent Consideration. In connection with the acquisition of Fortress on May 5, 2023, the Company entered into a contingent consideration arrangement for up to $28 million to be paid in cash and/or Compass Minerals common stock upon the achievement of certain performance measures over a five year period, and a cash earn-out based on volumes of certain Fortress fire retardant products sold over a 10-year period. Given the business ceased operations and had no future expected cash flows, the carrying value of the contingent consideration of $7.9 million was reduced to zero as of March 31, 2025. For the three and nine months ended June 30, 2025, the Company recorded income, included in Other operating expense (income) of $0.0 million and $7.9 million, respectively. Asset Purchase Agreement. On May 30, 2025, the Company entered into an Asset Purchase Agreement, selling substantially all Fortress assets for $20.0 million in cash. The Company paid approximately $0.4 million of costs related to the sale. The assets included in the sale had a net book value of approximately $17.2 million. The fair value of proceeds received, net of transaction costs, exceeded the carrying amount, resulting in a gain of $2.4 million, recorded in Other expense (income), net, in the Condensed Consolidated Statements of Operations for both the three and nine months ended June 30, 2025.

On February 3, 2026, the Company entered into a share purchase agreement (the “Share Purchase Agreement”) to sell its SOP business in Wynyard, Saskatchewan, Canada. The Share Purchase Agreement provided for total consideration of approximately $30.8 million, prior to indebtedness and working capital adjustments totaling $2.1 million.

The transaction closed on March 1, 2026. At closing, the Company received cash proceeds of $23.3 million, net of (i) $3.9 million ($5.2 million denominated in Canadian dollars (“CAD”)) placed in escrow, (ii) $1.3 million of cash on hand transferred to the buyer, and (iii) $0.2 million of transaction costs. The escrow agreement provides for potential purchase price adjustments related to indemnification of claims. Of the escrowed amount, approximately CAD $3.3 million is scheduled to be released on March 1, 2027, and the remaining CAD $1.9 million is scheduled to be released on March 1, 2028, in each case plus accrued interest and net of any amounts deducted pursuant to the terms of the escrow agreement.

As a result of the transaction, the Company recorded a pre-tax Loss on sale of business, net, of $14.5 million, which included $13.1 million of cumulative foreign currency translation adjustments reclassified from Accumulated other comprehensive loss, for the nine months ended June 30, 2026. Prior to the sale, the results of the Wynyard SOP business were included in the Company’s Plant Nutrition operating segment. The transaction supports the Company’s ongoing balance sheet strengthening and debt-reduction initiatives.

In connection with the transaction, the Company entered into a transition services agreement with the purchaser that is designed to facilitate the orderly transfer of the operations, including administrative services, which are generally to be provided within 12 months after the closing date. This agreement was not material and does not confer upon the Company the ability to influence the operating or financial policies of the Wynyard SOP business subsequent to March 1, 2026.

On March 25, 2025, the Company took measures to align the Company’s cost structure to its current business needs as part of a larger strategic refocus to improve the profitability of the Company’s core Salt and Plant Nutrition businesses. Specifically, the Company began the process of exiting the Fortress North America, LLC (“Fortress”) fire retardant business and terminating the employment of all Fortress employees. The results of operations of Fortress were included in Corporate and Other segment.

Impairment. As a result of the above items impacting Fortress, the Company determined that there were indicators of impairment with the associated Fortress intangible assets. Accordingly, the Company performed an impairment assessment of its customer relationships and trade name intangible assets, and their fair value was determined to be zero using an income approach in accordance with ASC 820, Fair Value Measurement, utilizing Level 3 inputs. As a result, the Company recorded a loss on impairment of $0.0 million and $53.0 million, for the three and nine months ended June 30, 2025, respectively.

Additionally, the Company performed an impairment test on the remaining Fortress asset group (including PP&E, inventory, and in-process research and development (“IPR&D”)), with a carrying amount of $19.7 million. The impairment test under ASC 360, Property, Plant, and Equipment, compared the asset group’s undiscounted cash flows to its carrying amount. The Company determined the fair value of the asset group using a market approach under ASC 820, Fair Value Measurement (Level 2 inputs). The asset group (PP&E, inventory, and IPR&D) was not impaired as its fair value, based on market indications approximated or exceeded its carrying value. The fair value estimates involved significant estimates and assumptions.

On June 30, 2025, the Company performed an impairment test on the remaining Fortress asset group related to property, plant, and equipment and recorded a loss on impairment, net of $0.7 million, during both the three and nine months ended June 30, 2025.

Equipment Lease. On May 20, 2025, the Company purchased equipment previously leased for Fortress of $2.8 million, resulting in the termination of the related lease. The Company derecognized the right-of-use asset and lease liability. The carrying value of the lease liability was $1.5 million and the right-of-use asset was $1.4 million at the date of purchase. The $1.3 million difference between the purchase price and the lease liability was recorded as an adjustment to the carrying amount of the purchased equipment. The remaining equipment, with a carrying value of $2.7 million at June 30, 2025, was included in Property, plant and equipment, net, in the Condensed Consolidated Balance Sheets.

Contingent Consideration. In connection with the acquisition of Fortress on May 5, 2023, the Company entered into a contingent consideration arrangement for up to $28 million to be paid in cash and/or Compass Minerals common stock upon the achievement of certain performance measures over a five year period, and a cash earn-out based on volumes of certain Fortress fire retardant products sold over a 10-year period. Given the business ceased operations and had no future expected cash flows, the carrying value of the contingent consideration of $7.9 million was reduced to zero as of March 31, 2025. For the three and nine months ended June 30, 2025, the Company recorded income, included in Other operating expense (income) of $0.0 million and $7.9 million, respectively.

Asset Purchase Agreement. On May 30, 2025, the Company entered into an Asset Purchase Agreement, selling substantially all Fortress assets for $20.0 million in cash. The Company paid approximately $0.4 million of costs related to the sale. The assets included in the sale had a net book value of approximately $17.2 million. The fair value of proceeds received, net of transaction costs, exceeded the carrying amount, resulting in a gain of $2.4 million, recorded in Other expense (income), net, in the Condensed Consolidated Statements of Operations for both the three and nine months ended June 30, 2025.