Mont. Code Ann. § 85-7-1955

When money is provided by the United States for liquidating bonded indebtedness of any irrigation district, the county treasurer is authorized and empowered to cancel the district bonds so liquidated and surrender them to the United States, taking therefor a receipt signed by the secretary of the interior, which receipt shall be placed in the records of the county treasurer and shall be conclusive evidence of the cancellation and surrender of the district bonds.