Mont. Code § 15-23-507
At the time of computing net proceeds assessments, the department shall also determine the royalty lists or schedules for each county in which the mines and mining claims are located. The department shall prepare from the net proceeds and royalty assessments a tax roll that must be furnished to the county treasurer on or before the following September 15. Upon furnishing the tax roll, the taxes are due and payable. Assessments of royalty on production of metals and minerals other than petroleum and natural gas must be entered by the department in the property tax record in the name of the recipient or owner of the royalty. The county treasurer shall give full notice of the assessment to the recipient or royalty owner and shall collect the taxes in the same manner as taxes on net proceeds of mines. Taxes on the royalty assessments and taxes on net proceeds of mines are payable at the times specified in 15-16-102, and any delinquencies in the payment are subject to the interest and penalties provided in 15-16-102.
§ 15-23-507, MCA