Mont. Code § 85-6-101
Whenever any water users' association, having a contract with the United States government for construction of works and delivery of water and also a contract with its shareholders, organized under and by virtue of the corporation laws of this state and in conformity with the laws of the United States, shall have levied an assessment or assessments upon its capital stock, which assessment or assessments or any part thereof remain uncollected, such association shall have the power to discharge all assessments theretofore levied and to levy in lieu thereof an assessment which shall include all previous assessments levied upon the shareholders of said association and to give credit for all payments on assessments theretofore made.
§ 85-6-101, MCA