Mont. Code Ann. § 71-3-703

A person, company, association, or corporation entitled to a lien under 71-3-701 shall, within 90 days after the seed or grain is furnished or the funds, means, or money is advanced for the seed or grain, file in the office of the secretary of state a statement of agricultural lien as provided in 71-3-125. Unless the person entitled to a lien files the lien statement within the time required, the person is considered to have waived the right to a lien.