Mont. Code Ann. § 71-3-402
71-3-402 How lien obtained
71-3-402 . How lien obtained. In order to acquire a lien, as specified in 71-3-401 , the person performing services shall, within 30 days after the services are fully performed, file in the office of the secretary of state a statement of agricultural lien, as provided in 71-3-125 , and the address to which notice must be directed as required by 71-3-404 .