Mont. Code Ann. § 7-12-2205

Any assessment levied and made for any purpose mentioned in this part, together with all costs and penalties, shall constitute a lien upon and against the property upon which said assessments are made and levied from and after the date of the final passage and adoption of the resolution levying the same. This lien can be only extinguished by payment of such assessments, with all penalties, costs, and interest.