Mont. Code Ann. § 15-24-1202

When such property is held under a contract of sale or other agreement whereby on certain payment or payments the legal title is or may be acquired by such person, such property shall be assessed to such person and taxed without deduction on account of the whole or any part of the purchase price or other sum due on such property remaining unpaid, provided that the lien for such tax neither attach to, impair, nor be enforced against any interest of the state of Montana or any department, agency, or subdivision thereof.