Mont. Code Ann. § 33-2-707

The state of Montana hereby preempts the field of imposing excise, privilege, franchise, income, license, and similar taxes, licenses, and fees upon insurers and their general insurance producers and insurance producers as such and on the intangible property of insurers or such insurance producers. No county, city, municipality, district, school district, or other political subdivision or agency in Montana shall levy upon insurers, or upon their general insurance producers and insurance producers as such, any such tax, license, or fee additional to such as are levied by the legislature of Montana in this code.