The provisions of 15-31-551 through 15-31-553 shall apply to all returns on file and all returns to be filed hereafter.
Mont. Code Ann. § 15-31-554, under Administration and Collection.
Mont. Code Ann. § 15-31-554
The provisions of 15-31-551 through 15-31-553 shall apply to all returns on file and all returns to be filed hereafter.