Mont. Code Ann. § 61-10-222

Prior to or at the time of registration of the vehicle as required under chapter 3 or chapter 4 or prior to the operation of the vehicle on the public highways, fees provided in this part must be paid in the full amount unless otherwise provided by law. With respect to vehicles operating on the highways with a current temporary registration permit issued under 61-3-224, the fees provided in this part are due and payable at the time of registration.