Mont. Code Ann. § 80-7-921

In addition to the penalties set out in 80-7-922, a person who fails to pay or improperly pays any fee assessment or fee assessed under the provisions of this part is subject to a penalty of $100 or double the assessment, whichever is greater, including the original fee. The penalty must be paid to the department and deposited as provided in 80-7-908. A certification issued to a person who fails to pay or improperly pays any fee assessment or fee assessed under the provisions of this part is invalid until the original fee and penalty are paid to the department.