Mont. Code Ann. § 40-4-207

The court may order the person obligated to pay support or maintenance to make an assignment of a part of the person's periodic earnings or trust income to the person entitled to receive the payments. The assignment is binding on the employer, trustee, or other payor of the funds 2 weeks after service upon the payor of notice that the assignment has been made. The payor shall withhold from the earnings or trust income payable to the person obligated to support the amount specified in the assignment and shall transmit the payments to the person specified in the order. The payor may deduct from each payment a sum not exceeding $1 as reimbursement for costs. An employer may not discharge or otherwise discipline an employee as a result of a wage or salary assignment authorized by this section.