Mont. Code Ann. § 40-5-811

In the case of an actual or threatened adverse action that would reduce or terminate plan benefits because of nonpayment of premium or insufficient payment of premium, the other parent, the department, or the third-party custodian may advance the cost of necessary premiums and keep benefits continually in force for the child. The advance may be entered as a judgment for unpaid child support in favor of the advancing party and against the obligated parent.