Mont. Code § 7-12-4223
During the period described in 7-12-4225(2), when any special improvement district bond or sidewalk, curb, and alley approach warrants that are secured by the revolving fund or any interest on the bond or warrants becomes due and payable and there is either no money or insufficient money in the appropriate district fund after a transfer from the appropriate district reserve account, if established, with which to pay the bond, warrant, or interest, an amount sufficient to make up the deficiency must be loaned by the revolving fund to the district fund. The bond, warrant, or interest must be paid from the money loaned or from the money loaned and money available in the district fund. The loan must be made even if, in the case of bonds or warrants bearing interest at a variable rate, the interest rate on the special assessments at the time the loan is made is less than or later becomes less than the interest rate on the bonds or warrants.
§ 7-12-4223, MCA