Mont. Code § 7-6-1102
A local government may issue and sell gross proceeds obligations or short-term obligations as provided in this part in anticipation of taxes or revenues budgeted to be received and appropriated for expenditure during the fiscal year in which the obligations are issued. The proceeds of the obligations may be expended solely for the purposes for which the taxes or revenues were appropriated and for costs and expenses incident to the issuance and sale. Pending expenditure, the proceeds may be invested as provided by law. The principal and interest on short-term obligations must be repaid from the money derived from the taxes and revenues in anticipation of which they were issued, income from investment of the proceeds of the obligations, and any money otherwise legally available for this purpose.
§ 7-6-1102, MCA