Mont. Code § 7-5-4306
When the amount to be paid under an installment purchase contract exceeds $4,000, the council may provide for the payment of the amount in installments extending over a period of not more than 10 years if at the time of entering into the contract, there is an unexpended balance of appropriation in the budget for the then-current fiscal year available and sufficient to pay for the portion of the contract price payable during the then-current fiscal year. The budget for each following year in which any portion of the purchase price is to be paid must contain an appropriation for the purpose of paying that portion. The limitations contained in this section do not apply to installment purchase contracts entered into pursuant to 7-7-4104.
§ 7-5-4306, MCA