Mont. Code Ann. § 7-12-4332

It shall be the duty of the city or town council to estimate, as nearly as practicable, the cost of maintaining such lights and furnishing electrical current therefor each year and the portion thereof to be assessed against the property embraced within the district and, before the first Monday in October, to pass and finally adopt a resolution levying and assessing said property within said district with an amount equal to the proportion of the cost of such maintenance and electrical current so determined to be especially assessed against said property.