Mont. Code Ann. § 7-12-4604

At any time within 15 days after the date of the first publication or posting of the notice of passage of the resolution of intention, an owner of property who would be liable for district assessments may make a written protest against the proposed improvement or the creation of the district, or both. The protest must be delivered, in writing, to the clerk of the city council, who shall endorse on the protest the date of receipt.