Mont. Code § 85-7-2155
When lands and premises with attached tax liens and upon and against which the certificates have been issued for the taxes and assessments of the irrigation district are not redeemed within the time provided for by 15-18-111, the board of county commissioners of the county, within 3 months thereafter, shall cause these lands and premises to be sold as provided for by law, and out of the proceeds of the sale, the county treasurer of the county shall pay to the holder or holders of the certificates the sum for which the same were issued, with interest as provided for to the date of the sale of the lands by the board of county commissioners, and no lands and premises so held by any county and against which the certificates provided for by this chapter have been issued may, upon such sale, be struck off or sold for a less sum than the amount of taxes and assessments of the irrigation district represented by the certificate, inclusive of the interest thereon, in addition to the state and county taxes, if any, against the same.
§ 85-7-2155, MCA