Mont. Code Ann. § 25-13-806

Written notice of redemption must be given to the sheriff and a duplicate filed with the county clerk, and if any taxes or assessments are paid by the redemptioner or if the redemptioner has or acquired any liens other than that upon which the redemption was made, notice must in the same manner be given to the sheriff and filed with the county clerk. If the notice is not filed, the property may be redeemed without paying the tax, assessments, or lien.