Mont. Code Ann. § 15-23-523

Every corporation which shall be dissolved or cease to do business in this state during any taxpaying year shall make all statements, reports, and returns required by law to be made with reference to the net proceeds of mines and pay the tax due for such period as it transacted business on or before the date of such dissolution or cessation of business. The department of revenue may grant a reasonable extension of time for filing a return upon good cause shown therefor.