Mont. Code Ann. § 15-23-116 — Statute Of Limitations

15-23-116 . Statute of limitations. (1) Except as otherwise provided in this section, no deficiency may be assessed or collected with respect to the year for which a return is filed unless the notice of additional tax proposed to be assessed is mailed within 5 years from the date the return was filed. For the purposes of this section, a return filed before the last day prescribed for filing is considered as filed on the last day. If the taxpayer, before the expiration of the period prescribed for assessment of the tax, consents in writing to an assessment after that time, the tax may be assessed at any time prior to the expiration of the period agreed upon.
(2) Except as provided in subsection (3), a refund or credit may not be allowed or paid unless the taxpayer has paid the tax under protest as provided by 15-1-402 .
(3) If the department determines that the taxpayer has made an overpayment, the department shall refund or credit the overpayment if the overpayment was discovered within 5 years from the last day prescribed for filing the return.
(4) If a return is required to be filed and the taxpayer fails to file the return, the tax may be assessed or an action to collect the tax may be brought at any time. If a return is required to be filed and the taxpayer files a fraudulent return, the 5-year period provided for in subsection (1) does not begin until discovery of the fraud by the department.