Montana Title 15. Taxation § 15-39-108. Limitations

(1) Except in the case of a person who purposely or knowingly, as those terms are defined in 45-2-101, files a false or fraudulent statement violating the provisions of this part, a deficiency may not be assessed or collected with respect to a tax period for which a statement is filed unless the notice of additional tax proposed to be assessed is mailed to or personally served upon the taxpayer within 5 years from the date on which the statement was filed. For purposes of this section, a statement filed before the last day prescribed for filing is considered to be filed on the last day.

(2) If, before the expiration of the 5-year period prescribed in subsection (1) for assessment of the tax, the taxpayer consents in writing to an assessment after expiration of the 5-year period, a deficiency may be assessed at any time prior to the expiration of the period consented to.