Montana Code Annotated · § 15-68-520 — Limitations

(1) Except in the case of a person that purposely or knowingly, as those terms are defined in 45-2-101, files a false or fraudulent return violating the provisions of this chapter, a deficiency may not be assessed or collected with respect to a quarter for which a return 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 that the return was filed. For purposes of this section, a return 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 to which consent was given.