Mont. Code Ann. § 39-2-911

39-2-911 . Limitation of actions. (1) An action under this part must be filed within 1 year after the date of discharge.

(2) If an employer maintains written internal procedures, other than those specified in 39-2-912 , under which an employee may appeal a discharge within the organizational structure of the employer, the employee shall first exhaust those procedures prior to filing an action under this part. The employee's failure to initiate or exhaust available internal procedures is a defense to an action brought under this part. If the employer's internal procedures are not completed within 90 days from the date the employee initiates the internal procedures, the employee may file an action under this part and for purposes of this subsection the employer's internal procedures are considered exhausted. The limitation period in subsection (1) is tolled until the procedures are exhausted. In no case may the provisions of the employer's internal procedures extend the limitation period in subsection (1) more than 120 days.

(3) If the employer maintains written internal procedures under which an employee may appeal a discharge within the organizational structure of the employer, the employer shall within 14 days of the date of the discharge notify the discharged employee in writing or electronically of the existence of the internal procedures. The timeframe for the employee to initiate the procedures, if any, begins to run from the date the employer sends or provides a copy of the internal procedures in writing or electronically. A copy of the procedures must be considered provided to the employee if the employer sends a copy of the procedures to the employee's last-known postal mailing address or electronic mailing address or the employee's attorney. If the employer fails to comply with this subsection, the discharged employee need not comply with subsection (2).

(4) If a plaintiff commences a civil action for wrongful discharge under this part, the plaintiff shall make service of process no later than 6 months after filing the complaint. If the plaintiff fails to make service of process within the 6-month period, the court, on motion or on its own initiative, shall dismiss the action without prejudice as to a defendant unless that defendant has made an appearance in the civil action. If the plaintiff fails to make service of process within the 6-month period, the remaining 1-year period of limitations for a civil action under this part resumes regardless of whether the civil action is dismissed.