Mont. Code Ann. § 13-37-123

Within 120 days after the date of each election, the commissioner shall examine and compare each statement or report filed with the commissioner pursuant to the provisions of this chapter to determine whether the statement or report conforms to the provisions of the law. The examination shall include a comparison of all reports and statements received by the commissioner pursuant to the requirements of this chapter. The commissioner may investigate the source and authenticity of any contribution or expenditure listed in any report or statement filed pursuant to this chapter or the alleged failure to report any contribution or expenditure required to be reported pursuant to this chapter.