Mont. Code Ann. § 25-4-301

In pleading the statute of limitations, it is not necessary to state the facts showing the defense, but it may be stated generally that the cause of action is barred by the provisions of section.... (giving the number of the section and subsection thereof, if it is so divided, relied upon). If such allegation be controverted, the party pleading must establish, on the trial, the facts showing that the cause of action is so barred.