Mont. Code Ann. § 25-10-501

The party in whose favor judgment is rendered and who claims the party's costs shall deliver to the clerk and serve upon the adverse party, within 5 days after the verdict or notice of the decision of the court or referee or, if the entry of the judgment on the verdict or decision is stayed, then before the entry is made, a memorandum of the items of the party's costs and necessary disbursements in the action or proceeding. The memorandum must be verified by the oath of the party, the party's attorney or agent, or the clerk of the party's attorney, stating that to the best of the person's knowledge and belief, the items are correct and that the disbursements have been necessarily incurred in the action or proceeding.