Mont. Code Ann. § 32-2-922

Interest or commissions unpaid, although due or accrued, on debts owing to any mutual association may not be included in calculation of its profits, unless the mutual association keeps its books on a complete accrual basis. A mutual association that keeps it books on a complete accrual basis shall show on its books accrued interest receivable on notes, bonds, and other investments, unless the accrued interest is past due, and shall carry on its books accrued interest, taxes, and expenses payable.