Mont. Code § 7-3-4433
A warrant for the payment of any claim may not be issued unless the claim is evidenced by a voucher approved by the head of the department for which the indebtedness was incurred and countersigned by the city manager. Before issuing a voucher, the supplies and materials delivered or work done must be inspected and certified to by the head of the proper department or office or by a person designated by the head of the department or office. The head of each department or office shall require proper time reports for all services rendered, to be certified by those having knowledge of the services, to serve as a basis for the preparation of payroll vouchers. Each director of a department and the director's surety are liable to the municipality for all loss or damage sustained by the municipality, by reason of the negligent or corrupt approval of any claim against the municipality in the director's department. Prior to the drawing of a warrant for the payment of any voucher or claim, the director of finance may cause an investigation or inspection to be made by a person designated by the director of finance and may summon persons and examine them under oath or affirmation, which oath or affirmation the director of finance may administer.
§ 7-3-4433, MCA