Mont. Code § 39-71-2336
The state fund shall prescribe the procedure by which an employer may elect to be bound by compensation plan No. 3, the effective time of the election, and the manner in which the election is terminated for reasons other than default in payment of premiums. Every employer electing to be bound by compensation plan No. 3 must receive from the state fund a contract or policy of insurance in a form approved by the department. All Montana operations of an employer, as defined in 39-71-117, covered by compensation plan No. 3 must be insured by the state compensation insurance fund. The premium must be paid by the employer to the state fund at times that the state fund prescribes and must be paid over by the state fund to the state treasurer to the credit of the state fund.
§ 39-71-2336, MCA