Mont. Code Ann. § 33-23-312
Cancellation or nonrenewal of all policies
33-23-312 . Cancellation or nonrenewal of all policies. Any insurer insuring a person described in 33-23-302 who elects to cancel or not renew all policies for all persons identified in 33-23-302 shall provide notice of the decision to cancel or not renew coverage to all affected persons described in 33-23-302 at least 120 days prior to cancellation or nonrenewal.