Mont. Code Ann. § 33-23-401

An insurer may not cancel or refuse to renew any policy insuring private residences, including but not limited to fire, home owner, theft, or liability insurance on any home occupied by the insured as a domicile, without first giving to the insured 45 days' notice in writing, including in the notice a statement of the specific reason or reasons for canceling or not renewing the policy, except that a policy may be canceled for nonpayment of premiums, in which case, the notice to the insured may not be less than 20 days.