N.D. Cent. Code § 26.1-12-18
A mutual insurance company, other than a mutual life insurance company, shall charge and collect the full mutual premium upon its policies in cash or in the form of a note. It may fix in its bylaws the contingent mutual liability of its members for the payment of losses and expenses not provided for by the cash funds of the company, but the contingent liability of a member, if any, may not be less than a sum equal, and in addition to, the cash premium written in the policy. The total amount of the liability of a policyholder must be stated clearly and legibly upon the face of each policy. A policy may not be issued for a cash premium without an additional contingent premium unless the company has a surplus which is not less in amount than the surplus required of domestic stock insurance companies transacting the same kinds of insurance.
N.D.C.C. § 26.1-12-18