Iowa Code § 515.16
The maximum premium payable by any member of a mutual company shall be expressed in the policy and in the application for the insurance. Such maximum may be a cash premium and an additional contingent premium not less than the cash premium, or may be solely a cash premium, which premium may be made payable in installments or regular assessments. No policy shall 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 capital stock required, at the time of the organization of such mutual insurance company, of domestic stock insurance companies writing the same kind of insurance; but said surplus shall not be less than one hundred thousand dollars.
Iowa Code § 515.16