N.D. Cent. Code § 40-46-04

Every full-time city employee who qualifies for membership in the city employees' pension fund shall, at the time of employment, pay to the treasurer of the pension fund a membership fee to be fixed by the board of trustees in an amount not exceeding twenty-five dollars. Each member shall be assessed and required to pay annually an amount not more than seven percent, to be determined by the board of trustees, upon the amount of annual salary paid to the member, and such assessment shall be deducted and retained out of such salary in equal monthly installments. No assessment shall be made after retirement.