N.C. Gen. Stat. § 58-86-35
Those firefighters who are eligible pursuant to G.S. 58-86-25 may apply to the board for membership. Each firefighter upon becoming a member of the fund shall pay the director of the fund the sum of fifteen dollars ($15.00) per month; each payment shall be made no later than March 31 subsequent to the end of the calendar year in which the month occurred. The Pension Fund shall not award fully credited service based on payments received later than March 31 subsequent to the end of the calendar year in which the month occurred unless the payment is applied as provided in G.S. 58-86-45(a1). The monthly payments shall be credited to the separate account of the member and shall be kept by the custodian so it is available for payment on withdrawal from membership or retirement.
A member may elect to terminate membership in the fund at any time and request the refund of payments previously made to the fund. However, a member's delinquency in making the monthly payments required by this section does not result in the termination of membership without such an election by the member.
N.C. Gen. Stat. § 58-86-35