(1) At any time before retirement, a member may file a written application with the board to purchase additional service credit for the purpose of calculating the member's retirement benefit. Except as provided in subsection (3), the member may purchase 1 year of additional service credit for every 5 years of membership service that the member has in the retirement system.
(2) For each year of service credit purchased under this section, a member shall contribute to the pension trust fund an amount equal to the actuarial cost of granting the service, based on the most recent actuarial valuation of the system as determined by the board.
(3) A member may not purchase more than 5 years of service credit under 19-2-707 and this section.
(4) Service credit purchased under this section is not membership service and may not be used to qualify a member for retirement or in the calculation of an actuarial reduction in benefits for a member who is not eligible for service retirement.