(1) Subject to 19-9-406, a member with at least 5 years of membership service may, at any time before retirement, file a written application with the board to purchase 1 year of additional service credit for each 5 years of membership service.
(2) To purchase service credit under this section, a member shall pay the actuarial cost of the service, based on the system's most recent actuarial valuation as determined by the board.
(3) 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.