(1) An inactive vested member may purchase any service for which the member is eligible any time prior to retirement.

(2) The inactive vested member's most recent termination date will be considered the purchase request date for all service purchases other than refunded service, which is addressed in 19-2-603, MCA and PERS retroactive service, which is addressed in 19-3-505, MCA.

(a) The actuarial cost of the service purchase will be determined based on the member's age at the time of the purchase and the member's salary at the time of the member's most recent termination.

(b) Interest, equaling the actuarially assumed rate of return for the trust fund in effect on the member's most recent termination date, will be charged and compounded annually until the member completes payment for the cost of the purchase.

(3) An inactive vested member who purchases service may not elect a retirement date prior to the date the service purchase is completed.