California Code, Education Code - EDC § 22826

(a) A member, other than a retired member, may request to purchase up to five years of nonqualified service credit provided the member is vested in the Defined Benefit Program as provided in Section 22156.

(b) A member who requests to purchase nonqualified service credit as provided in this chapter shall contribute to the retirement fund the actuarial cost of the service, including interest as appropriate, as determined by the board based on the most recent valuation of the plan with respect to the Defined Benefit Program in effect on the date of the request, in accordance with subdivisions (a), (f), (g), and (h) of Section 22801.

(c) This section shall apply only to an application to purchase nonqualified service credit on a properly executed form provided by the system and received at the system's headquarters office prior to January 1, 2013, that is subsequently approved by the system.