California Code, Government Code - GOV § 31658

(a) An active member may elect, by written notice filed with the board, to make contributions pursuant to this section and to receive up to five years of service credit in the retirement system for additional retirement credit, if the member has completed at least five years of credited service with that retirement system.

(b) As used in this section, “additional retirement credit” means time that does not otherwise qualify as county service, public service, military service, medical leave of absence, or any other time recognized for service credit by the retirement system.

(c) Notwithstanding any other provision of this chapter, service credit for additional retirement credit may not be counted to meet the minimum qualifications for service or disability retirement or for purposes of establishing eligibility for any benefits based on 30 years of service, additional ad hoc cost-of-living benefits based on service credit, health care benefits, or any other benefits based upon service credit.

(d) Any member who elects to make contributions and receive service credit for additional retirement credit shall contribute to the retirement fund, prior to the effective date of his or her retirement, by lump-sum payment or by installment payments over a period not to exceed 10 years, an amount that, at the time of commencement of purchase, in the opinion of the board and the actuary, is sufficient to not place any additional financial burden upon the retirement system.

(e) No member may receive service credit under this section for any additional retirement credit for which he or she has not completed payment pursuant to subdivision (d) before the effective date of his or her retirement. Subject to the limitations of United States Internal Revenue Service regulations, a member who has elected to make payment in installments may complete payment by lump sum at any time prior to the effective date of his or her retirement.

(f) Any sums paid by a member pursuant to this section shall be considered to be and administered as contributions by the member.

(g) This section is not operative in any county until the board of supervisors, by resolution adopted by majority vote, makes this section applicable in the county.

(h) Pursuant to Section 7522.46, this section shall apply only to an application to purchase additional retirement credit that was received by the retirement system prior to January 1, 2013, that is subsequently approved by the system.