Any member for whom the payment of his accumulated contributions as herein provided reduces the balance of his account in the annuity savings fund to zero and cancels his entire period of creditable service shall no longer be a member of this Retirement System.
In the case of any member who retains his membership in this Retirement System after the payment hereinabove provided and who subsequently becomes eligible for retirement benefits under this Retirement System or whose death results in benefit payments to another beneficiary, the average final compensation used in the computation of the amount of any such benefits shall be computed as of the date of commencement of his membership in the other system on the same basis as if his retirement or death had occurred as of such date of commencement. Moreover, for the sole purpose of increasing his creditable service hereunder in order to meet any applicable service requirements for benefits hereunder, any such member shall be granted membership service credits under this Retirement System on account of (i) the period of membership service cancelled under the first paragraph of this subsection and (ii) the period of his membership in the other system so long as he remains a member hereunder and, if he is a member in service under the other system, he shall be deemed to be a member in service under this Retirement System if so required for any benefit hereunder.
N.C. Gen. Stat. § 135-28.1