31 C.F.R. § 29.335 – Refunded service.

(a) Periods of civilian service that were subject to retirement deductions but for which the deductions were refunded to the employee are creditable for Federal Benefit Payments if the redeposit for the service was paid in full to the District government as of June 30, 1997.
(b) No credit is allowed for Federal Benefit Payments for any period of civilian service that was subject to retirement deductions but for which the deductions were refunded to the employee if the redeposit for the service was not paid in full to the District government as of June 30, 1997.
(c) If the redeposit for the service was paid in installments, but was not paid in full as of June 30, 1997, Treasury shall transfer to the District an amount equal to the portion of the redeposit completed prior to June 30, 1997.
Calculation of the Amount of Federal Benefit Payments