5 CFR § 831.2011 - Effect of part 772 of this chapter on CSRS lump-sum payments.
(a) An interim appointment under § 772.102 of this chapter does not affect the lump-sum payment of retirement contributions made to a separated employee unless it becomes effective within 31 days of the employee's separation from the service. An interim appointment effective within 31 days of the employee's separation makes the employee ineligible for the lump-sum payment. Payments made in error will be collected under subpart M of part 831 of this chapter.
(b) When an employee's separation is cancelled after the MSPB initial decision becomes final, when the Board issues a final order cancelling the employee's separation, or when the agency and the employee agree to cancel the separation, the agency must notify OPM and request the amount of the erroneous lump-sum payment.
(c) At the time the employee's separation is cancelled, the agency must deduct the amount of the lump-sum payment from any back pay to which the employee is entitled as required by 5 CFR 550.805(e).
(d) Amounts recovered from back pay will not be subject to waiver consideration under 5 U.S.C. 8346(b). If there is no back pay or the back pay is insufficient to recover the erroneous payment, the employee may request that OPM waive the recovery of the uncollected portion of the overpayment. If waiver is not granted, the employee must repay the erroneous payment.