20 CFR § 261.4 - Decisions which shall not be reopened.
The following decisions shall not be reopened:
(a) An award of an annuity beginning date to an applicant later found to have been in compensated service to an employer under part 202 of this chapter on that annuity beginning date and who is found not to be at fault in causing the erroneous award; provided, however, that this exception shall not operate to permit payment of benefits for any month in which the claimant is found to be engaged in compensated service.
(2) The erroneously credited months of service do not exceed six months; and
(3) The annuitant is found not to be at fault in causing the erroneous crediting.
(c) An erroneous award of an annuity where the error is no greater than one dollar per month per annuity affected.
(d) An erroneous award of a lump sum or accrued annuity payment where the error is no greater than $25.00.