5 CFR §841.803

1. (a)An annuitant may decline to accept all or any part of the amount of his or her annuity by a waiver signed and filed with the Office of Personnel Management (OPM).
2. (b)A waiver is effective the first day of the month following the month in which it is received in OPM, unless a later effective date is specified by the annuitant.
3. (c)A waiver remains in effect until revoked or changed by the annuitant in writing, except as provided in paragraph (f) of this section. The effective date of a revocation or change will be the first day of the month following the month in which the request to revoke or change is received in OPM, unless a later date is specified by the annuitant.
4. (d)The amount of annuity that is waived is forfeited during the period the waiver is in effect and cannot be recovered.
5. (e)An annuity which has a waiver in effect will not be increased by cost-of-living adjustments (COLA) authorized under 5 U.S.C. 8462. Upon cancellation of a waiver, the rate of annuity will be increased by any COLA authorized during the period a waiver was in effect.
6. (f)Upon the death of an annuitant with a waiver in effect, any survivor annuity payable will be authorized at the full rate of annuity as though the waiver had not been in effect, unless the survivor annuitant executes a waiver.