20 CFR §218.8

1. (a)Before annuity is awarded. A claimant may change the annuity beginning date if—
   1. (1)The claimant requests the change in a signed statement; and
   2. (2)The statement is received by the Board on or before the date of the claimant's death.
2. (b)After annuity is awarded. An award can be reopened to change the annuity beginning date to a later date if—
   1. (1)The annuitant requests the change in a signed statement;
   2. (2)The statement is received by the Board on or before the date of the annuitant's death;
   3. (3)The annuitant shows that it is to his or her advantage to have a later annuity beginning date; and
   4. (4)All payments made for the period before the later annuity beginning date are recovered by cash refund or setoff.