22 C.F.R. § 19.7-3
A spousal agreement shall also be used by a participant or former participant who has a former spouse on February 15, 1981, to elect a regular survivor annuity for such former spouse in accordance with § 19.11-2(e) . An agreement to establish or increase any benefit for a former spouse entered into while the principal is married to someone else, must be signed and agreed to by both the spouse and the former spouse. An agreement affecting pension benefits may be filed at any time and will govern payments made after its acceptance by PER/ER/RET. An agreement affecting a regular survivor annuity must be filed before the end of the 12-month period after the divorce involving that former spouse or at the time of retirement, whichever occurs first, except as authorized in § 19.11-2(b) for persons retired on February 15, 1981, or in § 19.11-2(e) with respect to persons who were former spouses on February 15, 1981. This filing requirement stated in the Act makes it impossible to adjust, other than by court order, a regular survivor annuity for a former spouse when the divorce occurs after a retirement which occurs on or after February 15, 1981. The survivor annuity for the former spouse in such case is fixed by any spousal agreement entered into prior to the divorce, by § 19.11-2 or by court order. An agreement affecting supplemental survivor benefits or lump-sum payments must be filed before the supplemental annuity of the principal begins or lump-sum payment is made.
22 C.F.R. §19.7-3