5 CFR §841.203

1. (a)Except as provided in paragraphs (b) and (c) of this section, an applicant for benefits under FERS may withdraw his or her application for benefits until a payment based on that application has been authorized, but not thereafter.
2. (b)An applicant for benefits under FERS may not withdraw his or her application for benefits after OPM has received a certified copy of a court order (under part 581 of this chapter or subpart I of this part) affecting the benefits.
3. (c)When an “appropriate authority” determines that the separation upon which payment has been based is an “unjustified or unwarranted personnel action” as these terms are defined in § 550.804 of this chapter, an individual may withdraw his/her application for FERS benefits within 60 days of the decision. As provided in § 550.805, any FERS payments must be deducted from any back pay award.