Section 847.423 - Credit for refunded FERS service(a) An employee or survivor who elects FERS coverage with credit for NAFI service under § 847.421 will receive credit in the FERS annuity for the service represented by any refund of the unexpended balance under § 843.202 of this chapter.(b) The amount of the refund, increased by interest as computed under § 842.305(e) of this chapter, will be added to the deficiency computed under § 847.604 and collected in accordance with the provisions of § 847.609 (pertaining to a monthly reduction in the annuity benefit).