Section 847.805 - What NAFI service can employees elect to credit toward retirement eligibility under CSRS or FERS?(a) Employees may elect to credit under this subpart any NAFI service that isn't already creditable under 5 U.S.C. 8332(b)(16) , or under 5 CFR part 847, subpart D.(b) NAFI service used to qualify for an immediate annuity based on an election in paragraph (a) of this section cannot be credited in a NAFI retirement plan for any purpose including eligibility and calculations of NAFI benefits.