Section 847.433 - Exclusion from FERS for future service(a) An employee who elects NAFI retirement system coverage with credit for FERS service under § 847.431(a) is excluded from coverage under FERS during that and all subsequent periods of employment, including any periods of service as a reemployed annuitant.(b) FERS service which becomes creditable in a NAFI retirement benefit based on an election under § 847.431 is not creditable for any purpose under FERS.