Section 847.442 - Effective date(a) An election under § 847.441 is effective on the first day of FERS-covered employment following NAFI employment subject to retirement coverage.(b) Deductions and contributions for NAFI retirement system coverage begin effective on the first day of the next pay period after the agency receives the employee's election under § 847.441(a) .(c) An election under § 847.441 is irrevocable when received by the employing agency.