Section 847.413 - Effective date of an election(a) An election under § 847.411 is effective on the first day of NAFI employment subject to retirement coverage following CSRS- or FERS-covered employment.(b) Deductions and contributions for CSRS or FERS coverage under § 831.111 or § 841.501 of this chapter begin effective on the first day of the next pay period after the agency receives the employee's election under § 847.411(a) .(c) An election under § 847.411 is irrevocable when received by the employing agency.(d) NAFI service performed on and after the effective date of an election under § 847.411 becomes fully creditable for retirement eligibility and computation of the annuity benefit, including computation of average pay.