Section 846.704 - Irrevocability of an election of FERS coverage(a) An election to be covered by FERS becomes irrevocable on the date it becomes effective.(b) If, during the 1998 open enrollment period, an employee files an election on an SF 3109 to remain covered by CSRS, the employee may revoke such an election by filing another election during the 1998 open enrollment period.