5 CFR §839.304

1. (a)If your error has not previously been corrected, the 6-month time limit on making an election of retirement coverage under the FERCCA (see § 839.611(a)) does not begin to run until you are notified of the error.
2. (b)If your error was previously corrected, the 18-month time limit on making an election of retirement coverage ends on September 19, 2002. Employers and OPM may extend the time limit if you were prevented from making a timely election due to a cause beyond your control (see § 839.612).