5 C.F.R. § 839.1002
If you made contributions to the TSP after your qualifying retirement coverage error was previously corrected, OPM will compute the lost earnings on your make-up contributions to the TSP under the following circumstances:
| You were in: | And werepreviously corrected to: | And under these rules you elect: |
|---|---|---|
| CSRS | FERS | FERS. |
| CSRS Offset | FERS | |
| Social Security-Only | FERS | No election required. |
| Social Security-Only | CSRS | |
| Social Security-Only | CSRS Offset |