A Social Security provision primarily of interest to employees and retirees under CSRS is the “government pension offset,” which could affect Social Security benefits they might receive as a spouse or survivor.
The offset will reduce the amount of your Social Security spousal or survivor benefits by two-thirds of the amount of your other annuity. In other words, if you get a monthly CSRS annuity of $3,000, two-thirds of that, or $2,000, must be used to offset your Social Security spousal or survivor benefits. In many cases this severely cuts or even eliminates the Social Security benefit.
However, there are certain exceptions to the offset provision. The key ones still pertinent are:
Anyone whose non-Social Security benefit is not based on his or her own earnings (that is, survivor beneficiaries).
Federal employees, including CSRS-Offset employees, who are mandatorily covered under Social Security.
Federal employees who chose to switch from CSRS to FERS during the open seasons in the 1980s and 1990s when that was allowed.