During years you work under Social Security, your wages are posted to your Social Security record, and you receive Social Security earnings credits based on those wages. These credits are used later to determine your eligibility for Social Security retirement benefits or for disability or survivors benefits if you should become disabled or die.
Earning Social Security credits is a concern not only during current employment but also for prospective future employment after separating from the federal government. CSRS-covered employees especially are interested in this issue because they may wish to work for a certain period in order to earn enough Social Security credits to draw benefits from that system; often they have some credits—through military service, employment before starting a CSRS career or from earnings on the side during it—but not the 40 needed.
That concern is not as significant for employees under CSRS-Offset or FERS because they earn Social Security credits during their government careers. It could be a concern for those who have relatively short working careers, however—for example, those who entered the working world later in life or who had long disruptions of their working careers that could make them fall short of the credits needed.
To gain credits, you must be paying into the Social Security system. It is listed on pay statements as the “Social Security” or “FICA” deduction.