Pre-Retirement
Questions and answers
Except for the last 3 years, the money you erroneously paid into Social Security will remain to your credit in the Social Security fund. The Social Security Administration will include all but those last 3 years in determining your eligibility for, and the amount of, future benefits.
The amount you paid into Social Security for the last 3 years will be transferred to your account in the Civil Service Retirement fund. Your employing agency will pay all additional retirement contributions owed for your CSRS time. It may not go back and bill you for additional retirement deductions when it corrects the error.