Q: I retired on an immediate annuity. Can I return to my job and pay back my five months of received annuity and go back into the CSRS retirement system?
A: You could only go back to the position you held if it was open and your former employer wanted to hire you. Because you cannot undo your retirement, if you were hired, it would be as a re-employed annuitant. As such, you would be placed under CSRS, with the option to elect coverage under FERS. In most cases, the salary of your position would be offset by the amount of your annuity.