Do you have prior active duty military service?
If you served in the military and now hold a civilian position, your military time may apply toward your civil service retirement. To buy back your military service, you will have to pay a deposit, in most cases 3% of your base pay earned during your military service if you are FERS, 7% if you are CSRS. If the deposit is paid in full within the first 3 years of being hired as a Federal civilian employee, no interest is owed. If you have been a Federal civilian employee for more than 3 years, you can still pay the deposit, but you will owe interest. The sooner you pay the deposit the less interest you will have to pay, so the sooner you pay the deposit the better.
The Office of Personnel Management (OPM) now requires Military Service Deposits be paid in full before your date of separation or retirement. Since processing time can take up to 6 months, this is not something you can do at the last minute.
Find more information about military buy back, and the steps for paying your military deposit at:
FERS employees: www.abc.army.mil/retirements/FERSPost56.htm.
CSRS employees: www.abc.army.mil/retirements/CSRSPost56.htm.