You need five years of service to be vested in the retirement system; only after you are vested in the retirement system will you be eligible for an annuity under any circumstances.
That means five years of actual service. Other employment – even active duty service in the armed forces– doesn’t count toward that threshold. Once you meet the five-year requirement, military service can count under certain circumstances if you make a required deposit. So does unused sick leave. But not private sector employment.
If you have at least five years of service but fewer than 10 when you leave government, you can retire at age 62.
If you have at least 10 years, you could retire at your MRA (minimum retirement age, which ranges between 55 and 57 depending on your year of birth—currently 56). However, your annuity would be reduced by 5 percent for every year you were under age 62. You could reduce or eliminate that penalty by postponing the receipt of your annuity to a later date.
If you have at least 20 years, you could retire on a penalty-free annuity at age 60.
If you have at least 30 years, you could retire at your MRA.
If you have at least five years of service but fewer than 20 when you leave government, you can apply for retirement at age 62.
If you have at least 20 years, you could retire at age 62.
If you have at least 30 years, you could retire at age 55.
What happens if you leave government before hitting that five years and you won’t have any title to an annuity?
If you don’t intend to return to government service, you could take a refund of your retirement deductions. However, if you know you’ll be coming back (or are undecided), it makes sense to leave your retirement deductions in the fund.
If you do later come back, you wouldn’t have to redeposit the money, plus accrued interest, to get credit for that time. However, if you don’t come back, you can ask for a refund later, which you’ll get with accrued interest.
ask.FEDweek.com: Calculating a Federal Annuity – FERS and CSRS