FERS Military Service Credit: Buyback Calculator & Decision Guide

If you served in the military before becoming a federal civilian employee, you may be able to credit that time toward your FERS pension — but it requires paying a deposit equal to 3% of what you earned in uniform. For most federal employees, the math strongly favors paying it. The break-even point is typically 3–6 years of retirement income, and then you collect the pension increase for life.

Military Buyback Calculator

What the military buyback is

Federal law allows FERS employees to credit active-duty military service toward their federal pension — adding those years to the FERS service-years multiplier. To unlock that credit, you pay a deposit to OPM equal to 3% of the military basic pay you received during that service period, plus interest if a certain amount of time has passed since you joined federal service.¹

The result is straightforward: if you served 4 years in the military and later retire from a federal job with a $120,000 High-3 average salary, buying back those 4 years adds $4,800/year ($400/month) to your pension for life — at the 1% multiplier. At the 1.1% enhanced rate (for employees retiring at 62 or older with 20+ total years), that grows to $5,280/year.

Who qualifies

Eligibility requires all of the following:¹

• Active-duty military service. Time on active duty with the U.S. Armed Forces (Army, Navy, Air Force, Marine Corps, Coast Guard, Space Force). Inactive reserve time or National Guard duty (not federally activated) generally does not count.
• Honorable or general discharge. Discharges under other-than-honorable conditions are not creditable.
• You are covered by FERS. The deposit must be completed while you are actively employed as a FERS-covered federal civilian.
• You are not receiving military retired pay. If you are already collecting military retirement, you must waive that retirement pay to receive FERS credit for the same period. Exception: certain DoD or other agency civilians may be eligible for a "dual compensation" waiver that allows both under specific circumstances — check with your HR office.²

What happens if you don't pay the deposit

Under FERS, the rule is simple: if you don't pay the deposit, your military service years are not counted toward your FERS pension at all. There is no delayed offset like under CSRS. Your military time just doesn't appear in the pension formula.

This is different from CSRS, where unpaid military service initially counts but then causes a pension reduction when the employee becomes eligible for Social Security at 62. Under FERS, there is no such two-stage mechanism — the time is either credited (deposit paid) or not credited (deposit unpaid), full stop. You still accumulate normal Social Security credits for your military service independently of the FERS deposit decision.³

The 3% deposit formula in detail

The deposit equals 3% of the military basic pay earned during each qualifying period of service, plus interest if applicable.¹ The rate has been 3% under FERS for the full history of the program (unlike under CSRS, where the rate is 7%).

Worked example: A federal employee served 6 years in the Army, earning an average of $38,000/year in basic pay (pay stubs or DFAS earnings records will have the exact figures). Their estimated base deposit:

3% × $38,000 × 6 years = $6,840

If they joined federal service 15 years ago and haven't paid yet, interest has been accruing on that $6,840 — potentially adding $3,000–$5,000 depending on the annual interest rate in each year. Their HR benefits office will compute the exact amount with interest using their actual pay records from DFAS.

Interest: how it accrues

Interest begins accruing on the second anniversary of your entry into FERS-covered employment. If you complete the deposit before the end of the third year (within one year of when interest starts), no interest is charged. After that, interest compounds annually at a rate set each calendar year by the Treasury Secretary, based on the average yield of Treasury securities in the preceding fiscal year.⁴

The practical implication: employees who joined federal service in the 2010s when interest rates were low have accrued modest interest. Employees who joined in the late 1980s or 1990s may have significant interest on a decades-old balance. Either way, your HR benefits office will compute the exact figure — the table above is for illustration.

How the pension increase is calculated

Military service years, once credited via deposit, count exactly the same as civilian federal years in the FERS pension formula:

Annual Pension Increase = Multiplier × High-3 Average Salary × Military Years Credited

The multiplier is 1% unless you retire at age 62 or older with 20 or more total years of creditable service (civilian + military combined), in which case it becomes 1.1%.⁵

Why the 1.1% rate matters more here: If buying back your military time pushes you over the 20-year threshold at 62, you may qualify for the enhanced multiplier on your entire FERS pension — not just the military years. That can be worth far more than the direct pension increase from the buyback alone.

What counts as "active duty" — the reserve time trap

Only periods of active-duty military service count for FERS credit. Inactive National Guard and Reserve time — weekend drills, annual training — does not count. However, periods when you were called to active duty (Title 10 activation, federal emergency orders) generally do qualify. Your Leave and Earnings Statements (LES) from that period and your DD-214 will specify the type of duty.

Some federal employees confuse this with the separate rules for leave without pay (LWOP) during military deployment — that's a different calculation covering active civilian-federal employees who take leave for Guard/Reserve duty. The buyback only applies to military service that predated (or ran parallel to) your federal civilian career under active-duty orders.

The process: how to make the deposit

1. Gather your military earnings records. You'll need your military Leave and Earnings Statements (LES) or a certified earnings statement from the Defense Finance and Accounting Service (DFAS). These show exactly what military basic pay you received in each year.
2. Contact your agency HR Benefits office. Request a military service deposit computation. HR will calculate the exact deposit (3% of each year's basic pay) plus accrued interest based on when you joined FERS-covered employment.
3. Choose a payment method. You can pay via payroll deduction (installments from your paycheck), a lump-sum personal check, or a direct rollover from a tax-advantaged account if certain conditions are met. Payroll deduction is most common — no interest accrues on the remaining balance once you're on a payment plan.
4. Get confirmation from OPM. Once fully paid, your agency updates your Official Personnel File and OPM records the credited service. Request written confirmation before retiring.

TSP coordination: the Rule of 55 angle

If buying back your military service years allows you to reach the minimum retirement age (MRA) with 30 years of creditable service sooner than you otherwise would, it can also move up the date you qualify for penalty-free TSP withdrawals under the Rule of 55. The Rule of 55 applies when you separate from federal service in the calendar year you turn 55 or later (age 50 for LEO/FF/ATC). If you reach MRA+30 earlier by adding military years, you retire sooner, and the Rule of 55 starts sooner too — potentially giving you penalty-free TSP access years earlier than if you had continued as a pure civilian employee.⁶

Military years also count toward FEHB retirement continuation (5-year eligibility test), the FERS supplement calculation (with some nuances), and the 20-year threshold that triggers the 1.1% multiplier — so the downstream effects can significantly exceed the direct pension increase.

When the buyback doesn't make sense

The buyback nearly always pencils out purely on a financial basis — the break-even is usually under 5 years, and most federal retirees collect the pension for 20–30 years. But there are two situations where it may not:

• You're already receiving military retired pay and the waiver math is worse. If you'd have to give up a large military retirement benefit to get a smaller FERS pension increase, the waiver may not be worth it. Model both scenarios before deciding.
• You're very close to retirement and cash-constrained. The deposit (especially with decades of compounded interest) can be a large lump sum. If your TSP and other assets are needed for retirement income and the buyback would deplete them, the liquidity cost may outweigh the pension benefit. This is especially relevant for employees retiring in the next 1–2 years who haven't started installment payments.

Decision framework