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Service credit deposit

FERS deposit calculator

This FERS deposit calculator estimates what it costs to buy back civilian service: a deposit for time with no retirement deductions, or a redeposit of a refund you took. It applies OPM's base, 1.3 percent of basic pay under FERS or 7 percent under CSRS, or the refund itself, then compounds interest at OPM's rate for each year until the year you plan to pay.

The calculator

What the calculator shows

  • The deposit base, 1.3 percent of basic pay under FERS, 7 percent under CSRS, or the refund for a redeposit.
  • Interest compounded each year at OPM's published rate for that year, with the first and last rates shown.
  • The total due if paid in the year you pick.
  • Any year without a published rate, listed so you can see what the estimate left out.
  • What the payment buys under your system, credit in the annuity or removal of a reduction.
  • The form to file, SF 3108 for FERS or SF 2803 for CSRS.

Your inputs

Prefilled with an example so the result is never empty. Change any number; the result updates as you type.

Educational estimate on the assumptions you entered

$4,290

deposit plus interest if paid in 2026

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Deposit base, 1.3% of basic pay
$780
Interest
$3,510 over 38 years, accrued each December 31 at OPM's rate for that year and compounded (8.375% in 1988 to 4.375% in 2025); none in the year you pay in full
Years with no published rate
None
What it buys
Credit for the service in your annuity computation and eligibility
Form
SF 3108 through your agency HR

Assumptions behind this estimate

  • Interest runs by whole calendar years, posted each December 31 from the midpoint year of the service (or the refund year) through the year before you pay, compounded once a year. OPM prorates the first partial year; the estimate charges it in full, so it runs slightly high.
  • The year you pay carries no interest when the deposit is paid in full by its last business day, and the estimate assumes you do.
  • CSRS deposits for service before October 1, 1982 carry 3 percent interest for the whole period under OPM's rules, and the estimate applies that rule when the midpoint year is 1982 or earlier.
  • CSRS uses 7 percent. Service before 1970 used lower percentages, and law enforcement and firefighter service after 1974 used 7.5 percent.
  • One period at a time. Run the estimate once for each period of service or each refund.
  • Military deposits are not included. They use a different base and interest rule; see the military buyback calculator.
  • Years after 2026 have no published rate yet and are not charged; OPM publishes each new rate in the fall.

Educational estimate on the assumptions you entered, not a projection or a promise and not OPM's official computation. FFEBA is an education organization, not a financial advisor, and does not give personalized financial, tax or legal advice.

Inputs you will enter

  • Retirement systemFERS or CSRS, the system you retire under. It sets the deposit percentage and the rules for what the payment buys.
  • What you are payingDeposit for service with no retirement deductions, such as a temporary appointment, or Redeposit of a refund you took when you left a job.
  • Basic pay earned during that serviceUsed for a deposit. The total basic pay for the nondeduction period, from your SF-50s or agency pay records.
  • Refund amount you receivedUsed for a redeposit. The retirement deductions refunded to you, from the refund notice or OPM's records.
  • Midpoint year of that service, or the refund yearFor a deposit, the calendar year at the midpoint of the nondeduction service, which is where OPM starts the interest clock. For a redeposit, the year the refund was paid.
  • Year you plan to payThe calendar year you expect to pay in full. Interest runs through this year.

How we compute it

The base comes first. A FERS deposit is 1.3 percent of basic pay earned during the nondeduction service, regardless of when it was performed. A CSRS deposit is the deductions that would have been withheld, 7 percent of basic pay for service from January 1970 (OPM CSRS and FERS Handbook, chapter 21, retrieved 2026-10-13). A redeposit is the refund itself.

Interest compounds once a year. OPM starts it at the midpoint of the service period, or on the refund date, posts it each December 31 and charges none for the year in which you pay in full by the last business day. We charge it the same way, for each December 31 from the midpoint year through the year before you pay: 3 percent for years through 1984 and the Treasury variable rate for each year from 1985, the rate OPM applies to civilian service credit accounts (OPM, retrieved 2026-10-13). OPM's own computation starts interest at the midpoint of each period of nondeduction service, or on the refund date for a redeposit, and charges none for a year in which payment in full reaches it by the last business day of that year (OPM CSRS and FERS Handbook, chapter 21, retrieved 2026-10-13). Your bill can land above or below this estimate for those reasons.

What the payment buys depends on your system. Under FERS, nondeduction service before January 1, 1989 is creditable for eligibility and the annuity only with the deposit, and nondeduction service on or after that date generally cannot be bought at all (OPM, retrieved 2026-10-13). Unpaid refunded FERS service still counts toward eligibility but not the annuity. Under CSRS, unpaid nondeduction service before October 1, 1982 still counts, but the annuity is reduced by 10 percent of the deposit due, interest included; unpaid service after September 30, 1982 is left out of the annuity computation. A CSRS refund for service ending before March 1, 1991 leaves the service credited with a permanent actuarial reduction if unpaid; for later refunds, unpaid service is left out of the computation (OPM, retrieved 2026-10-13).

1.3%FERS deposit base, share of basic pay for nondeduction serviceOPM, retrieved 2026-10-13
7%CSRS deposit base for service from January 1970OPM, retrieved 2026-10-13
3%Interest for years 1948 through 1984OPM, retrieved 2026-10-13
4.375%Interest rate for calendar year 2025OPM, retrieved 2026-10-13
4.25%Interest rate for calendar year 2026OPM, retrieved 2026-10-13

A worked example

A FERS employee took an $8,000 refund of retirement deductions in 2024 after leaving a job, came back, and plans to redeposit it in 2026. The base is the refund, $8,000. Interest posted on December 31, 2024 at 3.75 percent brings it to $8,300.00, and interest posted on December 31, 2025 at 4.375 percent brings it to about $8,663.13; nothing is charged for 2026 if it is paid in full that year, so the estimate is $663.13 of interest on these inputs.

If that refund covered 4 years of service and the high-3 is $90,000, restoring those years adds 4 x 1% x $90,000 = $3,600 a year to the basic annuity at the 1 percent rate. The redeposit equals a little under 2 1/2 years of the added annuity. A deposit works the same way from a different base: $40,000 of basic pay in a temporary job whose midpoint fell in 1987 gives a FERS deposit base of $40,000 x 1.3% = $520 before interest, and about $3,118 with 39 years of interest at OPM's published rates if paid in 2026.

What to do with your estimate

Put the years the payment restores into the FERS pension estimator and compare the yearly amount they add with the total due here. For the rules behind each system, read the FERS guide or the CSRS guide. Military time has its own estimate in the military buyback calculator, and every other estimator is on the federal benefits calculators page.

FFEBA is an education organization. If you want someone to look at your own numbers, we can match you with a Federal Retirement Consultant (FRC), a professional trained on federal benefits. The FRC designation is listed with FINRA. The first review is free, nothing is booked until you choose a time, and you are never obligated to work with anyone we introduce. Get matched with an FRC.

Questions about this calculator

How much is a FERS deposit for service with no retirement deductions?

The deposit is 1.3 percent of the basic pay you earned during the nondeduction service, plus interest, whenever the service was performed (OPM CSRS and FERS Handbook, chapter 21, retrieved 2026-10-13). Only nondeduction service before January 1, 1989 can be bought this way, with narrow exceptions such as Peace Corps and VISTA service.

What interest rate does OPM charge on civilian service deposits?

OPM applies the Treasury rate set each calendar year: 4.25 percent for 2026 and 4.375 percent for 2025 (OPM, retrieved 2026-10-13). Years through 1984 carry 3 percent, the variable rate starts January 1, 1985, and interest compounds annually on December 31.

Is there an interest-free period for a civilian deposit?

Not a multi-year one. OPM charges no interest for a year in which payment in full reaches it by the last business day of that year, and no additional interest if a billed balance is paid by December 31 of the year the bill is issued (OPM, retrieved 2026-10-13). Interest otherwise keeps compounding each December 31.

What happens if I do not pay a FERS redeposit?

Refunded FERS service still counts toward your eligibility to retire, but it is left out of the annuity computation, which lowers your annuity and any survivor annuity (OPM, retrieved 2026-10-13). Paying the redeposit puts the service back into the formula.

Is a civilian service deposit worth paying?

It depends on your numbers. Each year of FERS service the deposit restores adds 1 percent of your high-3 to the yearly annuity, or 1.1 percent at 62 with 20 years. The calculator shows the total due; compare it with the yearly amount the service adds in the FERS pension estimator.

Which form do I use to make a deposit or redeposit?

FERS employees use SF 3108 and CSRS employees use SF 2803. If you are within six months of retirement, OPM asks you to send the request with your retirement application (OPM, retrieved 2026-10-13). Military deposits are a separate process.

Reviewed by the FFEBA education team. Last reviewed October 2026.

Sources

  1. U.S. Office of Personnel Management, FERS service credit, retrieved 2026-10-13
  2. U.S. Office of Personnel Management, CSRS service credit, retrieved 2026-10-13
  3. U.S. Office of Personnel Management, CSRS and FERS Handbook, chapter 21 (service credit payments for civilian service), retrieved 2026-10-13
  4. U.S. Office of Personnel Management, Benefits Administration Letter 26-301, Calendar Year 2026 Interest Rate (November 2025), retrieved 2026-10-13
  5. U.S. Office of Personnel Management, Benefits Administration Letter 25-301, Calendar Year 2025 Interest Rate (November 2024), retrieved 2026-10-13
  6. U.S. Office of Personnel Management, FERS creditable service, retrieved 2026-10-13

Every government figure on this page carries its source and retrieval date. Worked examples are educational estimates on the assumptions shown, not a projection of any person's benefit. FFEBA is an education organization, not a financial advisor.

Keep reading

Read the rule behind the math.