01
Start with official basic earnings
Use RI 20-97 or an official military-pay estimate. Keep BAH, BAS, bonuses and other allowances outside the deposit base.
Federal retirement deposit case sheet
Military service buyback calculator
Estimate the statutory FERS or CSRS principal, keep interest provenance honest, and see how paid service could change the pension—without inventing a current payoff.
Entries are calculated in this browser. FedUp does not transmit or store your earnings, dates, service history, high-3, payoff or retirement assumptions.
02
Build the statutory principal
Apply the FERS or CSRS percentage to each applicable earnings bucket and preserve the special 1999 and 2000 rates.
03
Separate interest from principal
Classify the grace period and first interest-accrual date, but use an agency payoff once personal interest or payment history matters.
04
Measure pension credit
Compare the annuity with and without paid military service, then show nominal break-even only against the correctly sourced cost.
Principal ledger
Basic earnings first. Interest later.
The ordinary deposit starts with military basic pay for creditable post-1956 service. Separate 1999 and 2000 because Congress temporarily changed the employee percentages. The statutory ordinary principal is rounded using OPM's convention.
| Earnings bucket | FERS | CSRS |
|---|---|---|
| Most post-1956 earnings | 3.00% | 7.00% |
| 1999 military basic earnings | 3.25% | 7.25% |
| 2000 military basic earnings | 3.40% | 7.40% |
Precision boundary
A deadline classifier is not an interest calculator
Every post-1956 period or tour needs its own coverage or qualifying return date and deadline ledger. That period-specific date can identify the two-year grace endpoint, first interest-accrual date and interest-free completion deadline. It cannot reproduce a payoff without historical composite rates, payment receipts, posting history and the agency's exact account record.
01
Period-specific coverage / return date
Start a separate timing ledger for each post-1956 period or tour.
02
Two-year grace endpoint
Interest begins to matter after the grace period.
03
Day before first IAD
Complete payment by the classified deadline to avoid first-IAD interest.
04
Agency payoff
Controls cost once interest or payments enter the record.
One date must not be applied across all tours. OPM's 2026 annual rate is 4.25%, and its composite tables provide date-specific context. Neither number, by itself, authorizes FedUp to reconstruct your accrued interest.
USERRA lane
Use the lesser figure only when the service qualifies
If military duty interrupted creditable civilian employment and reemployment rights were exercised, the deposit can be capped by missed civilian deductions. Enter the official would-have-been and actually-withheld amounts directly; changing contribution categories make a salary-derived shortcut unreliable.
Lane A
Ordinary military principal
Applicable rate × uncovered military basic earnings
Lane B
Missed civilian deductions
Would-have-been deductions − deductions actually withheld
Pension comparison
Recompute the whole formula—not just added years
A purchase can cross a formula threshold. Standard FERS uses 1%, or 1.1% at age 62 or older at separation with at least 20 years. CSRS uses 1.5% for the first five years, 1.75% for the next five, then 2% subject to the ordinary 80% cap. The calculator shows before, after and the threshold change instead of multiplying purchased time in isolation.
This is an unreduced standard-formula comparison.
Treat the age input as age at separation. It does not determine retirement eligibility or retirement path. The calculator excludes the special eligibility, commencement and reduction rules for MRA+10, early and deferred retirement, as well as survivor-annuity reductions. When a reduction applies, it can materially reduce the modeled pension increase and lengthen nominal break-even.
Annual increase
Pension after credit minus pension before credit
Monthly increase
Annual increase divided by 12
Nominal break-even
Selected cost divided by annual increase
Creditability boundaries
Arithmetic can finish while eligibility stays open
These classifications are designed to prompt document review. They do not adjudicate orders, retired-pay exceptions, mixed systems, special categories or survivor cases.
Military retired pay
A waiver is often required, but Chapter 1223 reserve retirement and qualifying combat- or instrumentality-of-war disability exceptions can change the result.
Guard and academy service
Federal activation, state duty, full-time Guard duty, USERRA treatment and academy time do not share one automatic answer. Keep the orders and service evidence for agency review.
Five civilian years
Purchased military time can increase computation service, but it does not replace the minimum civilian-service requirement for a civilian annuity.
Special-category service
Bought military time does not satisfy the covered-service minimum for enhanced LEO, firefighter or similar formulas, and this tool does not apply enhanced rates to it.
FERS supplement
The annuity comparison does not add purchased military service to a FERS annuity-supplement computation.
CSRS Catch-62
For certain pre-October 1982 CSRS cases, unpaid post-1956 service can stop counting at age 62 when Social Security eligibility applies. Agency review controls.
Action file
From records to paid-in-full proof
The calculator is useful only if it advances the actual agency process. Keep each handoff visible.
- 01
Document each service period
Collect DD-214s or equivalent records and separate periods that may need individual creditability or payment review.
- 02
Request certified earnings
Use RI 20-97 and the appropriate military finance center, or begin with the official DFAS military-service-deposit process.
- 03
Submit the civilian deposit application
FERS employees use SF 3108 with its SF 3108A military-deposit supplement. CSRS employees use SF 2803 with its SF 2803A supplement. Submit the system-specific package through the employing agency, and ask the benefits office which package controls a mixed-system case.
- 04
Get the agency payoff
Ask for the amount due, interest-accrual date, payment instructions and payoff-as-of date before relying on break-even math.
- 05
Keep proof of full payment
Retain the paid-in-full confirmation and verify the service appears correctly in the retirement record before separation.
Data strategy
No historical-pay warehouse required
Rules, percentages and source dates are versioned locally. Official earnings and the agency payoff stay user-controlled. Duplicating DFAS rank-by-date history would add maintenance and adjudication risk without making FedUp authoritative, so the shared data platform is not used.
Canonical references
Rules and next steps you can inspect
OPM and federal law control credit and formulas. DFAS supports the earnings process. The employing agency controls the personal payoff.
OPM CSRS/FERS Handbook, Chapter 23Deposit rates, grace period, interest-accrual dates, rounding and agency-payment administration.OPM CSRS/FERS Handbook, Chapter 22Creditable military service, retired-pay, Guard, academy, civilian-minimum and Catch-62 boundaries.OPM BAL 26-101OPM's 2026 COLAs, 4.25% service-credit interest rate, military-deposit percentages and full-payment-before-separation reminder.OPM BAL 26-301The 2026 annual rate, date-specific composite-rate table and agency-receipt deadline used as context, not as a substitute for an agency payoff.OPM BAL 03-105USERRA lesser-of calculation and the official missed-deduction example.5 C.F.R. §§ 842.306–842.307FERS military-service credit and deposit requirements.5 U.S.C. § 8422Statutory FERS deductions and military-service deposit authority.5 C.F.R. Part 831, Subpart UCSRS military-service deposits and interest rules.5 U.S.C. § 8334Statutory CSRS deposit authority and applicable percentages.OPM FERS Annuity ComputationOPM's standard FERS basic-annuity formulas, including the age-62-at-separation and 20-year conditions for the 1.1% factor, plus formulas this tool does not model.5 U.S.C. § 8415Statutory FERS basic-annuity computation, including the standard 1% formula, the 1.1% conditions and separate special computations.5 U.S.C. § 8339Statutory CSRS annuity computation, including the standard tiered formula and other computations and reductions outside this model.DFAS Military Service Deposit EstimatorOfficial starting point for an earnings-based estimate when certified earnings are not yet in hand.DFAS Military Service Deposit ProcessDocuments, earnings requests, agency submission and payment process.OPM Form RI 20-97Request for military earnings information.OPM Forms SF 3108 + SF 3108AThe official FERS service-credit application package and its military-deposit supplement for submission through the employing agency.OPM Forms SF 2803 + SF 2803AThe official CSRS deposit or redeposit application package and its post-1956 military-deposit supplement for submission through the employing agency.
Rules and 2026 rate context verified July 22, 2026. Recheck the annual and composite rate tables by January 15, 2027, and review sooner after a Chapter 22/23, eCFR or statutory change.
Questions
Military service buyback FAQ
Is this an official military buyback calculator?
No. FedUp calculates a planning principal from the official earnings and facts you enter. Your employing agency determines creditability, interest, payment history and the amount currently due. A dated agency payoff controls once supplied.
What pay belongs in a military service deposit?
Use military basic pay for otherwise creditable service. Do not add BAH, BAS, combat pay, flight pay, bonuses or other allowances. Do not include days already covered by civilian retirement deductions.
Can the calculator estimate military buyback interest?
It classifies the grace period, interest start and first interest-accrual date when the entered date supports that classification. It does not manufacture accrued interest from one annual rate because the real payoff depends on personal dates, historical composite rates, payments, receipt timing and agency posting.
What changes for USERRA service?
For qualifying duty that interrupted civilian employment with reemployment rights, the principal can be the lesser of the ordinary military deposit and the civilian deductions that would have been withheld minus deductions actually withheld. Enter those official figures directly.
Does military buyback increase my FERS pension?
Fully paid, creditable military service can add computation service. The result depends on retirement system, high-3, age and total service, including whether FERS crosses the age-62-and-20-year 1.1% threshold. Eligibility and full payment still control.
Can military service replace the five civilian years for FERS?
No. Purchased military service can add retirement computation credit, but it does not replace the civilian-service minimum required for a civilian annuity.
Do I have to waive military retired pay?
Often, but not always. Reserve retirement under Chapter 1223 and certain disability-retirement circumstances can be exceptions. This page flags the issue and leaves adjudication to the agency and OPM.
Does a military buyback affect Social Security?
This tool does not calculate Social Security. A narrow legacy CSRS Catch-62 rule can change credit for unpaid post-1956 military service at age 62 when Social Security eligibility applies; a normal FERS deposit comparison should not be treated as a Social Security estimate.
Should I complete the deposit before leaving federal service?
Payment is normally completed through the employing agency before separation. Survivor and administrative-error situations can be different, but they are exceptions that require agency or OPM review.
Protect the next move
Put the deposit beside the career plan.
Explore private-sector roles matched to federal experience while you decide how service credit fits the transition runway.