Short answer
A FERS buyback is a payment for service credit, not just paperwork.
OPM says military service after 1956 generally requires a deposit to count toward FERS annuity title or computation. OPM also says SF 3108 starts a FERS service-credit payment request, and the application process must begin while still an employee.
Start here
What you actually came to find out
Plain answers first. Sources stay below for checking details.
What does it buy?
Potential credit toward FERS eligibility, computation, or both, depending on the service type.
What does it cost?
OPM says FERS civilian deposits are generally 1.3 percent of salary plus interest. Military deposit rules use their own service trail.
Why does timing matter?
OPM says the process must begin while employed, and near-retirement requests may be handled with the retirement application.
What does the map need?
Deposit estimate, years added, high-3 pay, retirement type, pension change, and how long the pension is expected to pay.
Military service
Deposit after 1956
OPM says military service performed on or after January 1, 1957 requires a deposit to credit the service for FERS annuity purposes.
Source trail: OPM
SF 3108
Start while employed
OPM says employees apply with SF 3108 and must begin the process as an employee.
Civilian deposit
1.3% + interest
OPM says certain FERS civilian deposits are generally 1.3 percent of salary plus interest.
Source trail: OPM
Near retirement
Six months
OPM says not to file a deposit application if retirement is within six months, and to submit the request with the retirement application instead.
Source trail: OPM
The buyback math compares deposit cost with the added service credit, pension increase, eligibility effect, interest, and timing.
Neutral landscape
The shape of the question
The first source is OPM creditable-service guidance because it separates civilian deposit, redeposit, and military service credit.
Source trail: OPM
The second source is SF 3108 because the form is the service-credit payment application path OPM names.
Source trail: OPM
The third source is OPM computation guidance because added service changes the pension only through the FERS formula.
Source trail: OPM
The fourth source is OPM retirement-type guidance because added service can also change eligibility and the supplement path.
Source trail: OPM
Curator core
What the authorities say
These sources are here for the reader who wants to check the work. The plain-English answer stays above them.
Source 01
OPM
Creditable Service
OPM explains FERS civilian service, military service credit, deposits, redeposits, and the SF 3108 service-credit payment process.
Source framing
OPM says military service after 1956 generally needs a deposit to count for FERS annuity title or computation.
Strongest for: official FERS service-credit and deposit rules
Read at OPMSource 02
OPM
SF 3108: Application to Make Service Credit Payment
SF 3108 is the OPM form used to start a FERS service credit payment request.
Source framing
OPM points FERS employees to SF 3108 when applying to make a service-credit payment.
Strongest for: FERS service-credit payment form trail
Read at OPMSource 03
OPM
FERS Information: Computation
OPM explains FERS annuity computation and related retirement benefit mechanics.
Source framing
OPM explains how FERS retirement benefits are calculated from service, age, and salary inputs.
Strongest for: FERS calculation vocabulary
Read at OPMSource 04
OPM
FERS Information: Types of Retirement
OPM explains FERS retirement types, eligibility ages, service rules, and special retirement supplement context.
Source framing
OPM is the official source for FERS retirement eligibility and supplement framing.
Strongest for: FERS retirement eligibility and supplement context
Read at OPMPlain-English forks
The forks people face
Most retirement questions hide a few smaller decisions. These are the practical pieces that change the plan.
What kind of service is being bought back?
Why it matters: Military service, civilian deposit service, and redeposit service are not the same thing.
In real life: This fork decides the rule path.
What to look at: What to look at: OPM creditable-service categories.
Does the time change eligibility?
Why it matters: Extra credit can affect title to retirement, not only the monthly calculation.
In real life: This fork can change the retirement doorway.
What to look at: What to look at: retirement type and service years.
How much does the annuity change?
Why it matters: The added time flows through the high-3 formula.
In real life: This fork turns service credit into annual dollars.
What to look at: What to look at: FERS computation guidance.
When is retirement?
Why it matters: OPM has different handling when retirement is within six months.
In real life: This fork changes the paperwork sequence.
What to look at: What to look at: timing of SF 3108 and retirement application.
Common questions
Quick answers
Short, plain answers for the questions people usually have next. The source trail stays available below.
Can military service count toward FERS?+
OPM says active military service can be creditable if it meets the conditions, and service performed on or after January 1, 1957 generally requires a deposit.
What is SF 3108?+
OPM identifies SF 3108 as the Application to Make Service Credit Payment for FERS.
Can I start the deposit after I leave federal service?+
OPM says the application process must begin as an employee, though payments may continue after separation as long as the separation is not for retirement.
What if retirement is within six months?+
OPM says not to file a deposit application if retirement is within six months and says the request should be submitted with the retirement application.
How does a buyback change the pension?+
Added creditable service can flow through the FERS annuity formula and may also affect retirement eligibility.
Is every buyback worth it?+
The public sources do not answer that alone. The comparison needs deposit cost, interest, added service, high-3 pay, retirement type, and expected pension duration.
How this page is curated
This page uses OPM creditable-service guidance, SF 3108, OPM FERS computation guidance, and OPM retirement-type guidance. It treats the buyback as a pension-input question and avoids deciding whether the payment is worth it for a household.
Read the planner methodologyTrust anchor
Sources used on this page
Every source named above is listed here in one place.
OPM. Creditable Service
https://www.opm.gov/retirement-center/fers-information/creditable-service/OPM. SF 3108: Application to Make Service Credit Payment
https://www.opm.gov/forms/pdf_fill/sf3108.pdfOPM. FERS Information: Computation
https://www.opm.gov/retirement-center/fers-information/computation/OPM. FERS Information: Types of Retirement
https://www.opm.gov/retirement-center/fers-information/types-of-retirement/
Before you act on this
This plan is educational. It is not personalized financial, tax, or insurance advice. Projections illustrate the math, they do not predict the future. Talk to your own licensed financial professional before acting on any of it.