Does Going Part-Time Hurt Your Pension?

Going part-time at the end of a federal career is one of the few genuinely attractive options the system offers, and it is usually declined for the wrong reason: the belief that half-time years count as half a year of service and push the retirement date away.

They do not. The rule is misunderstood in both directions at once — part-time service is worth more than people fear in two places, and then something happens at the end that most people have never heard of.

What part-time service does not do

It does not delay your retirement date. Creditable service under 5 U.S.C. § 8411 is calendar time, whatever tour you were on. Five years part-time is five years of service. Eligibility, the five-year vesting test, and the 20-year test for the 1.1% accrual factor all use the unreduced years. The proration is written into the computation section of the statute and nowhere else, which is precisely why it cannot reach your date.

It does not lower your high-3. § 8415(g) says average pay is determined “by using the annual rate of basic pay that would be payable for full-time service in the position”. Your high-3 is computed on the full-time rate of the job you held, not on what you were actually paid. Someone who drops to half time for their last three years has exactly the high-3 they would have had at full time.

What it does instead

The same subsection multiplies the finished annuity by a proration factor: every hour of creditable FERS service you actually worked, over every hour you would have worked had the whole career been full-time.

Note what that is not. It is not the tour you are on now, and it is not the part-time years divided by the whole career. A single part-time stretch dilutes across the entire career rather than reducing the years it covers, which is why the number is usually far gentler than people expect.

A 30-year career, full-time for 25 years and half-time for the last five, on a $98,000 high-3, retiring at 62:

• Proration factor: 91.67%— not 83%, and not anything to do with the five years being “half”.
• Annuity if the career had been full-time throughout: $32,340 a year.
• Annuity as actually worked: $29,645 a year.
• Cost of the arrangement: $2,695 a year, $224.58 a month.

Five years of working half as much cost 8.33% of the pension — and bought five years of half-time salary and five years of half the working week. Whether that is a good trade is a personal question, but it is a much smaller pension question than the folklore suggests.

The timing does not matter

Because the factor is career-wide hours over career-wide hours, it does not care when the part-time years happened. The same five half-time years produce an identical factor of 91.67% and an identical annuity of $29,645 whether they fall at the start of the career or at the end.

That is worth knowing in both directions. Someone who worked part-time while raising children thirty years ago carries exactly the same reduction as someone easing out now — and someone considering easing out is not being penalised for doing it late.

Three things to check before you agree to it

• Your final salary is still your final salary. The high-3 uses the full-time rate, but everything paid as salary — the lump sum for annual leave, your TSP contributions, and the agency match — is based on what you actually earn. The pension is protected; the paycheque is not.
• FEHB coverage continues on a part-time tour, but 5 U.S.C. § 8906 prorates the government contribution for part-time career employees, so the share of the premium you pay rises. Confirm the figure with your agency before agreeing to the tour — it is the one cost of part-time work that is not in the pension arithmetic at all.
• CSRS is a different computation. § 8339(p) credits part-time service performed before 7 April 1986 in full and prorates only what came after, which makes it a two-part calculation rather than a parameter of this one.

Sources

• 5 U.S.C. § 8415(g) — the full-time rate for average pay, and the proration fraction applied to the computed benefit. Text of § 8415
• 5 U.S.C. § 8411 — creditable service, which counts part-time time in full. Text of § 8411
• OPM CSRS/FERS Handbook, Chapter 55 — computation for part-time employees. Chapter 55 (PDF)

Figures computed with lib/fers-part-time.js, which builds the denominator on the 2,087-hour work year of 5 U.S.C. § 5504(b) — the same constant behind the sick leave chart. CSRS part-time service is excluded rather than approximated, for the reason given above.

This guide is informational only. It is not financial, tax, or legal advice, and FedAnnuity is not affiliated with OPM or the U.S. government. Retirement rules turn on the specific facts of a career, and only your agency and OPM can give you a binding figure.

Last reviewed: August 2026 · Against 5 U.S.C. §§ 8415(g) and 8411, and OPM Handbook Chapter 55.