CSRS Offset, explained — the hybrid no one prepares you for

1. The forgotten third system

Ask most feds about retirement systems and you’ll hear about two: the old CSRS and the modern FERS. But there’s a third, sitting quietly between them — CSRS Offset — created to handle a specific group of employees who straddled the 1984 dividing line when Social Security coverage was extended to the federal workforce.

CSRS Offset retirees get a benefit that looks like full CSRS for years, and then changes at 62. Because so little is written for them, many don’t learn how the offset works until they’re staring at a reduced annuity figure and panicking. The reality is far less alarming than the surprise suggests — but only if you understand the mechanics in advance. That’s what this guide is for.

2. Who’s in CSRS Offset

You’re likely CSRS Offset if you have at least five years of civilian CSRS-covered service, you left federal employment, and you were rehired after a break of more than a year that ended after December 31, 1983. At that point, the law required Social Security coverage — but your prior CSRS service meant you weren’t simply moved to FERS. The hybrid was the compromise: keep CSRS, add Social Security, and coordinate the two.

The practical signature of CSRS Offset is that you’re covered by both systems at once. Your retirement eligibility follows ordinary CSRS rules — age 55 with 30 years of service, 60 with 20, or 62 with 5 — and your annuity is computed exactly like any CSRS employee’s. The only thing that makes you different shows up at 62.

3. How you pay for it

Here’s a detail that surprises people: CSRS Offset doesn’t cost you more. You pay the same 7.0% of salary toward retirement that a pure CSRS employee pays — it’s simply divided. About 6.2% goes to Social Security (the standard payroll tax) and the remaining ~0.8% goes to CSRS.

That split is the whole reason the offset exists. You’re funding a Social Security benefit during your offset years and a CSRS annuity, but you’re not paying double. At retirement, the system reconciles the two so you don’t get paid twice for the same service — which is exactly what the age-62 offset does.

4. The annuity and the age-62 offset

At retirement, your annuity is computed under the standard CSRS formula — nothing unusual. If you retire before 62, you receive that full, unreduced CSRS annuity right up until your 62nd birthday. Then the offset begins.

At 62, OPM reduces your CSRS annuity by the Social Security benefit attributable to your offset service. The reduction is the lesser of two formulas, but the one almost always used is simple:

So with a $12,000-a-year Social Security benefit and 20 years of offset service, the offset is $12,000 × 20/40 = $6,000 a year. Your CSRS annuity drops by that $6,000 — and you collect your full $12,000 Social Security benefit separately. The offset never grows beyond your offset years, and once set (assuming you don’t return to offset employment), it doesn’t change.

5. See your offset

Enter your CSRS annuity, your estimated age-62 Social Security benefit, and your years of offset service. The calculator shows your income before 62, your income after the offset begins, and how the total compares — the key reassurance most CSRS Offset retirees need.

6. Why it’s a wash, not a loss

Look closely at the calculator and the point jumps out: your total income at 62 is the same or higher than it was before — it just arrives as two checks instead of one. In the standard example, a $60,000 CSRS annuity becomes $54,000 of CSRS plus $12,000 of Social Security, for $66,000 total. The offset took $6,000 from one pocket and Social Security put $12,000 in the other.

That’s the design intent, written into law: the combination of your reduced CSRS annuity and your Social Security benefit will always be at least what pure CSRS would have paid, and sometimes a bit more. The word “offset” sounds like a penalty, but it’s really a coordination — the government making sure you’re not paid twice for the same years, while guaranteeing you don’t come out behind. Once you see that, the age-62 reduction stops being scary.

7. The delay trap

There is one genuine catch, and it’s about timing. The offset to your CSRS annuity happens at 62 whether or not you actually claim Social Security. The trigger is eligibility, not your application.

So imagine you want to delay Social Security — maybe you’re still working, or you want to grow the benefit by waiting toward 70. Your CSRS annuity is reduced at 62 anyway, but the Social Security check meant to replace that reduction isn’t arriving yet. The result is a real, if temporary, income gap: less CSRS, no Social Security to fill it, until you finally claim. It evens out once you do, but you need to plan cash flow around it.

8. WEP, GPO, and survivors

Two related points round out the picture. First, WEP and GPO — the Windfall Elimination Provision and Government Pension Offset that long haunted federal retirees — were repealed by the Social Security Fairness Act effective in 2025. They no longer reduce benefits for affected retirees or their spouses. And because CSRS Offset service was Social Security–covered to begin with, WEP was already a smaller concern for this group. Just don’t confuse those provisions with the age-62 annuity offset described here — that’s a separate mechanism and it remains fully in effect.

Second, survivors. A CSRS Offset survivor annuity is computed under CSRS rules and can itself be offset when the surviving spouse becomes entitled to Social Security survivor benefits on the same earnings — the same coordination logic, applied to survivors. If you’re electing a survivor benefit, factor this in alongside the broader survivor election decision.

9. Frequently asked questions