The FERS Pension Gap: What Your Pension Actually Covers

Ask a federal employee near retirement how they feel about their pension and you'll often hear some version of: "I'll be fine, I've got the pension." Ask what percentage of their current spending the pension is expected to cover, and the room usually goes quiet.

That quiet is the whole subject of this article. Not because the answer is alarming — for plenty of feds it's genuinely reassuring — but because the number, whatever it turns out to be, is the thing that should decide which of your TSP options deserve your attention. Without it, you're choosing in the dark.

The three pieces

If you're under FERS, your retirement income is built from three parts. It's worth being precise about which ones you actually control.

• Your FERS pension. A defined benefit, paid monthly for life. You don't choose its size; a formula does.
• Social Security. Broadly the same as everyone else's, with some choice about when you claim it.
• Your TSP. The one with real optionality — and the one where the decisions are actually yours.

Notice the asymmetry. Two of the three are largely handed to you. The third is where every meaningful choice lives, which is exactly why it's the one most worth understanding, and — not coincidentally — the one your agency spent the least time on.

What the pension actually is

Conceptually, the FERS pension is a formula. It takes your years of creditable service and your high-3 — the average of your highest three consecutive years of basic pay — and combines them with a multiplier to produce an annual benefit.

We're deliberately not printing multipliers here. Not because they're secret, but because they vary by circumstances — your age at retirement, your years of service, whether you're in a special category like law enforcement or firefighting — and a number pulled from a blog post and applied to the wrong situation is worse than no number at all. OPM publishes the real formulas and the conditions attached to them. Use those.

What's worth internalising is the shape of the thing:

• It rewards longevity of service. More creditable years means a bigger benefit. This is why the difference between leaving at 28 years and 30 years is rarely trivial.
• It's anchored to your high-3, not your final salary. An average of three consecutive years, which is usually your last three but doesn't have to be.
• It's a percentage of that average, not the whole thing. This is the part that surprises people. The pension is designed to replace a portion of your income — a meaningful one, but a portion. It was never built to carry retirement on its own. That's not a defect. FERS was designed as a three-legged structure from the start, and the TSP is one of the legs by design, not by accident.

There are also details that materially change the picture and get skipped constantly: survivor benefit elections reduce the ongoing payment in exchange for continuing it to a spouse; unused sick leave can count toward service; FEHB premiums continue in retirement and come out of somewhere. None of these are exotic. All of them move the number.

The supplement, if you're retiring early

If you retire before you're eligible for Social Security, there's a concept worth knowing: the FERS supplement. Broadly, for those who qualify, it's a payment intended to bridge the stretch between federal retirement and Social Security eligibility, roughly approximating the Social Security portion you've earned through federal service.

Three things about it, in outline:

• Not everyone gets it. Eligibility depends on how and when you retire. Some retirement types qualify; others don't.
• It ends. It's a bridge, not a permanent addition. It stops when you reach the relevant Social Security age, whether or not you claim then.
• It can be reduced if you earn. There's an earnings test. If you're planning a second career, this interacts with it.

The reason it matters for a TSP conversation is that it makes your income lumpy rather than flat. Income that steps down partway through retirement is a different planning problem from income that stays level — and it's a step that people building rough mental models tend to forget entirely. Check OPM for whether it applies to you.

The gap exercise

Here's the exercise. It's arithmetic, it takes an afternoon, and it does more than any sales conversation ever will.

1. Estimate your pension. Use OPM's resources or your agency's retirement counsellor. Get an estimate for your actual planned retirement date, not a rounded guess — and net of the things that reduce it, like a survivor election.
2. Estimate your Social Security, and note when it starts. Your statement gives you figures at different claiming ages. Be honest about which age you'll actually claim at. Mark whether the supplement fills a gap before then, and when it ends.
3. Add them up, as a monthly figure. That's your expected baseline income — the part that arrives whether or not you do anything.
4. Write down what you actually expect to spend. Monthly. Not your current take-home, not a percentage rule of thumb — what you think life costs. Include FEHB, include the mortgage if there is one, include the things that only start once you have time on your hands.
5. Subtract. Baseline income minus expected spending.

Whatever's left is the gap. That's the job your TSP has to do.

Do it twice, incidentally — once for the period before Social Security starts, once for after. The two often look quite different, and it's usually the early years that carry the strain.

Why the gap decides which options matter

Here's why all that arithmetic was worth it. The size of your gap changes which of the five TSP options are even relevant to you.

If your gap is small or negative — your pension and Social Security comfortably cover your spending — your TSP isn't being asked to produce income at all. It's doing some other job: a reserve, a legacy, a fund for the unexpected. Options that convert flexibility into income are answering a question you don't have. The considerations that matter to you are probably about taxes, timing, and what happens to the money after you.

If your gap is large — there's a meaningful monthly shortfall your TSP has to fill — then your TSP genuinely is an income problem, and the questions get sharper. How long does the balance last at that rate of withdrawal? What happens if you live to 95? What happens to your spouse? The options that address duration and predictability become relevant in a way they simply aren't for the first person.

If your gap is somewhere in between — which is most people — it's a matter of proportion, and combinations tend to be where real situations land.

Same five options in all three cases. Completely different conversations. This is why anyone recommending a course of action for "federal employees" as a category, rather than for you, is doing marketing rather than analysis.

Where to go from here

Get your estimates from OPM and the Social Security Administration — the real ones, for your real date. Then read the five options with your gap in mind and notice how differently they read once you have a number attached. The full framework for walking the decision in order is in The TSP Secure Path.

The gap won't tell you what to choose. It will tell you which questions are actually yours — which is a much better place to start than a brochure.