Firefighter Overtime Tax: Why Your OT Check Looks Small

On the Job
Written By Adrienne Gaughan
Firefighter Overtime Tax: Why Your OT Check Looks Small

Overtime is not taxed at a higher rate. There's no overtime tax bracket, no OT penalty, no special rate the IRS applies to a strike team check. What you're seeing on a big overtime check is withholding, an estimate that payroll systems deliberately overshoot on large checks, and the difference comes back to you at filing. Here's the mechanism, the proof, and the two things a California firefighter can actually do about it.

This is education, not tax, legal, or investment advice. Tax law changes and your situation is specific. Confirm anything here with a licensed CPA or advisor before acting.

Why the myth survives

Every firehouse has a version of it: "Don't pick up that extra shift, it'll all go to taxes." The myth survives because the evidence looks so convincing. You work a brutal OT pay period, the check arrives, and the take-home percentage is visibly worse than your normal check. Nobody hands you a memo explaining that the extra bite is an estimate, so the natural conclusion is that overtime gets taxed harder.

It doesn't. Two different systems are in play, and confusing them costs firefighters real money in bad decisions: turned-down shifts, panic-driven "tax shelter" purchases, and spending plans built on take-home numbers that were never the real tax.

How your tax is actually calculated

Your actual income tax is computed once a year, on your return, using marginal brackets. All your wages for the year, base and overtime alike, get stacked up, and each layer is taxed at that layer's rate. An overtime dollar is taxed exactly like a base-pay dollar sitting at the same height in the stack. The IRS never knows or cares which dollars were overtime.

It's true that OT can push your top dollars into a higher bracket. But that's only the dollars above the bracket line, at that bracket's rate. Earning more never leaves you with less after tax. The bracket system can't do that.

How withholding works, and why big checks get over-withheld

Withholding is a different machine. Under the aggregate method described in IRS Pub 15 (2026), payroll takes your total pay for the period and annualizes it: it withholds as if you earned that much every period all year. Work a monster OT pay period and the system assumes you're a monster earner all year, so it withholds at the brackets that imaginary annual income would hit.

You aren't that earner. Your real annual income is lower than the annualized fantasy, so those big checks are systematically over-withheld. The system is designed to overshoot rather than undershoot, because the IRS would rather owe you than chase you.

Some employers instead use the flat supplemental rate: 22% federal withholding on supplemental wages (like some OT and specialty pays) up to $1 million cumulative for the year, with a mandatory 37% above that (per Pub 15, 2026). Either way, the number on the check stub is an estimate, not a verdict.

The refund is the proof

Here's the tell. If overtime were truly taxed at a higher rate, the money would be gone. Instead, firefighters with heavy OT years routinely get large refunds. That refund is the over-withholding coming home. You gave the government an interest-free loan all year, and filing is when it gets repaid.

So flip the firehouse math: the question is never "is the shift worth it after the OT tax," because there's no OT tax. The question is what your real marginal rate is on the next dollar, federal plus state, and for almost everyone that still leaves the majority of the shift in your pocket.

What you can actually do

Two levers are legitimate. Neither is exotic.

Tune your W-4, carefully. If you're over-withheld year after year, you can adjust your W-4 so less is taken during the year. Do it with a CPA's guidance, not by guessing at allowances, because high-OT income is lumpy and under-withholding triggers penalties. The goal is a small refund, not a big one and not a bill.

Defer into your 457(b). This is the lever that changes your actual tax, not just the timing. Every dollar deferred into your governmental 457(b) reduces your taxable income now, for both federal and California purposes. The 2026 limit is $24,500, with an $8,000 catch-up at 50+ (per IRS Notice 2025-67). A heavy OT year is precisely the year to raise your deferral percentage, because those dollars would otherwise land in your highest brackets. Full details in the 457(b) for California firefighters.

One thing that won't help your paycheck: the new federal overtime deduction. It's real but narrow, it doesn't change withholding during the year at all, and for most California firefighters the qualified amount is far smaller than the paystub OT line. The full breakdown is in does no tax on overtime apply to firefighters.

The California layer

California adds two pieces to the picture.

A high, wide marginal bracket. A single California firefighter sits in the state's 9.3% marginal bracket from roughly $73,000 of taxable income all the way to roughly $371,000 (2025 figures from third-party transcriptions of the FTB rate schedules; the official 2026 bracket dollars publish in fall 2026). Translation: virtually every OT dollar a mid-career single filer earns pays 9.3% to Sacramento, on top of federal. That's the real cost of the shift, and it's still nowhere near "it all goes to taxes."

SDI, maybe. California's State Disability Insurance is 1.3% in 2026 and uncapped since January 1, 2024 under SB 951 (per the EDD rates page), so where it applies it takes 1.3% of every OT dollar with no ceiling. But many fire agencies aren't in SDI at all: public entity employment is generally excluded unless the employer or unit elected coverage (per EDD DE 231SC). Look at your paystub. If there's no CASDI line, this one isn't part of your math. If there is, it's a real but small piece of why the check looks lighter.

And remember that California conforms to none of the new federal overtime deduction, so the state taxes your OT in full either way.

FAQ

Is firefighter overtime taxed at a higher rate?

No. There's no separate overtime tax rate. Overtime dollars are taxed through the same marginal brackets as every other wage dollar. Big OT checks are over-withheld because payroll annualizes them (per IRS Pub 15 mechanics), and the excess comes back at filing.

Why is so much taken out of my overtime check?

Usually the aggregate method: payroll withholds as if that pay period's total were your pay every period, which pushes withholding into brackets your real annual income never reaches. Some supplemental pay is instead withheld at a flat 22% federal rate (per Pub 15, 2026). Either way it's an estimate, reconciled on your return.

Can working overtime push me into a higher tax bracket and cost me money?

It can push your top dollars into a higher bracket, but only those dollars are taxed at the higher rate. You always keep most of every additional dollar. Earning more can't reduce your after-tax income under the bracket system.

Should I get a big refund every year?

A big refund means you over-withheld and lent the government your money for free. It's not a bonus. If it happens every year, have a CPA help you tune your W-4 so the money shows up in your checks instead.

What actually lowers the tax on my overtime?

Deferring into your 457(b) lowers your taxable income now, federal and state ($24,500 limit for 2026 per IRS Notice 2025-67). The federal overtime deduction can shave a bit for some firefighters at filing, but it's capped, phases out from $150,000 MAGI, and counts far less of your OT than you'd guess.

The real numbers

The overtime tax is a ghost story. The real numbers are a marginal federal rate, 9.3% to California on most OT dollars, maybe 1.3% SDI if your agency's in the system, and an over-withholding estimate that comes back at filing. Once you see the machine, the decision gets simple: take the shift if the job and your body say yes, and make the tax math better with the boring, durable move, the 457(b). For every lever in one place, start with how California firefighters actually reduce their taxes, and join the newsletter for the rest of the money section as it publishes.

Sources

Golden State Firefighter is not affiliated with any government agency, department, or retirement system.

Adrienne Gaughan
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