Why does my bonus get taxed at a flat rate instead of my normal rate?

The IRS classifies bonuses as "supplemental wages." Per IRS Topic 421, employers may withhold at a flat percentage rate on supplemental wages up to $1 million in a year, rather than running it through your normal payroll withholding tables — it's an administrative shortcut for the employer, not your final tax bill.

Is the flat withholding rate my actual tax rate on the bonus?

No. It's just what gets withheld now. Your bonus is taxed at your normal marginal rate(s) once it's combined with the rest of your annual income on your tax return — the flat withholding is reconciled against that real liability when you file.

Could I get money back on a bonus at tax time?

Yes, commonly. If your marginal tax rate is below the flat withholding rate, more was withheld from the bonus than you actually owed on it, and the difference comes back as part of your refund (or reduces what you owe).

Could I owe more instead?

Yes — if your marginal rate is above the flat withholding rate (common for higher earners), not enough was withheld on the bonus, and you'll owe the difference when you file.

Guide

Bonus Tax Withholding vs. Your Actual Tax Rate, Explained

Your employer withholds a flat rate on a bonus; your actual tax on it is determined by your total income at filing time, and the two are rarely the same number.

By Buğra SözeriPublished September 25, 2026

A bonus check that looks smaller than expected usually isn’t a mistake — it’s a flat withholding rate, not your real tax bracket, doing the work. Understanding the difference between what gets held back today and what you actually owe once the bonus is folded into your full-year income avoids both nasty surprises and missed refunds.

Why bonuses are withheld differently from regular pay

Per IRS Topic 421, bonuses fall under “supplemental wages.” Employers have the option to withhold federal tax on supplemental wages at a flat 22% rate for amounts up to $1 million in a calendar year (37% on any portion above $1 million), instead of running the bonus through the same progressive withholding tables used for regular salary. This flat-rate approach is simpler for payroll systems to administer — it is not a statement about how much tax the bonus actually owes.

Withholding now vs. tax owed at filing

The withholding on your bonus check is a prepayment estimate, not the final calculation. Your actual tax liability on that income is determined when your full-year income — salary plus bonus plus anything else — is run through the progressive federal bracket schedule on your tax return. Because a bonus is added on top of your existing income, it’s taxed at your marginal rate — the rate that applies to your last dollar of income — not an average rate across your whole salary.

Worked example

A single filer with a $70,000 base salary and a $10,000 bonus:

	Withholding on the bonus	Actual marginal rate on that income
Bonus withheld at flat supplemental rate	22% federal, per IRS supplemental-wage rules	Determined by where $70k–$80k of income lands in the bracket schedule

If the taxpayer’s marginal bracket on that stretch of income is lower than the flat withholding rate, they’ll see some of that extra withholding returned as a refund. If it’s higher — common for people whose total income crosses into a higher bracket because of the bonus — they may owe additional tax at filing.

What this means practically

Don’t treat the amount withheld from a bonus check as the bonus’s true after-tax value — it’s a placeholder. To estimate your actual liability, add the bonus to your annual gross and run the total through a salary calculator that applies the real marginal brackets, rather than the flat supplemental rate. For how the same withholding mechanics interact with pre-tax 401(k) contributions, see our 401(k) take-home pay guide.

Frequently asked questions

Why does my bonus get taxed at a flat rate instead of my normal rate?: The IRS classifies bonuses as "supplemental wages." Per IRS Topic 421, employers may withhold at a flat percentage rate on supplemental wages up to $1 million in a year, rather than running it through your normal payroll withholding tables — it's an administrative shortcut for the employer, not your final tax bill.
Is the flat withholding rate my actual tax rate on the bonus?: No. It's just what gets withheld now. Your bonus is taxed at your normal marginal rate(s) once it's combined with the rest of your annual income on your tax return — the flat withholding is reconciled against that real liability when you file.
Could I get money back on a bonus at tax time?: Yes, commonly. If your marginal tax rate is below the flat withholding rate, more was withheld from the bonus than you actually owed on it, and the difference comes back as part of your refund (or reduces what you owe).
Could I owe more instead?: Yes — if your marginal rate is above the flat withholding rate (common for higher earners), not enough was withheld on the bonus, and you'll owe the difference when you file.

Sources & references

Authoritative references cited by this piece. Verified by Buğra Sözeri on the dates shown and re-checked at every deploy.

IRS — Topic 421: Supplemental Wages, Withholding for Bonuses and Commissions — IRS guidance on the flat supplemental-wage withholding rate applied to bonuses under a certain size(as of 2026-09-25)
IRS — Federal income tax brackets and rates — Marginal bracket schedule that determines your actual tax owed on total annual income, bonus included(as of 2026-09-25)