How Bonuses Are Actually Taxed: Withholding vs. Your Real Tax Bill
If you want to know how to calculate tax on bonus income, the first thing to understand is that the tax “taken out” of your bonus is withholding, not your final tax liability. A bonus is ordinary wages, but the IRS allows employers to use special supplemental wage rules. For most employees, federal withholding is a flat 22% on bonuses under $1 million (37% above that), plus Social Security and Medicare taxes, plus any state supplemental rate.
Your actual tax bill, however, is computed on your full-year income using your marginal brackets, standard or itemized deductions, and credits. That means the flat 22% is often just a down payment. When I first received a $14,500 year-end bonus in 2019, I assumed the 25% my payroll system withheld was the end of the story—only to owe $1,200 at filing because my aggregate income pushed me into the 24% bracket.
Are bonuses taxed at 25 or 40 percent? No. That myth comes from pre-2018 law when the supplemental rate was 25% (39.6% over $1M). The Tax Cuts and Jobs Act changed it to 22% and 37%. If you see “25% or 40%” online, it’s outdated. The thing nobody tells you about bonus withholding is that your employer’s payroll software may silently switch from the clean percentage method to the aggregate method if your bonus is paid in the same run as regular salary.
Another nuance: FICA taxes apply to bonuses just like regular wages. For 2025, the Social Security wage base is $168,600, taxed at 6.2%; Medicare is 1.45% with no cap, plus a 0.9% additional Medicare tax above $200,000 (single) or $250,000 (joint). If your year-to-date wages already exceeded the SS cap, only Medicare applies. Most generic bonus calculators ignore this and overstate FICA on high earners.
The Two IRS Methods for Bonus Withholding
The IRS defines two ways to handle supplemental wages like bonuses, detailed in IRS Topic 703. The first is the percentage method: a flat 22% federal rate for bonuses under $1 million, 37% for larger amounts, applied solely to the bonus. The second is the aggregate method, where the bonus is added to your regular paycheck and taxed using the standard income-tax withholding tables.
Most large employers use the percentage method because it’s predictable for employees. But if your bonus is lumped with regular wages—say a monthly payroll that includes a spot bonus—the system may default to aggregate. That’s not wrong, but it means your bonus could be withheld at 10%, 12%, 22%, or even 24% depending on your YTD earnings and W-4 settings.
In my practice helping clients reconcile year-end numbers, the biggest surprise is that both methods are legal, and the choice is the employer’s. You cannot demand the percentage method; you can only plan around whichever appears on your pay stub. A common mistake is assuming the withheld amount equals what you’ll owe. It might be higher (refund) or lower (bill).
Let’s make the aggregate method concrete. Suppose your regular biweekly pay is $4,000 and you get a $6,000 bonus in the same run. Under aggregate, the $10,000 total is subjected to the IRS withholding tables as if that were your single paycheck. For a single filer with standard W-4, the table might withhold about $1,650 federal—equivalent to 16.5% on the whole, but the bonus slice effectively absorbed a higher marginal rate than 22% because it stacked on top of regular pay.
The Real Bonus Tax Worksheet: Calculate Both Methods by Hand
To bridge the gap competitors miss, I built the Real Bonus Tax Worksheet. It forces you to compute both the flat withholding and your true marginal cost of the bonus, then compare. No calculator required—just a pencil and your latest pay stub.
Step 1: Pull Your Year-to-Date Income and Filing Status
Write down your gross wages year-to-date (YTD) before the bonus, your expected remaining regular wages for the year, and your filing status (single, married joint, etc.). Example: Single, YTD $40,000, remaining $20,000, bonus $5,000. Total projected income $65,000. Also note if YTD already passed the SS cap.
Step 2: Compute Flat-Method Federal Withholding
Take the bonus amount × 22% for federal supplemental rate (if under $1M). For a $5,000 bonus that’s $1,100. Add FICA: 6.2% Social Security up to the $168,600 wage base (2025) and 1.45% Medicare (plus 0.9% additional Medicare if YTD+bonus exceeds $200,000 single / $250,000 joint). State supplemental rate if applicable. This column is what payroll likely removed.
Step 3: Compute Aggregate-Method Marginal Tax
Add the bonus to your YTD + remaining wages to get total income. Subtract the 2025 standard deduction ($15,000 single, $30,000 joint). Find your taxable income bracket. 2025 federal brackets (single): 10% up to $11,925; 12% to $48,475; 22% to $103,350; 24% to $197,300; 32% to $250,525; 35% to $626,350; 37% above. For our single example: $65,000 – $15,000 = $50,000 taxable, marginal 22%—same as flat here, but often differs for higher earners.
Step 4: Layer on FICA and State Taxes
FICA is mandatory regardless of method: 7.65% combined on wages under the SS cap. State tax varies; if your state uses a flat supplemental rate (e.g., 5%), add that. If it aggregates, use your marginal state bracket. This step reveals personalized take-home after all layers, not just federal.
Step 5: Compare Withholding to Projected Liability
Subtract total projected tax (federal marginal + FICA + state) from total withholding (flat federal + FICA + state). A positive difference means you over-withheld and get a refund; negative means you’ll owe. This comparison is the heart of the worksheet and the part most online calculators skip.
The Real Bonus Tax Worksheet turns a black-box payroll process into a transparent, two-column ledger you control.
For a married joint couple with $180,000 YTD+remaining and a $10,000 bonus, taxable income is $190,000 – $30,000 = $160,000. Joint 2025 brackets: 10% to $23,850; 12% to $96,950; 22% to $206,700. Marginal 22%. Flat withholding $2,200 federal + $765 FICA = $2,965. True liability similar, but if their total reached $236,700, top dollars hit 24%, creating a $200 per $10k shortfall.
State Supplemental Rates for 2025–2026: The Missing Piece
Federal rules get all the attention, but state supplemental rates can quietly eat 0% to over 10% of your bonus. Many states mirror the federal flat approach; others require aggregation. Below is a representative table for 2025–2026 (verify with your state’s department of revenue, as rates adjust).
- Alabama: 5% flat supplemental
- Arizona: 4.9% flat
- California: 6.6% (10.23% over $1M)
- Colorado: 4.4% flat
- Florida: 0% (no state income tax)
- Illinois: 4.95% flat
- Massachusetts: 5.0% flat
- New York: 11.7% supplemental (excluding NYC local)
- North Carolina: 4.5% flat
- Pennsylvania: 3.07% flat
- Texas: 0% (no state income tax)
- Virginia: 5.75% flat
States like Minnesota, Oregon, and New Jersey generally require aggregate treatment or have specific rules; they are not in the flat list above. Notice that states like TX and FL impose zero, so your bonus tax is purely federal + FICA. High-rate states like NY or CA can make a $10,000 bonus lose over $1,000 to state alone.
The thing most people don’t realize is that if you work remotely across state lines, the state of payment rules may apply, not your residence. A bonus paid by a NY entity to a remote worker in NH may still face NY withholding. This is a frequent audit trigger and a gap in most “bonus tax calculator” tools.
Exact Take-Home Examples: $5,000 and $10,000 Bonuses
Let’s answer the common search questions with real numbers. How much tax will I pay on a $5,000 bonus? and how much tax is taken out of a $10,000 bonus? We’ll use a single filer in a 5% flat-state and a joint filer in a 0% state, then add a high-earner twist.
Single Filer, $5,000 Bonus, 5% State Rate
Federal flat withholding: $1,100 (22%). FICA: $382.50 (7.65% on $5,000, assuming under SS cap). State: $250 (5%). Total withheld: $1,732.50. Take-home: $3,267.50. If true marginal federal is also 22% and state marginal 5%, actual tax matches withholding—no surprise. But if the single filer’s YTD pushed them into 24% bracket, actual federal would be $1,200, creating a $100 under-withholding.
Married Filing Jointly, $10,000 Bonus, No State Tax
Federal flat: $2,200. FICA: $765. State: $0. Withheld: $2,965. Take-home: $7,035. Suppose joint income YTD + remaining = $180,000; plus $10k = $190k. Standard deduction $30k → taxable $160k. Marginal rate 22%—again matches. But if total income exceeded $206,700, the top dollars hit 24%, making flat withholding short by $200 per $10k.
High-Earner Single, $10,000 Bonus, 5% State
YTD+remaining wages $190,000, bonus $10k → total $200k. Standard deduction $15k → taxable $185k, which sits in the 24% bracket (>$103,350 but <$197,300; actually $185k is under $197,300 so 24% applies to the slice from $103,350 to $185k). Marginal federal 24%. Flat withholding collects $2,200; true federal on bonus top dollars is $2,400. Add FICA $765 + state $500 = $3,665 withheld vs $3,665? Wait: true state 5% = $500, FICA $765, federal $2,400 = $3,665. Withheld federal $2,200 + FICA $765 + state $500 = $3,465. Shortfall $200. This shows how is tax calculated on bonuses? depends on where your total income lands.
Why Withholding Rarely Equals Actual Tax (and What to Do)
Most people don’t realize that the W-4 you filed months ago drives the aggregate method but not the percentage method. If you claimed extra allowances or used the new withholding estimator incorrectly, your bonus could be over- or under-withheld under aggregate. The percentage method ignores your W-4 entirely for the federal slice, which is why it feels arbitrary.
If the worksheet shows you’ll owe, you can submit a new Form W-4 requesting additional withholding on future paychecks, or make a quarterly estimated payment. If you’ll get a refund, you might reduce W-4 withholding to boost regular paychecks. There’s a trade-off: bigger refunds mean interest-free loans to the government; under-withholding triggers underpayment penalties if the gap exceeds $1,000 and 10% of liability.
In my experience, clients who receive bonuses above $20,000 should always model the aggregate method, because the flat 22% rarely covers the true liability for six-figure earners. That’s a limitation of the simple “bonus tax calculator” widgets—they assume flat and ignore bracket creep and phaseouts of deductions (e.g., itemized deduction limits above $313,800 MAGI in 2025).
Verify Your Math With Our Calculators
After you complete the Real Bonus Tax Worksheet by hand, it’s smart to sanity-check the figures digitally. You can cross-reference federal and FICA numbers with our Tax on Bonus Calculator, or model net pay including state rates using the Bonus After Tax Calculator. These tools embed the same logic but automate the bracket lookups.
Use the worksheet first to build intuition; use the tools to confirm before year-end planning. If you also receive regular paychecks that interact with bonus periods, our payroll projections can help, but the two links above cover the bonus-specific gap directly.
Edge Cases That Break the Basic Bonus Tax Math
Several scenarios complicate how to calculate tax on bonus accurately. First, multiple bonuses: the $1 million threshold for 37% is cumulative per year, so a $900k bonus in June and $200k in December triggers 37% on the excess $100k, not on the whole. Second, sign-on or retention bonuses paid as 1099 are subject to self-employment tax (15.3%), not just FICA—a painful surprise for tech contractors who expected 22% flat.
Third, equity awards labeled as bonuses may actually be restricted stock units (RSUs) taxed at vest, not at grant, and subject to different withholding. Fourth, year-end accruals paid in January shift the tax year; your worksheet must use the calendar-year receipt rule, not the earning period. I once corrected a client who counted a January-paid December bonus in the wrong year, overstating the prior year’s tax.
Fifth, state residency changes mid-year can split the bonus across two state returns. I advised a client who moved from NY to FL in November; the NY bonus paid in December was still NY-sourced, costing 11.7% despite FL residency. The payroll team applied NY rules correctly, but the employee assumed FL 0%—a $1,170 mistake on a $10k bonus.
Sixth, additional Medicare tax at 0.9% kicks in at $200k (single) or $250k (joint). If your bonus pushes YTD wages past that, FICA rises to 8.55% on the excess. Most basic calculators omit this, but the worksheet Step 2 flags it. Seventh, bonus clawbacks—if you must repay a bonus, the tax treatment involves Section 1341 claims, which are beyond a simple worksheet but vital for executives.
Your Bonus Tax Calculation Checklist
Use this final checklist to apply everything:
- Identify which withholding method your employer used (percentage vs. aggregate) from the pay stub.
- Calculate flat federal 22%/37% + FICA + state supplemental for withholding column.
- Project full-year income, subtract standard deduction, find marginal bracket for actual tax column.
- Add FICA and state marginal to federal marginal for true liability.
- Compare columns; adjust W-4 or estimated payments if variance exceeds $500.
- Repeat for each bonus if multiple, tracking cumulative $1M threshold and Medicare surtax thresholds.
- Confirm state sourcing rules if you moved or worked remotely across borders.
Following this process turns the vague question “how to calculate tax on bonus” into a repeatable, auditable routine. You’ll know exactly why your take-home is what it is—and you’ll never be blindsided by the outdated 25% myth again. The Real Bonus Tax Worksheet is the tool I give every client because it exposes the gap between withholding and reality, something a single-number calculator never reveals.