In California, a bonus paid separately from your regular paycheck is typically hit with about 40 percent in combined withholding: 22 percent federal income tax, 10.23 percent state income tax, 6.2 percent Social Security, 1.45 percent Medicare, and 1.3 percent State Disability Insurance. That’s how much is taken out up front. How much your bonus is actually taxed in California depends on your total income for the year, and any gap between the withheld amount and what you truly owe gets settled when you file your return.
What Comes Out of a Bonus Check
The IRS treats bonuses as supplemental wages. When your employer pays a bonus separately from your regular paycheck, federal law lets them apply a flat 22 percent withholding rate to that amount regardless of your usual bracket.1Internal Revenue Service. Publication 15 (2026), (Circular E), Employer’s Tax Guide
California layers its own flat rate on top. The Employment Development Department requires employers to withhold 10.23 percent on bonuses and stock options paid as supplemental wages.2Employment Development Department (EDD). Information Sheet: Personal Income Tax Withholding – Supplemental Wage Payments
Then come the payroll taxes. FICA takes 6.2 percent for Social Security and 1.45 percent for Medicare on the bonus amount.3Internal Revenue Service. Topic No. 751, Social Security and Medicare Withholding Rates California’s State Disability Insurance adds another 1.3 percent for 2026, and since the state eliminated the SDI wage ceiling starting in 2024, every dollar of your bonus is subject to that deduction no matter how much you’ve already earned.4Employment Development Department. Contribution Rates and Benefit Amounts
A $10,000 Bonus, Line by Line
Here’s what withholding looks like for someone earning under $184,500 for the year who receives a $10,000 performance bonus paid on its own check:
- Federal income tax at 22 percent: $2,200
- California income tax at 10.23 percent: $1,023
- Social Security at 6.2 percent: $620
- Medicare at 1.45 percent: $145
- California SDI at 1.3 percent: $130
Total withholding: $4,118. Take-home: $5,882, or about 59 percent of the original bonus.
When the Flat Rates Don’t Apply
The flat 22 percent federal and 10.23 percent state rates only apply when your employer identifies the bonus as a separate payment. If the bonus is combined with a regular paycheck, or the payroll system can’t separate the two, employers use the aggregate method.1Internal Revenue Service. Publication 15 (2026), (Circular E), Employer’s Tax Guide California follows a similar rule: when supplemental wages are paid at the same time as regular wages, the state’s withholding is calculated on the combined total using the standard withholding tables.2Employment Development Department (EDD). Information Sheet: Personal Income Tax Withholding – Supplemental Wage Payments
Under the aggregate method, your employer adds the bonus to your normal pay for that period, then looks up the withholding as if you earned that combined total every pay period. A $5,000 bonus dropped into a $4,000 biweekly paycheck makes the payroll system treat you as though you earn $9,000 every two weeks, or roughly $234,000 a year, which pushes withholding into a higher bracket. The aggregate method often takes out more than you actually owe. It doesn’t change your real tax bill; the excess comes back as a refund when you file.
Higher Earners and the Pieces That Shift
Three thresholds change the math for larger paychecks.
The Social Security portion stops once your total wages for the year reach $184,500 in 2026.5Social Security Administration. 2026 Cost-of-Living Adjustment (COLA) Fact Sheet If your regular salary has already pushed you past that limit before the bonus lands, no additional Social Security tax is withheld from it, and your take-home on a $10,000 bonus improves by $620. Medicare has no wage limit; the 1.45 percent applies to every dollar.
Once your total wages exceed $200,000 in a calendar year, your employer must withhold an Additional Medicare Tax of 0.9 percent on wages above that threshold.3Internal Revenue Service. Topic No. 751, Social Security and Medicare Withholding Rates For married-filing-jointly couples, the actual threshold for owing the tax is $250,000 of combined wages, but employer withholding starts at $200,000 regardless of filing status, and any difference is reconciled on your return.6Social Security Administration. Social Security and Medicare Tax Rates On a $10,000 bonus, that adds $90 to your deductions.
At the very top, if your total supplemental wages from a single employer exceed $1 million in the same calendar year, every dollar above that mark is withheld at 37 percent, matching the top federal rate.1Internal Revenue Service. Publication 15 (2026), (Circular E), Employer’s Tax Guide The first $1 million is still withheld at 22 percent.
Withholding Is Not Your Final Tax Bill
The 22 percent federal and 10.23 percent California rates are prepayments. Your actual tax depends on your total income for the year and which brackets that income falls into.
On the California side, income tax brackets start at 1 percent and climb to 9.3 percent for single filers earning above roughly $72,700, then rise through 10.3, 11.3, and 12.3 percent for higher earners. Income above $1 million is taxed at 13.3 percent, which includes a 1 percent surcharge that funds behavioral health services. If your total income puts you in the 9.3 percent state bracket, the 10.23 percent withholding slightly overpays and the difference comes back at filing. In the 13.3 percent bracket, you may owe more state tax on the bonus.
The same logic runs on the federal side. The 22 percent flat rate matches the federal bracket for single filers earning between roughly $50,400 and $105,700. If your taxable income lands in the 12 percent bracket, the 22 percent withholding overpays and you can expect a refund. If you’re in the 32 or 35 percent bracket, the 22 percent withholding underpays and you may owe when you file.
Which Tax Year Your Bonus Counts For
Bonuses paid at the turn of the year can raise a question about which tax year they belong to. Under federal rules, income is taxed in the year it is made available to you, not necessarily the year you earned it. If your employer credits a bonus to your account in December and you could withdraw it, the bonus counts as income for that year even if you don’t touch it until January.7eCFR. 26 CFR 1.451-2 – Constructive Receipt of Income
If the bonus is subject to restrictions, such as a forfeiture clause requiring you to stay employed through a future date, you generally don’t have to report it until those restrictions lift and the money is actually available.7eCFR. 26 CFR 1.451-2 – Constructive Receipt of Income A December bonus mailed so that you wouldn’t receive the check until January typically counts as January income. The timing affects your bracket for that year, your eligibility for certain credits, and your estimated tax obligations.