Illinois Paycheck Calculator With Bonus: What You Actually Take Home
Use this Illinois paycheck calculator with bonus to see what a bonus really adds to your check. Illinois withholds its flat 4.95% income tax on a bonus, on top of federal withholding and FICA.
Enter your salary and bonus, then switch between a separate bonus check and a bonus added to a regular paycheck to see how each method changes what lands in your account.
Your pay and bonus
Keep the bonus separate from your regular salary.
Bonus take-home pay
22% federal + 4.95% Illinois flat rate.
Withholding is not your final tax. The method your employer uses changes the size of your bonus check, not the tax you owe when you file.
AT A GLANCE
Illinois bonus Example in One Chart
HOW BONUSES ARE WITHHELD
How a Bonus Is Taxed on Your Illinois Paycheck
A bonus is a supplemental wage: ordinary income taxed at your normal rates when you file, but withheld under special rules. On a separate check, the usual Illinois total is about 34.6% of the bonus.
Federal rules let employers withhold a flat 22% on a bonus paid separately from regular wages (37% on supplemental wages above $1 million a year), or add the bonus to a regular paycheck and withhold on the combined amount as if it were paid every period — the aggregate method, which usually holds back more.
Illinois taxes all wages at a single 4.95% rate, and bonuses are wages. There is no separate, higher Illinois supplemental rate: a bonus paid on its own check is withheld at 4.95% of the gross bonus.
When a bonus is added to a regular paycheck, Illinois withholding on the combined check is still 4.95% of the amount above your IL-W-4 allowances. Your allowances were already used up by your salary, so the extra Illinois withholding on the bonus works out to 4.95% under either method. Only the federal side changes between methods.
Illinois exempts traditional 401(k) deferrals from state income tax, so any part of the bonus your plan defers is not withheld at 4.95%. Social Security and Medicare still apply to the deferred amount.
2026 RATES
Illinois Bonus Withholding Rates for 2026
Every line that can come out of a Illinois bonus, with the rate the Illinois paycheck calculator with bonus applies. Rates are for withholding; your final tax is set on your return.
| Withholding line | 2026 rate | Notes |
|---|---|---|
| Federal income tax | 22% flat | 37% above $1 million of supplemental wages |
| Social Security | 6.2% | Stops at the $184,500 wage base |
| Medicare | 1.45% | +0.9% on wages above $200,000 |
| Illinois income tax | 4.95% | 4.95% Illinois flat rate |
| Illinois local income tax | None | No city or county income tax |
WORKED EXAMPLES
Illinois Paycheck Calculator With Bonus: Worked Examples
Bonus take-home pay on a $75,000 salary, single filer, bi-weekly pay, no bonus deferral. The regular bi-weekly paycheck at this salary is about $2,231.72 after tax.
| Bonus | Illinois tax (flat) | Take-home (separate check) | Take-home (aggregate) | Aggregate withholding |
|---|---|---|---|---|
| $1,000 | $50 | $654 | $654 | 34.6% |
| $2,500 | $124 | $1,635 | $1,621 | 35.2% |
| $5,000 | $248 | $3,270 | $3,206 | 35.9% |
| $10,000 | $495 | $6,540 | $5,943 | 40.6% |
| $25,000 | $1,238 | $16,350 | $13,751 | 45.0% |
Reading the table: the aggregate method holds back more up front, not more tax overall. Any excess withholding comes back when you file your federal and Illinois returns.
KEEP MORE
How to Keep More of a Illinois Bonus
In Illinois a traditional 401(k) or 403(b) deferral from a bonus avoids both federal withholding and the 4.95% Illinois tax, and an HSA contribution through a cafeteria plan avoids federal, Illinois, and FICA tax. Every $1,000 deferred from an Illinois bonus keeps about $269.50 of federal and state withholding out of the bonus check (22% + 4.95%).
- Ask HR whether your 401(k) election applies to bonuses, and whether a separate bonus deferral rate is allowed.
- Time HSA or dependent-care FSA contributions so pre-tax room is available in the bonus pay period.
- Check the bonus line on your pay stub: a federal amount well above 22% means the aggregate method was used.
- Do not adjust your W-4 for a one-time bonus; any over-withholding is settled when you file.
USING THE CALCULATOR
How to Use This Illinois Paycheck Calculator With Bonus
- Enter your annual gross salary and the bonus amount you expect.
- Pick your pay frequency — it decides how the aggregate method annualizes the combined check.
- Choose how the bonus is paid: a separate check or added to a regular paycheck.
- Set your federal filing status, your IL-W-4 total, and any 401(k) or pre-tax deductions.
- Compare both methods in the bottom panel to see which one matches your pay stub.
To tell which method your employer used, divide the federal tax withheld on the bonus line of your pay stub by the gross bonus. A result near 22% points to the flat method; a noticeably higher result points to the aggregate method, and the Illinois paycheck calculator with bonus shows both side by side.
RELATED ILLINOIS CALCULATORS
More Illinois Paycheck Calculators
Start from the main Illinois paycheck calculator for regular pay, check a Illinois biweekly paycheck, or use one of the situation calculators below.
COMMON QUESTIONS
Illinois bonus Paycheck Questions
How much is a bonus taxed in Illinois?+
A bonus paid on a separate check is usually withheld at 22% federal, 4.95% Illinois, 6.2% Social Security, and 1.45% Medicare — 34.6% in total. A $5,000 Illinois bonus at those rates leaves about $3,270. Withholding is a prepayment; the final tax is settled on your federal and Illinois returns.
Does Illinois have a supplemental tax rate for bonuses?+
No separate one. Illinois applies its flat 4.95% income tax rate to bonuses, commissions, and other supplemental wages the same way it applies to salary.
Why is the Illinois tax on my bonus the same under both methods?+
Because Illinois has a flat rate. The aggregate method changes federal withholding because federal brackets are graduated, but every additional Illinois dollar is withheld at 4.95% once your IL-W-4 allowances have been applied to your salary.
Is a bonus subject to Chicago city income tax?+
No. Chicago and other Illinois cities do not levy a local income tax on wages, so an Illinois bonus is not reduced by a city income tax.
Do 401(k) deferrals from a bonus avoid Illinois tax?+
Yes. Traditional 401(k) deferrals are excluded from Illinois base income, so they are not withheld at 4.95%. Roth deferrals are taxed. Whether a deferral applies to bonuses at all depends on your plan document.
CALCULATION SOURCES
Sources Behind This Illinois Calculator
This Illinois paycheck calculator with bonus uses the IRS percentage method from Publication 15-T for regular federal withholding, 2026 Social Security and Medicare rates, and the Illinois rules listed below. Each figure on this page is recalculated from those rules rather than copied from another site.
- IRS Publication 15, section 7 (supplemental wages)
- IRS Publication 15-T (percentage method)
- Social Security Administration 2026 wage base
- Illinois Department of Revenue Booklet IL-700-T (2026)
- 35 ILCS 5/201 (4.95% individual rate)
Full assumptions are documented on our methodology page.
Reviewed by: Paycheck Calculator Editorial Team
Last Updated: October 2026
Disclaimer: the Illinois paycheck calculator with bonusproduces estimates for informational purposes only. Your employer's payroll system, W-4 and IL-W-4 entries, local taxes, and year-to-date wages all affect the actual amounts withheld. For advice about your own tax situation, consult a qualified tax professional.