Taxes take roughly 20% to 30% out of a typical paycheck in Illinois, and the exact figure depends on your income, filing status, and any pre-tax benefits you use. Three mandatory withholdings account for nearly all of it: FICA payroll taxes for Social Security and Medicare, federal income tax, and Illinois’s flat 4.95% state income tax. Illinois has no local income tax, so those three lines are the whole story on most pay stubs.
FICA Takes a Flat 7.65%
Every W-2 employee pays Federal Insurance Contributions Act taxes, and nothing you put on your W-4 changes the amount. The employee share is 7.65% of gross wages, split between two programs.
Social Security is 6.2% of wages up to an annual cap. For 2026, that cap is $184,500, so earnings above that threshold stop being subject to the 6.2% tax for the rest of the year.1Internal Revenue Service. Topic No. 751, Social Security and Medicare Withholding Rates Medicare is 1.45% of all wages with no cap.2Social Security Administration. Contribution and Benefit Base
High earners also pay an Additional Medicare Tax of 0.9% on wages above $200,000 in a calendar year. It kicks in automatically once your year-to-date pay crosses the threshold, and your employer does not match it.1Internal Revenue Service. Topic No. 751, Social Security and Medicare Withholding Rates Your employer matches the standard 7.65% on its own books, but that match never appears on your paycheck.
Federal Income Tax Is the Biggest Variable
Federal income tax is the largest and most variable deduction on most Illinois paychecks. It uses a progressive bracket system, so higher portions of your income are taxed at higher rates. Your employer estimates your annual tax from your W-4 and withholds a slice of each check to cover it.
Before the brackets are applied, payroll software subtracts the standard deduction from your projected annual wages. For 2026, that deduction is $16,100 for single filers, $32,200 for married filing jointly, and $24,150 for head of household.3Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026 Only income above that amount is taxed.
The 2026 federal brackets for single filers are:3Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026
- 10% on taxable income up to $12,400
- 12% on $12,401 to $50,400
- 22% on $50,401 to $105,700
- 24% on $105,701 to $201,775
- 32% on $201,776 to $256,225
- 35% on $256,226 to $640,600
- 37% on income over $640,600
For married couples filing jointly, each threshold is roughly double the single-filer amount, with 37% starting above $768,700.3Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026
These are marginal rates, which trips people up constantly. A single filer earning $60,000 does not owe 22% on the whole amount. After the $16,100 standard deduction, $43,900 of taxable income gets taxed at 10% on the first $12,400 and 12% on the remaining $31,500. The effective federal rate lands well below 22%.
Illinois Charges a Flat 4.95%
Illinois uses a flat income tax of 4.95% on net income.4Illinois Department of Revenue. Income Tax Rates Whether you earn $40,000 or $400,000, the rate is the same, which makes the state portion easy to estimate.
The 4.95% applies to Illinois net income, which starts with your federal adjusted gross income and is then modified by state-specific additions and subtractions in the Illinois Income Tax Act.5Illinois General Assembly. 35 ILCS 5/203 For most W-2 employees, those modifications are small and federal AGI closely approximates the Illinois base.
Illinois offers no standard deduction. Instead, you get a personal exemption allowance that reduces taxable income before the 4.95% is applied. For 2026, the personal exemption is $2,925 per person, one for you, one for a spouse on a joint return, and one for each dependent.6Illinois Department of Revenue. FY 2026-15 Whats New for Illinois Income Taxes Additional exemptions apply if you are 65 or older or legally blind.
The exemption disappears entirely at higher incomes. If federal AGI exceeds $250,000 for single filers or $500,000 on a joint return, you get no personal exemption at all, with no phase-out in between.7Illinois Department of Revenue. Step 4 – Exemptions
No Local Income Tax on Your Paycheck
Illinois municipalities and counties do not levy local income taxes on wages. Workers in Ohio, Pennsylvania, or New York City can lose an extra 1% to nearly 4% of pay to local income tax. In Illinois, the only income-based taxes hitting your paycheck are FICA, federal, and the 4.95% state tax. Anything else on your pay stub is almost certainly a non-tax item like a garnishment, benefit premium, or union dues.
Pre-Tax Deductions Cut All Three Taxes
Certain deductions come out of gross pay before any tax is calculated, so they shrink the income that FICA, federal income tax, and Illinois income tax are all based on. That is a triple savings, and most Illinois employers offer at least some of these options.
Retirement contributions are the largest lever. If your employer offers a 401(k) or 403(b), you can defer up to $24,500 of 2026 salary before taxes. Workers 50 and older can add $8,000 in catch-up contributions for a total of $32,500, and those ages 60 through 63 get an $11,250 catch-up, for $35,750.8Internal Revenue Service. 401(k) Limit Increases to $24,500 for 2026 Every dollar contributed reduces every tax on the check.
Health insurance premiums paid through your employer typically come out pre-tax under a Section 125 cafeteria plan. So do contributions to a health care flexible spending account, capped at $3,400 for 2026, and to a dependent care FSA. If your pay stub shows a health or dental premium above the tax lines, it is trimming your tax base across the board.
What a Real Paycheck Looks Like
Numbers make this concrete. A single filer earning $60,000 a year with no dependents, no pre-tax deductions, and a standard W-4 would see this on a biweekly paycheck across 26 pay periods:
- Gross pay per period: $2,307.69
- Social Security at 6.2%: −$143.08
- Medicare at 1.45%: −$33.46
- Federal income tax: −$193.08, based on $43,900 taxable income after the $16,100 standard deduction
- Illinois income tax at 4.95%: −$108.66, based on $57,075 after the $2,925 personal exemption
- Total deductions: −$478.28
- Net pay: about $1,829.41
That is roughly 20.7% of gross pay going to taxes. Raise the salary to $100,000 and the effective rate climbs toward 25% as more income falls into the 22% federal bracket. Add a 401(k) contribution and the percentages fall back down. How much taxes take is never a single number. It is a function of income, filing status, and pre-tax elections.
Controlling Withholding on Your W-4
Your employer calculates federal withholding from what you report on IRS Form W-4, and getting the form right is the biggest lever you have over the size of each paycheck. Three inputs matter most.9Internal Revenue Service. Topic No. 753, Form W-4 Employees Withholding Certificate
Filing status sets the brackets and standard deduction your payroll system uses. When both spouses work and select Married Filing Jointly without checking the two-earner box in Step 2(c), each employer assumes the other spouse earns nothing, and the household ends up under-withheld. Dependents lower withholding directly through Step 3, which multiplies qualifying children by the per-child credit. Step 4 offers fine-tuning. Line 4(b) lets you claim expected deductions above the standard deduction, lowering withholding. Line 4(c) lets you request an extra flat dollar amount taken from each check, useful if you have freelance or investment income that is not withheld anywhere else.
Withholding is only an estimate. The actual bill is settled when you file Form 1040. Over-withholding produces a refund, which is your own money coming back without interest. Under-withholding means writing a check, and possibly a penalty.
Penalties for Under-Withholding
If total withholding falls short of what you owe, both the IRS and Illinois can assess penalties. This most often catches dual-income households with uncoordinated W-4s and people with significant non-wage income.
Federally, you avoid the underpayment penalty if you owe less than $1,000 after withholding and refundable credits, or if your withholding covered at least 90% of the current year’s tax or 100% of the prior year’s tax, whichever is smaller.10Internal Revenue Service. Topic No. 306, Penalty for Underpayment of Estimated Tax If your prior-year AGI exceeded $150,000, the prior-year safe harbor rises to 110%.
Illinois runs a parallel system, waiving its late-payment penalty if you paid at least 100% of the prior year’s liability or 90% of the current year’s by the required dates.11Illinois Department of Revenue. Computation of Penalties for Individuals Miss those thresholds and Illinois charges 2% on the underpayment for the first 30 days, rising to 10% after that. Running the IRS Tax Withholding Estimator once a year, and again after any life change, is the simplest way to stay clear of both penalties.