Illinois Payroll · Flat 4.95% State Tax · IRS Publication 15-T
Illinois Paycheck Calculator 2025
Estimate your Illinois take-home pay for hourly or salaried work. Illinois withholds a flat 4.95% state income tax after subtracting your IL-W-4 allowances, with no employee unemployment tax and no local wage tax. Uses 2025 IRS Publication 15-T rates.
Pay Details
Check this on Form W-4 if you hold two jobs or your spouse also works. It switches to the higher federal Step 2 withholding schedule.
Pre-Tax Deductions (Optional)
Traditional elective deferral. Lowers federal and Illinois tax.
Cafeteria-plan medical premiums. Lowers federal, Illinois, and FICA wages.
Federal W-4 Adjustments (Optional)
Annual federal dependent credit total (e.g. $2,000 per child under 17)
Federal Step 4c additional withholding per paycheck
Illinois Withholding Allowances (Form IL-W-4)
Basic personal allowances (you, spouse, dependents). Each worth $2,850/yr in 2025.
Additional allowances (age 65+, blindness, estimated deductions). Each worth $1,000/yr.
Optional additional Illinois amount requested on Form IL-W-4.
Illinois income tax is a flat 4.95% applied after subtracting your IL-W-4 allowances. Illinois has no employee-paid unemployment tax and no local wage tax, so those lines never appear.
Enter your pay details and click Calculate to see your take-home pay breakdown.
Want the full Illinois payroll picture, including employer unemployment tax, IL-W-4 mechanics, filing frequencies, and the flat-tax debate? Read the Illinois Payroll Taxes guide.
Illinois Payroll Taxes Guide →Short Answer
This Illinois paycheck calculator estimates net take-home pay after federal income tax withholding, Social Security (6.2%), Medicare (1.45%), and Illinois income tax at a flat 4.95% applied after your Form IL-W-4 allowances. For a single filer earning $65,000 per year paid biweekly claiming one Line 1 allowance, gross pay is $2,500.00 per period and Illinois net take-home is approximately $1,962.97. Illinois has no employee unemployment contribution and no local city wage tax, so the only income taxes on your stub are federal and the flat 4.95% state line.
Key Takeaways
- Illinois income tax is a flat 4.95% on net income. For withholding, the employer applies 4.95% to wages after subtracting your IL-W-4 allowances, so unlike a pure percentage state the allowances do change your paycheck.
- For 2025, each Form IL-W-4 Line 1 allowance is worth $2,850 and each Line 2 allowance is worth $1,000. The employer divides the annual allowance total across your pay periods before applying the 4.95% rate.
- A traditional 401(k) deferral reduces Illinois tax. Because Illinois income tax starts from federal adjusted gross income, a deferral already excluded from federal wages is excluded from Illinois wages too. A $7,800 deferral saves about $386 of Illinois tax. This is the opposite of Pennsylvania.
- Section 125 cafeteria-plan medical premiums reduce federal wages, Illinois wages, and Social Security and Medicare wages.
- Illinois has no employee-paid unemployment tax. Illinois unemployment insurance is funded entirely by employers through the Department of Employment Security.
- Illinois has no local city income tax on wages. There is no Chicago earnings tax and nothing comparable to the Philadelphia Wage Tax or New York City resident tax.
- Bonuses and supplemental wages follow separate federal withholding rules (flat 22% or aggregate method) but the same flat 4.95% Illinois rate. For supplemental pay use the Bonus Tax Calculator and see the Bonus Tax Withholding Guide.
2025 Illinois Paycheck Tax Quick Reference
| Tax | Rate | Wage Base / Threshold | Notes |
|---|---|---|---|
| Federal Income Tax | 10%–37% | No cap | Graduated brackets. Based on W-4 filing status and Publication 15-T percentage method tables. |
| Social Security (OASDI) | 6.2% employee | $176,100 (2025) | Withholding stops at wage base. Employer matches 6.2%. |
| Medicare (HI) | 1.45% employee | No limit | Employer matches 1.45%. |
| Additional Medicare Tax | 0.9% | $200,000 single/HOH; $250,000 MFJ; $125,000 MFS | Employee only. Employer withholds once individual wages exceed $200,000. |
| Illinois Income Tax | 4.95% flat | No cap | Applied after IL-W-4 allowances. No brackets, no standard deduction in withholding math. |
| IL-W-4 Line 1 Allowance | $2,850 each (2025) | Reduces taxable wages | Basic personal allowances: you, spouse, dependents. |
| IL-W-4 Line 2 Allowance | $1,000 each (2025) | Reduces taxable wages | Additional allowances: age 65+, blindness, estimated deductions. |
| Illinois Unemployment (employee) | None | — | Illinois UI is employer-funded only. No employee deduction. |
| Local City Wage Tax | None | — | Illinois prohibits municipal income taxes on wages. |
How This Calculator Works
Hourly Mode: Gross Pay Per Period
Gross pay per period equals the hourly rate multiplied by hours worked per week, then scaled to the pay period. For biweekly pay: hourly rate × hours per week × 2. For weekly: hourly rate × hours per week. For semi-monthly and monthly: hourly rate × hours per week × (52 ÷ periods per year).
Salary Mode: Gross Pay Per Period
Gross pay per period equals annual salary divided by the number of pay periods per year. Weekly: ÷ 52. Biweekly: ÷ 26. Semi-monthly: ÷ 24. Monthly: ÷ 12.
Which Wages Illinois Taxes
Illinois income tax begins with your federal adjusted gross income, so the wages Illinois withholds on are the same wages that are subject to federal income tax withholding. That has a clean, practical result on a paycheck:
- Federal taxable wages = gross − Section 125 medical − 401(k) elective deferral.
- Illinois taxable wages = the same base as federal, gross − Section 125 medical − 401(k) deferral. Both pre-tax items reduce the Illinois base.
- FICA wages (Social Security and Medicare) = gross − Section 125 medical. The 401(k) deferral does not reduce FICA.
This is the opposite of Pennsylvania, where the state taxes 401(k) deferrals on the way in. In Illinois a traditional deferral lowers the state line as well as the federal line, which is why the calculator shows a small Illinois tax saving whenever you enter a 401(k) amount.
Social Security Tax
Social Security is 6.2% of annualized FICA wages up to the $176,100 wage base for 2025. The per-period amount is the annualized Social Security tax divided by pay periods. This calculator does not track year-to-date cumulative wages, so for workers approaching the wage base, actual withholding will stop mid-year once the limit is reached.
Medicare Tax
Standard Medicare is 1.45% on all FICA wages. The calculator adds the 0.9% Additional Medicare Tax on annualized FICA wages above $200,000, matching the employer withholding rule in IRS Topic 560: withholding starts once wages exceed $200,000 in a calendar year regardless of filing status. Final liability on Form 8959 uses filing-status thresholds ($200,000 single/HOH, $250,000 MFJ, $125,000 MFS).
Federal Income Tax Withholding
The calculator follows IRS Publication 15-T Worksheet 1A (Percentage Method for Automated Payroll Systems) for 2025:
- Annualize the per-period gross pay (multiply by pay periods per year).
- Subtract annualized Section 125 medical premiums and 401(k) elective deferrals to get federal taxable wages.
- Add Step 4a other income; subtract Step 4b additional deductions.
- Subtract the line 1g allowance: $12,900 for married filing jointly or $8,600 otherwise. If the W-4 Step 2 box is checked, subtract $0 instead. The result is the Adjusted Annual Wage Amount.
- Apply the Annual Percentage Method table for the W-4 filing status - the STANDARD schedule, or the Step 2 Checkbox schedule when the Step 2 box is checked - then divide the tentative annual withholding by pay periods.
- Subtract Step 3 dependent credits divided by pay periods, then add Step 4c extra withholding.
Illinois Income Tax
Illinois follows the automated payroll method in Booklet IL-700-T. The employer multiplies the number of allowances the employee claimed on Form IL-W-4 Line 1 by $2,850 and the number of allowances on Line 2 by $1,000, adds them together, and divides by the number of pay periods in the year. That per-period allowance is subtracted from Illinois wages, and the remainder is multiplied by 4.95%:
IL tax = 4.95% × ( wages − ((Line 1 × $2,850) + (Line 2 × $1,000)) ÷ pay periods )
Because the rate is flat there are no brackets to walk. The allowances are the only thing that moves the Illinois line for a given wage, and any extra Illinois withholding you requested on IL-W-4 is added on top. The same 4.95% rate applies to bonuses and supplemental wages, which is why an Illinois bonus has a simpler state calculation than a bonus in a graduated state.
No Illinois Employee Unemployment or Local Tax
Unlike Pennsylvania, Illinois collects no employee unemployment contribution; the entire cost of Illinois unemployment insurance falls on employers through the Department of Employment Security. Illinois also prohibits municipal income taxes on wages, so there is no Chicago earnings tax or any city line comparable to the Philadelphia Wage Tax. That leaves an Illinois paycheck with only two income-tax lines, federal and the flat 4.95% state tax, plus FICA.
Real-World Paycheck Scenarios
Scenario 1: Salaried Single Filer in Cook County
Priya earns $65,000 per year at a Chicago marketing firm, paid biweekly, filing single with a standard federal W-4 and claiming one allowance on IL-W-4 Line 1. She has no 401(k) deferral and no cafeteria-plan premiums. Her biweekly gross is $65,000 ÷ 26 = $2,500.00.
Federal withholding detail: Worksheet 1A subtracts the $8,600 line 1g allowance (W-4 Step 2 box not checked) from the $65,000 annualized gross, giving an Adjusted Annual Wage Amount of $56,400. The STANDARD single schedule applies $5,578.50 plus 22% of the amount over $54,875 ($1,525 × 22% = $335.50) = $5,914.00 annual, divided by 26 periods = $227.46. Illinois detail: her one Line 1 allowance is worth $2,850, so Illinois taxable wages are $65,000 − $2,850 = $62,150, times 4.95% = $3,076.42 annual, divided by 26 = $118.32 per period.
Scenario 2: The 401(k) Deferral That Cuts Illinois Tax
Marcus earns $85,000 per year in Springfield, paid biweekly, filing single with one IL-W-4 Line 1 allowance. He defers $300 per period to a traditional 401(k) ($7,800 per year). Because Illinois starts from federal income, the deferral lowers his Illinois line as well as his federal line.
Marcus's federal and Illinois wages are both $77,200 (gross less the $7,800 deferral), while his FICA wages stay at $85,000 because a 401(k) deferral never reduces Social Security and Medicare. If Illinois taxed deferrals the way Pennsylvania does, his Illinois wages would be $85,000 and his state tax would rise by $7,800 × 4.95% = $386.10 per year. In Illinois that money stays in his paycheck now and is taxed later when he draws the retirement income; see the Pension and Annuity Income Tax Guide for how distributions are treated at the back end.
Practitioner Insight
The Illinois question we field most often is some version of "why is my whole paycheck taxed at one rate?" People expect graduated brackets because that is how the federal side works. Illinois is genuinely flat: 4.95% on every dollar of net income, whether you make $40,000 or $400,000. Once a client sees that the only thing moving their state line is the IL-W-4 allowance count, the stub stops looking mysterious. The most common fix is simply confirming the allowance number the employer keyed matches the current IL-W-4 on file.
The second recurring item is workers who moved from Pennsylvania, Indiana, or another neighboring state and carry over the wrong mental model. A client who assumed their 401(k) was fully taxed by the state, as it is in Pennsylvania, is pleasantly surprised in Illinois: the deferral cuts the Illinois line too. The opposite mistake also happens, where someone from a no-income-tax state like Florida or Texas forgets to budget for the 4.95% line entirely and is caught short at filing. We walk new Illinois residents through the state line specifically.
A third one worth flagging: Illinois does not let you claim exempt casually. If income is expected, the flat tax applies, and the personal exemption fully phases out once federal AGI exceeds $250,000 for single filers or $500,000 for joint filers. High earners who kept a large allowance count from an earlier year can end up under-withheld. We check the allowance math against expected income for anyone near those thresholds.
When This Calculator Gives a Less Accurate Estimate
- High earners above the exemption phase-out: The Illinois personal exemption is disallowed once federal AGI exceeds $250,000 (single) or $500,000 (joint). The calculator applies the allowances you enter; at very high incomes the true allowance value may be zero, so remove your allowances to model that case.
- Reciprocal-state commuters: Illinois has reciprocity agreements with Iowa, Kentucky, Michigan, and Wisconsin. If you live in one of those states and work in Illinois, your employer may withhold your home state's tax instead of Illinois 4.95%. This calculator assumes Illinois resident withholding.
- Roth 401(k) contributions: A Roth deferral is a post-tax deduction. It reduces neither federal nor Illinois taxable wages. Do not enter it in the 401(k) field, which models traditional pre-tax deferrals only.
- Non-medical cafeteria benefits: The Section 125 field models qualified medical premiums. Dependent care FSA and other cafeteria elections follow their own federal rules, which then flow through to the Illinois base differently.
- Additional local or transit assessments: Some Illinois payrolls show non-tax items such as union dues or transit benefit deductions. These are not income taxes and are outside this calculator, which models only federal, FICA, and the Illinois 4.95% tax.
- Year-to-date tracking and variable hours: The calculator annualizes a single consistent pay period. Social Security stops mid-year at the wage base, overtime and seasonal hours vary, and bonuses use supplemental federal withholding rules.
Frequently Asked Questions
What is the Illinois state income tax withholding rate?
Illinois levies a flat individual income tax of 4.95% on net income. For payroll withholding, employers apply 4.95% to wages after subtracting the employee's Illinois withholding allowances from Form IL-W-4. Unlike the federal system, Illinois has no tax brackets and no standard deduction in the withholding math, only the flat rate and the allowance subtraction. The same 4.95% applies to regular wages, bonuses, and other compensation.
How much is an Illinois withholding allowance worth in 2025?
For 2025, each basic personal allowance claimed on Form IL-W-4 Line 1 is worth $2,850 per year, and each additional allowance claimed on Line 2 is worth $1,000 per year. The employer multiplies Line 1 allowances by $2,850 and Line 2 allowances by $1,000, divides the total by the number of pay periods in the year, subtracts that from wages for the period, and multiplies the result by 4.95%. The 2025 personal exemption of $2,850 is the standard $2,050 base plus the cost-of-living adjustment. For 2026 the exemption rises to $2,925.
Do 401(k) contributions reduce Illinois state income tax?
Yes. Illinois income tax starts from your federal adjusted gross income, and a traditional 401(k) or 403(b) elective deferral is already excluded from federal taxable wages, so it is excluded from Illinois taxable wages too. A worker deferring $7,800 to a traditional 401(k) reduces Illinois taxable wages by $7,800 and saves about $386 of Illinois tax at the 4.95% rate. This is the opposite of Pennsylvania, where 401(k) deferrals are taxed by the state going in. The deferral still does not reduce Social Security and Medicare wages in either state.
Does Illinois have local city income taxes on wages?
No. Illinois does not allow municipalities to impose a local income tax on wages. Chicago, Springfield, and every other Illinois city collect no local wage or earnings tax, so there is no city line on an Illinois pay stub comparable to the Philadelphia Wage Tax or New York City resident tax. The only income tax withheld from an Illinois paycheck is the federal tax and the flat 4.95% Illinois state tax.
Do Illinois employees pay state unemployment tax?
No. Illinois unemployment insurance is funded entirely by employer contributions to the Illinois Department of Employment Security. Employees pay nothing toward Illinois unemployment, so there is no employee unemployment line on an Illinois paycheck. This differs from Pennsylvania, where employees pay a 0.07% unemployment contribution. Illinois also has no state-run disability insurance or paid-family-leave payroll tax deducted from wages.
How do I fill out Form IL-W-4 allowances?
Form IL-W-4 has two allowance lines. Line 1 is your basic personal allowances: one for yourself, one for your spouse if applicable, and one for each dependent you can claim. Line 2 is additional allowances for you or your spouse being age 65 or older or legally blind, plus any allowances from the estimated-deductions worksheet. Line 1 allowances are each worth $2,850 in 2025 and Line 2 allowances are each worth $1,000. Claiming more allowances lowers the Illinois tax withheld from each paycheck. If you can be claimed as a dependent on someone else's return, you generally claim zero on Line 1.
Does Illinois tax health insurance premiums paid through a cafeteria plan?
No. Employer-sponsored medical premiums paid through an IRC Section 125 cafeteria plan are excluded from federal taxable wages, and because Illinois income tax begins with federal adjusted gross income, they are excluded from Illinois taxable wages as well. Section 125 medical premiums also reduce Social Security and Medicare wages. In Illinois, both a traditional 401(k) deferral and a Section 125 medical premium reduce the state taxable wage base, unlike Pennsylvania where the 401(k) deferral does not.
What is the Social Security wage base for 2025?
The Social Security wage base for 2025 is $176,100. Social Security tax at 6.2% applies to wages up to this amount, and withholding stops once cumulative wages for the year exceed it. Medicare has no wage base limit and continues at 1.45% on all wages. Employers withhold an additional 0.9% Medicare surtax on wages above $200,000 regardless of filing status; final liability thresholds are $250,000 for married filing jointly and $125,000 for married filing separately.
How does an Illinois paycheck compare to other states?
At the same gross salary, an Illinois worker takes home less than a worker in Texas or Florida, which levy no state income tax, because Illinois adds the flat 4.95% state line. Compared with a graduated high-tax state like California or New York, Illinois is simpler and often lighter at higher incomes because the rate never rises with earnings. Illinois is also lighter than Pennsylvania on retirement savers, since Illinois lets a 401(k) deferral cut the state line while Pennsylvania does not. Compare directly with the Texas, Florida, California, New York, and Pennsylvania calculators.
Why does my actual Illinois paycheck differ from this estimate?
This calculator estimates standard federal withholding, FICA, and the flat 4.95% Illinois tax after IL-W-4 allowances. Actual paychecks also reflect post-tax deductions such as Roth 401(k) contributions and garnishments, year-to-date cumulative Social Security tracking, employer-specific payroll adjustments, mid-year W-4 or IL-W-4 changes, and any additional Illinois withholding you requested on IL-W-4. The calculator assumes consistent pay each period and does not track cumulative wages across the year.
What To Do Next
Start by confirming two Illinois-specific numbers before you trust any paycheck estimate. First, pull your most recent pay stub and check whether the state line equals 4.95% of your Illinois wages after your IL-W-4 allowances. If the number is off, the usual cause is an allowance count on file that no longer matches your situation. Second, if you recently moved to Illinois, make sure a current Form IL-W-4 is on file with your employer at all; without one, the employer withholds as if you claimed zero allowances, which over-withholds.
If the allowance count is wrong, the fix is a new Form IL-W-4 submitted to your employer. If you expect federal AGI above $250,000 single or $500,000 joint, remember the Illinois personal exemption phases out entirely at those levels, so a large allowance count can leave you under-withheld.
For the full Illinois employer picture, including the state unemployment wage base and filing frequencies, read the Illinois Payroll Taxes guide. To understand how withholding connects to your year-end liability, see How Payroll Taxes Work and W-4 Withholding Explained. To decode every line on the stub itself, use How to Read a Pay Stub. If you also have self-employment income, the 1099 Tax Calculator estimates the federal side including self-employment tax.
Sources & Editorial Disclosure
- Illinois Department of Revenue, Booklet IL-700-T (2025), Illinois Withholding Tax Tables (flat 4.95% rate; automated payroll method; $2,850 and $1,000 allowance amounts)
- Illinois Department of Revenue, Personal Exemption Allowance ($2,850 for 2025, $2,925 for 2026; $250,000 / $500,000 phase-out)
- Illinois Department of Revenue, How to Figure Illinois Withholding (IL-W-4 required; rate and allowance method)
- Illinois Department of Employment Security, Unemployment Insurance (employer-funded; no employee contribution)
- IRS Publication 15-T (2025), Employer's Tax Guide to Federal Income Tax Withholding
- IRS Topic 751, Social Security and Medicare Withholding Rates
- IRS Topic 560, Additional Medicare Tax
- Social Security Administration, 2025 Wage Base ($176,100)
- Authored by Munib Ur Rehman · Reviewed by Nausheen Shahid, LMN Tax Inc. Not affiliated with the IRS or the State of Illinois. For informational purposes only.