Illinois Paycheck Calculator

Illinois withholds one flat rate on your wages, and that rate does not change with income. The calculator above turns your salary or hourly pay into gross pay for the period, takes out federal tax, Social Security and Medicare, and then applies the Illinois formula using the allowances you enter.

How Illinois paycheck withholding works

The Illinois Department of Revenue publishes the method in booklet IL-700-T, revised December 2025 and effective January 1, 2026. The state tax for a pay period is 4.95% of your wages after subtracting an allowance amount for that period. There are no brackets and no standard deduction, so a $40,000 earner and a $140,000 earner are taxed at the same rate on every dollar above their allowances.

The booklet’s own example is a weekly paycheck of $800 with two Line 1 allowances and two Line 2 allowances. The allowance amount for the week is $150.96, which leaves $649.04 of taxable wages, and 4.95% of that is $32.13.

IL-W-4 allowances on Line 1 and Line 2

Your employer gets the allowance counts from the IL-W-4 you hand in. A Line 1 allowance is worth $2,925 a year and a Line 2 allowance is worth $1,000 a year. The annual total is divided by the number of pay periods to get the amount removed from each check.

Take a worker paid $2,500 every two weeks with one Line 1 allowance and none on Line 2. The allowance amount per paycheck is $112.50, leaving $2,387.50, and Illinois withholds $118.18. With no allowances at all, a $1,000 monthly paycheck loses $49.50, which is just 4.95% of the whole amount.

The IL-W-4 also has a line for extra withholding per pay period. If you owe at filing time or want a bigger refund cushion, that line adds a fixed dollar amount to each check. The three examples below leave allowances at zero so you can see the plain 4.95% effect before you add your own.

Illinois take home pay calculator: what else leaves your check

Social Security takes 6.2% of wages up to $184,500 for 2026, and Medicare takes 1.45% of all wages. Once your wages pass $200,000 in the calendar year, your employer starts withholding an extra 0.9% Medicare tax on the amount above that. Federal income tax follows your W-4, filing status and pay frequency.

Pre-tax deductions such as a traditional 401(k) contribution change the wages used in the formulas. Illinois uses taxable wages after those deductions, and the calculator does the same when you enter them.

Hourly pay and overtime in Illinois

An hourly Illinois worker enters a rate, normal weekly hours and overtime hours. Overtime raises gross pay for that period, and a larger period is treated as a higher annual wage by the federal formula. Illinois, with its flat rate, takes the same 4.95% of every extra dollar. That makes the state line easy to check by hand on an overtime week.

Why an Illinois pay stub can differ by a few cents

The booklet also prints wage-bracket tables. They are built from bracket midpoints, so they land slightly away from the formula. In the booklet’s example of $300 paid weekly with two Line 1 allowances and one Line 2 allowance, the table gives $8.38 and the formula gives $8.33. If your payroll software reads the tables, expect the same few-cent gap.

What the estimate leaves out

We found no Illinois local income tax and no employee-paid state disability or unemployment contribution in the sources we used. The booklet does not say so outright, and we did not check a separate official page, so a line on your stub that is not in this estimate is worth asking your employer about.