How to use the illinois paycheck calculator
- Enter your gross pay for one pay period and choose how often you are paid.
- Choose your filing status as it appears on your W-4 (Step 1c).
- Enter your IL-W-4 allowances from Line 1 and Line 2 if you filed the form; leave 0 otherwise.
- Add pre-tax items: 401(k) deferrals and health premiums per period.
- Use your W-4 steps (two jobs box, credits, other income, deductions, extra withholding) if you filled them in.
- Read the net pay and the line-by-line deductions for this check.
Illinois: a flat 4.95%
Illinois taxes wages at a flat 4.95%, with no state brackets. Unlike the federal system, there is no standard deduction on the Illinois withholding formula; the reduction comes from the allowances on the employee's IL-W-4. Enter the allowances from your IL-W-4 in the two allowance fields: each Line 1 allowance lowers annual Illinois wages by $2,925 for 2026 and each Line 2 allowance by $1,000. Leave both at 0 if you have not claimed any. This illinois paycheck calculator applies the rules for 2026.
Pre-tax items in Illinois
Illinois starts from federal adjusted gross income, so a traditional 401(k) deferral and section 125 premiums reduce Illinois wages as well as federal ones. The example below defers $140 of a $2,800 check, so Illinois taxes $2,660: $131.67.
Section 125 health premiums come out the same way. A $100 premium and a $140 deferral on one check would remove $240 from both the federal and the Illinois taxable figures, though only the premium also lowers Social Security and Medicare.
How the federal part is worked out
The federal line follows IRS Publication 15-T for 2026. For this example, federal wages are $2,660.00 a period, which annualises to $69,160.00 over 26 pay periods. Step 1(g) takes off $8,600.00 for single filers, leaving $60,560.00. That amount is looked up in the single schedule of annual percentage method tables, the resulting annual tentative tax is divided by 26, and W-4 credits and extra withholding are applied. The result is $245.58 for the period.
Social Security is 6.2% of wages up to $184,500 for the year and Medicare is 1.45% with no cap, plus 0.9% on wages over $200,000. Only section 125 premiums reduce those wages.
Worked example
$2,800 biweekly is $72,800 a year. Federal withholding is $245.58, Social Security $173.60, Medicare $40.60, Illinois $131.67. Net pay is $2,068.55, or $53,782.30 a year. Total withheld is 21.12% of gross.
Compare with a no-tax state
The same check in Texas would net $131.67 more per pay period because Illinois's 4.95% is the only difference.
Checking the result against your pay stub
The Illinois line on your stub should be 4.95% of annualised wages less any allowance amounts, divided by the number of pay periods. If your stub shows less than this page, check that the allowance fields match your IL-W-4. If it shows more, check whether a pre-tax deduction is being treated as taxable. Anything else is a benefit or garnishment, since Illinois has no payroll disability tax for employees and no wage tax in its cities.
Method and sources
Federal withholding follows IRS Publication 15-T (2026), Worksheet 1A, and IRS Publication 15 (2026) for the $184,500 Social Security wage base. Illinois: the 4.95% flat rate is set by the Illinois Income Tax Act (35 ILCS 5/201) and used in Illinois Department of Revenue Form IL-700-T and Form IL-W-4. The 2026 allowance values, $2,925 for each Line 1 allowance and $1,000 for each Line 2 allowance, are from the USDA National Finance Center payroll bulletin on Illinois state income tax withholding for 2026. Illinois cities do not levy a wage tax, but Chicago has other taxes that are not shown. The shared engine is covered by hand-worked Publication 15-T cases in the test suite. Estimate only, not tax advice.
Worked examples
| Example | Input | Result |
|---|---|---|
| Illinois example | Gross pay this period ($): 2800; Pay frequency: biweekly; Federal filing status (W-4 Step 1c): single; IL-W-4 Line 1 allowances: 0; IL-W-4 Line 2 allowances: 0; Pre-tax 401(k) per pay period ($): 140; Health and other section 125 premiums per period ($): 0; W-4 Step 2 box checked (two jobs)?: no; W-4 Step 3 credits, per year ($): 0; W-4 Step 4(a) other income, per year ($): 0; W-4 Step 4(b) deductions, per year ($): 0; W-4 Step 4(c) extra withholding per period ($): 0; Wages already paid this year ($): 0 | Gross pay this period: $2,800.00; Pre-tax deductions: $140.00; Federal income tax withholding: $245.58; Social Security (6.2%): $173.60; Medicare (1.45%): $40.60; Illinois income tax: $131.67; Net pay this period: $2,068.55; Net pay per year: $53,782.30; Total withheld as % of gross: 21.12% |
| Monthly salary, head of household | Gross pay this period ($): 6000; Pay frequency: monthly; Federal filing status (W-4 Step 1c): hoh; IL-W-4 Line 1 allowances: 0; IL-W-4 Line 2 allowances: 0; Pre-tax 401(k) per pay period ($): 300; Health and other section 125 premiums per period ($): 0; W-4 Step 2 box checked (two jobs)?: no; W-4 Step 3 credits, per year ($): 0; W-4 Step 4(a) other income, per year ($): 0; W-4 Step 4(b) deductions, per year ($): 0; W-4 Step 4(c) extra withholding per period ($): 0; Wages already paid this year ($): 0 | Gross pay this period: $6,000.00; Pre-tax deductions: $300.00; Federal income tax withholding: $413.00; Social Security (6.2%): $372.00; Medicare (1.45%): $87.00; Illinois income tax: $282.15; Net pay this period: $4,545.85; Net pay per year: $54,550.20; Total withheld as % of gross: 19.24% |
| Weekly pay with a 401(k) | Gross pay this period ($): 1200; Pay frequency: weekly; Federal filing status (W-4 Step 1c): single; IL-W-4 Line 1 allowances: 0; IL-W-4 Line 2 allowances: 0; Pre-tax 401(k) per pay period ($): 60; Health and other section 125 premiums per period ($): 40; W-4 Step 2 box checked (two jobs)?: no; W-4 Step 3 credits, per year ($): 0; W-4 Step 4(a) other income, per year ($): 0; W-4 Step 4(b) deductions, per year ($): 0; W-4 Step 4(c) extra withholding per period ($): 0; Wages already paid this year ($): 0 | Gross pay this period: $1,200.00; Pre-tax deductions: $100.00; Federal income tax withholding: $90.08; Social Security (6.2%): $71.92; Medicare (1.45%): $16.82; Illinois income tax: $54.45; Net pay this period: $866.73; Net pay per year: $45,069.96; Total withheld as % of gross: 19.44% |
FAQ
What is the Illinois income tax rate?
A flat 4.95% of taxable income.
Does Illinois have a standard deduction on paychecks?
No. Illinois withholding reduces annual wages by $2,925 for each Line 1 allowance and $1,000 for each Line 2 allowance on the IL-W-4, not by a standard deduction.
Are 401(k) contributions taxed in Illinois?
Traditional 401(k) deferrals are excluded from Illinois wages, the same as federal.
Is there a local income tax in Chicago?
No tax on wages is withheld by the city of Chicago.
How do allowances change the result?
Each Line 1 allowance lowers annual Illinois taxable wages by $2,925 and each Line 2 allowance by $1,000, so claiming them raises take-home pay slightly. Enter your counts in the allowance fields.
Does Illinois have a state disability program?
Employees do not have an SDI deduction in Illinois.