2026 Illinois State Income Tax
Effective 2026-04-28
Illinois has a constitutionally-mandated flat income tax (4.95% since 2017) with a per-person personal exemption.
The 2026 Illinois rate
4.95%
Illinois standard deduction (or personal exemption)
The amount Breakeven subtracts from federal AGI before applying the 4.95% rate, by filing status:
| Filing status | Illinois subtraction |
|---|---|
| Single or Married filing separately | $2,850 |
| Married filing jointly | $5,700 |
| Head of household | $2,850 |
Worked examples (Single filer)
| Federal AGI | Illinois taxable | Illinois tax |
|---|---|---|
| $40,000 | $37,150 | $1,838.93 |
| $80,000 | $77,150 | $3,818.93 |
| $150,000 | $147,150 | $7,283.93 |
| $300,000 | $297,150 | $14,708.93 |
The Illinois personal exemption
Instead of a standard deduction, Illinois subtracts a flat personal exemption per person ($2,850 in 2025). The calculator approximates this as a state-level standard deduction by filing status: $2,850 for Single and Head of Household, $5,700 for Married Filing Jointly (single exemption × 2). A household with dependents would have additional $2,850 exemptions per dependent that are not currently factored in, so projected Illinois tax is slightly higher than actual for filers with dependents.
Illinois also phases out the personal exemption at high income: single AGI above $250,000 or MFJ above $500,000 eliminates it. The phaseout is not modeled, so high-income IL filers may see a slightly under-projected state tax.
The flat-rate guarantee
The 4.95% rate is locked into the Illinois state constitution (Article IX, Section 3), which prohibits a graduated income tax. Changing the rate requires legislative action; changing the structure requires a constitutional amendment. The 2020 "Fair Tax" ballot proposal to allow graduated rates was rejected by Illinois voters.
How Illinois stacks with federal tax
Illinois state tax is owed on top of federal income tax. The Breakeven calculator projects both numbers from your year-to-date paychecks once you select Illinois as your state. For the federal side, see the 2026 federal brackets.
Sources
- Illinois Department of Revenue — Income Tax — authoritative source for the rate and Form IL-1040.
- Tax Foundation — State Individual Income Tax Rates — annual cross-reference for state-tax structure and rate stability.
Note on local taxes and SDI. The calculator projects Illinois state income tax only. It does not include municipal or county income tax (where the state allows them) or state payroll surcharges like SDI / paid family leave. If you live or work somewhere with a local income tax, or in a state with an SDI surcharge, your real paycheck withholding will be higher than projected. See the methodology for the full list.
Last cross-checked on 2026-04-28. Verify with the Illinois Department of Revenue if it matters.
Writing about Illinois taxes? Drop this card into your post. Citations welcome.
Canonical reference: https://www.breakeven.tax/brackets/2026/illinois