Facts registry
What is the illinois flat individual income tax rate (TY2025)?
4.95%
The Illinois flat individual income tax rate (TY2025) for TY2025 is 4.95%. Source: Illinois DOR, Income Tax Rates (individual: 4.95% since 2017-07-01). Checked against that source on 2026-08-28.
Where it comes from
- Value
- 4.95%
- Applies to
- TY2025
- Jurisdiction
- US-state
- Last checked
- August 28, 2026
- Registry id
- state.il.flat-income-rate.ty2025
Verified 2026-08-28 against tax.illinois.gov (4.95 percent of net income, effective July 1, 2017). Rate applies to Illinois net income after the per-person exemption ($2,850 in TY2025), which the model does not apply — its input is state taxable income (spec exclusion).
Calculations that use it
When one of these runs, the response returns this constant alongside the result, with its source — so a number in an answer traces back to the notice that set it.
Get it programmatically
The whole registry as JSON — every constant with its value, period, primary source, and check date. No key required.
curl https://worthune.com/api/v1/factsQuestions
Common questions
- What is the illinois flat individual income tax rate (TY2025)?
- The Illinois flat individual income tax rate (TY2025) for TY2025 is 4.95%. Source: Illinois DOR, Income Tax Rates (individual: 4.95% since 2017-07-01). Checked against that source on 2026-08-28.
- Where does this number come from?
- Illinois DOR, Income Tax Rates (individual: 4.95% since 2017-07-01). We record the primary source for every constant our models use, along with the date a person last checked the value against it — in this case 2026-08-28. A figure without a source and a date cannot be told apart from a stale one.
- Which calculations use this figure?
- One Worthune model uses it: state-income-tax. When one of them runs, the response returns this constant alongside the result, with its source, so the number in an answer can be traced back to the notice that set it.
- How do I get this figure programmatically?
- GET https://worthune.com/api/v1/facts returns the whole registry as JSON — every constant with its value, period, primary source, and check date. No key is required.
Related constants
- California 1% bracket top, single (TY2025) — table vintage marker — $11,079
- Massachusetts 4% surtax threshold (TY2025) — $1,083,150
- New Jersey 1.4% bracket top (TY2025) — table vintage marker — $20,000
- New York 4% bracket top, single (TY2025) — table vintage marker — $8,500
- Pennsylvania flat personal income tax rate (TY2025) — 3.07%
- Virginia 2% bracket top (TY2025) — table vintage marker — $3,000
We maintain this registry against its primary sources on a best-efforts basis and version every change publicly. It is reference information, not tax or financial advice — verify against the primary source before relying on a figure. Spotted something wrong or out of date? Tell us at support@worthune.com.