Illinois Tax Calculator
Estimate Illinois state income tax with a flat rate
Note: Illinois generally uses a flat income tax rate. Values and rules can change annually. Educational estimate only.
How to Use This Calculator
Enter taxable income
Use your estimated Illinois taxable income.
Set the flat rate
Use the current IL flat rate or the default illustrative value.
Calculate
See your illustrative state tax estimate.
Formula
Tax = Income × Flat Rate
About Illinois Tax Calculator
This Illinois Tax Calculator provides a simple estimate of state income tax using a flat rate model. Illinois has historically applied a flat income tax rate, meaning your entire taxable income is taxed at the same percentage rather than climbing brackets. While that simplifies the math, individual circumstances—such as deductions, credits, and local taxes—affect your actual liability. This tool is intended for education and rough planning. Always check current Illinois Department of Revenue guidance or consult a professional for precise calculations.
Frequently Asked Questions
Is Illinois a flat tax state?
Yes, Illinois generally uses a flat income tax rate statewide.
Are local income taxes included?
No, this calculator focuses on state income tax only.
Do deductions and credits apply?
They can significantly change your final tax, but are not modeled here.