Illinois Quarterly Tax Calculator 2026
Rates reviewed · Illinois Department of Revenue
Illinois has a flat 4.95% income tax rate — one of the simplest state tax structures. Quarterly payments required if you expect to owe $500 or more.
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Tax Information Notice
This content is for informational and educational purposes only. It does not constitute tax, legal, or financial advice. Tax laws change frequently. Always consult a qualified CPA or Enrolled Agent for your specific situation.
Illinois quarterly tax questions
How much is the quarterly tax for freelancers in Illinois?
Freelancers in Illinois pay federal self-employment tax (15.3% of net self-employment income), federal income tax at their bracket, and Illinois income tax of 4.95% flat. This calculator applies 4.95% as a representative Illinois rate for freelancer-level income; the top marginal rate is 4.95% flat.
When are quarterly estimated taxes due in Illinois for 2026?
Illinois follows the federal estimated tax schedule for 2026 — Q1: April 15, 2026, Q2: June 16, 2026, Q3: September 15, 2026, Q4: January 15, 2027. The Q3 payment is due September 15, 2026.
Do I have to make Illinois estimated tax payments?
Illinois requires estimated payments once you expect to owe $500 or more in state income tax for the year. The state form is Form IL-1040-ES. Payments can be made online through MyTax Illinois. Filing and paying federal estimated tax does not cover the state amount — they are separate payments.
Where do I pay Illinois estimated taxes online?
Illinois accepts online estimated tax payments through MyTax Illinois, run by the Illinois Department of Revenue. Federal payments go through IRS Direct Pay or EFTPS separately.
What happens if I underpay estimated taxes in Illinois?
The IRS charges an underpayment penalty based on the amount underpaid and the number of days late. Paying at least 90% of this year's tax or 100% of last year's (110% if your AGI exceeded $150,000) meets the federal safe harbour. Illinois applies its own interest and penalty on late or short state payments.
State payments are administered by the Illinois Department of Revenue via MyTax Illinois.
Tax Information Notice
This content is for informational and educational purposes only. It does not constitute tax, legal, or financial advice. Tax laws change frequently. Always consult a qualified CPA or Enrolled Agent for your specific situation.