Illinois Quarterly Estimated Tax Payments for Freelancers
Everything self-employed workers in Illinois need to know about estimated quarterly tax payments in 2026.
Illinois Tax at a Glance
Illinois has a flat state income tax rate of 4.95% on all taxable income, regardless of how much you earn. This simplicity makes it easy to estimate your state tax liability. Freelancers pay the same rate whether they earn $30,000 or $300,000. Illinois follows federal estimated tax deadlines. Make your state estimated payments through the Illinois Department of Revenue website (tax.illinois.gov) using Form IL-1040-ES. The flat rate means your state quarterly payment is simply 4.95% of your taxable income divided by four.
Calculating Your Illinois Quarterly Payments
Your total quarterly estimated payment includes federal income tax, self-employment tax (15.3% on 92.35% of net SE income), and Illinois state income tax. Use the TaxCadence calculator with Illinois selected to get your exact quarterly amounts broken down by federal and state.
2026 Due Dates
Estimated tax payments for Illinois follow the federal schedule: Q1 on April 15, Q2 on June 16, Q3 on September 15, and Q4 on January 15 of the following year. Mark these dates to avoid underpayment penalties.
Source: Illinois Dept. of Revenue
Tax rates shown are as of January 2026. Rates and brackets may change due to new legislation. Verify current rates with your state's tax authority. TaxCadence provides estimates for planning purposes only and is not a substitute for professional tax advice.