1099 Quarterly Taxes in Illinois (2025-2026)
Illinois has a flat 4.95% personal income tax — one of the simpler state tax setups in the country. For self-employed Illinois freelancers, that means a predictable state tax bill on top of federal + SE tax.
Illinois state income tax (2025)
4.95% flat rate on Illinois taxable income. There are no graduated brackets — your first dollar and your last dollar of income are taxed at the same rate. This is unusual; most states with income tax use progressive brackets.
Illinois personal exemption
Illinois allows a $2,775 personal exemption per filer (2025). This is subtracted from your federal AGI before the 4.95% rate is applied.
Quarterly payment due dates
Illinois follows the federal schedule: April 15, June 16, September 15, 2026, and January 15, 2027. State quarterly is filed via Form IL-1040-ES.
How to pay Illinois estimated taxes
The Illinois Department of Revenue (IDOR) accepts payments via MyTax Illinois at mytax.illinois.gov — free bank transfer. You can also mail Form IL-1040-ES with a check.
Common Illinois freelancer scenarios
An Illinois freelancer making $80,000 net SE income pays approximately:
- Federal income tax: ~$8,500
- Self-employment tax: ~$11,300
- Illinois state tax: ~$3,700 (after personal exemption and ½ SE tax federal AGI adjustment)
- Total: ~$23,500 (29% effective rate)
Chicago and other local taxes
Illinois does not allow cities to levy a personal income tax (unlike NYC). However, certain occupations and businesses in Chicago are subject to specific taxes (transactional taxes, parking, etc.) that don't typically affect freelance income.