Illinois tax notes
- Flat 4.95% state income tax. Property tax averages 2.27% (2nd highest nationally) — the cap-buster for many IL homeowners. PTET available.
Sample tax numbers for Illinois
Quick orientation — use the full calculator for your actual situation.
Tax moves that matter most for Illinois
If you have any pass-through business income (S-Corp, partnership, multi-member LLC), Illinois allows the PTET election that effectively bypasses the federal $10,000 SALT cap on the state income tax portion. Typical savings for high earners: $2k-$15k/year.
At nearly twice the national average, property tax dominates the SALT cap calculation in Illinois. Bunching property tax payments (paying 18 months in one calendar year) can sometimes push you above the standard deduction in alternating years.
At net SE income above ~$80k-$100k, electing S-Corp typically saves $5k-$15k/yr in self-employment tax — the math is largely federal but affects Illinois state tax via PTET (if applicable).
If you have 1099 income, Solo 401(k) lets you contribute up to $70,000/yr (2025) — far more than SEP-IRA in most cases. Reduces both federal and Illinois state income tax.
Run your Illinois numbers
Open the full optimizer with Illinois pre-selected to see your specific tax picture.
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