Explore guides to Illinois tax forms for individuals, businesses, employers, sales and use tax, withholding, and other state tax requirements. Learn what each Illinois tax form is for, who should file it, what information is required, and how to complete and submit your forms correctly.
![Illinois Form IL-1065 — Partnership Replacement Tax Return [thisnextyear]](https://taxformdesk.com/wp-content/uploads/2026/10/out-feat-form-il-1065.jpg)
How to complete Illinois Form IL-1065, the Partnership Replacement Tax Return: the 1.5% replacement tax, the optional 4.95% pass-through entity tax election, due date and six-month extension, Schedule B, estimated payments and where to mail it. Verified against the Illinois Department of Revenue’s 2025 form and instructions.
![Illinois Form IL-1120 — Corporation Income and Replacement Tax Return [thisnextyear]](https://taxformdesk.com/wp-content/uploads/2026/10/out-feat-form-il-1120.jpg)
How to complete Illinois Form IL-1120: who files, the 2.5% replacement tax and 7.0% income tax, due date and 7-month extension, estimated tax, apportionment, line-by-line steps and where to mail it. Verified against the Illinois Department of Revenue’s 2025 form and instructions.
How to fill out Illinois Form RUT-50 for a private party vehicle purchase — Table A and Table B tax amounts, family transfer and gift rates, local tax, and the 30-day deadline.
How to fill out Illinois Form IL-W-4 — the allowance worksheet, claiming exempt status, extra withholding, reciprocal-state rules, and when to give it to your employer.
How to fill out Illinois Schedule ICR — the 5% property tax credit, the 25% K-12 education expense credit capped at $750, the volunteer worker credit, and the caps.
How to fill out Illinois Schedule NR line by line — Column A vs Column B, reciprocal states, sourcing income, prorating the exemption, and the 4.95% tax.
How to fill out Illinois Form IL-1040-X to amend a filed IL-1040 — corrected figures, federal-change rules, required attachments, the 3-year refund limit, and where to mail it.
How to fill out Illinois Form IL-1040 line by line — who must file, the 4.95% flat rate, exemptions, subtractions for retirement income, credits, and the April 15 deadline.