Illinois Property Tax Appeal Guide 2026
To appeal your property taxes in Illinois, you file with your County Board of Review first by the deadline on your assessment notice (shown below). This guide covers how the appeal works, the assessment ratio, what evidence helps, and where to file. General information, not legal advice.
Deadline: Township-specific. County Board of Review windows open on a rolling calendar (Cook County typically begins mid-year and runs through fall); a further appeal to the state PTAB must be filed within 30 days of the Board's written decision.
Missing the deadline permanently waives your appeal for that year. Confirm the exact date on your own assessment notice before acting — it varies by county.
How to appeal your property taxes in Illinois
You file with your County Board of Review first, then the Illinois Property Tax Appeal Board (PTAB). Start by reviewing your assessment notice, gather evidence that your value is too high (recent comparable sales, an appraisal, or condition issues), and submit by the deadline above. Review the official process and forms here: Illinois official filing information.
What is the Illinois assessment ratio?
33⅓% of fair cash value statewide (35 ILCS 200), reached via an annual county equalization multiplier. Cook County is the exception: it classifies property, assessing single-family homes at about 10% of market value and commercial at about 25%.
Illinois property tax at a glance
| Process | appeal |
|---|---|
| Deadline | Township-specific. County Board of Review windows open on a rolling calendar (Cook County typically begins mid-year and runs through fall); a further appeal to the state PTAB must be filed within 30 days of the Board's written decision. |
| You file with | your County Board of Review first, then the Illinois Property Tax Appeal Board (PTAB) |
| Median home value | about $273,000 |
| Median effective tax rate | about 1.95% |
What makes Illinois different
Cook County reassesses each township on a rotating three-year cycle, so increases tend to arrive suddenly. Its classification system — residential assessed far below commercial — concentrates the tax burden on commercial property, and county and press reviews have found lower-value homes over-assessed relative to higher-value ones. Because deadlines are set township-by-township, the single most important step is finding your township's current window.
Outcomes: In Cook County, a majority of self-represented residential appellants received a reduction at the Board of Review in recent reporting (Cook County Board of Review annual report). Results vary by property and year — past outcomes don't predict yours.
Frequently asked questions
When can I appeal my property taxes in Illinois?
Appeal windows are set by township and open on a rolling schedule at your County Board of Review. Check your township's current open and close dates with the Board — in Cook County these are published each year. A further appeal to the state PTAB is due within 30 days of the Board's decision.
What is the Illinois assessment ratio?
Statewide, property is assessed at 33⅓% of fair cash value, adjusted by a county equalization multiplier. Cook County uses a classification system instead — single-family homes are assessed at roughly 10% of market value.
Where do I file an Illinois property tax appeal?
Start at your County Board of Review (Cook County has its own Board). If you disagree with the result, you can appeal to the Illinois Property Tax Appeal Board (PTAB) or file a tax objection in circuit court.
Official sources
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Check your address →This page explains how property-tax appeals work in Illinois in general. This is not legal advice and is not a substitute for a licensed property-tax consultant or attorney. Deadlines and procedures change — confirm the details with your county assessor or tax authority before acting. TrueOwn does not file appeals on your behalf.