What is the property tax appeal deadline in Illinois?

30 days after the publication of the assessment list (varies by county, typically summer). Typical deadline month: August. Always verify the current deadline with your local assessor as dates can change.

What is the success rate for property tax appeals in Illinois?

An estimated 53% of property tax appeals in Illinois result in a reduction. This is based on Lincoln Institute research and state-reported data. Success rates are highest when appeals are supported by recent comparable sales.

2026 data Free guide Illinois

Illinois Property Tax Appeal Guide

Q: How do I appeal my property tax in Illinois?

In Illinois, file your appeal with the County Board of Review. The typical deadline is 30 days after the publication of the assessment list (varies by county, typically summer). The filing fee is $0. Start by contacting your assessor informally, then follow the formal process if unresolved.

How to challenge your property tax assessment in Illinois — deadlines, process, and a savings calculator.

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By Kiznis Studio Editorial · May 2026

August

Typical Deadline

Filing Fee

~53%

Est. Success Rate

County Board of Review

Appeal Body

What This Data Tells Us About Appeals in Illinois

In Illinois, property tax appeals are filed with the County Board of Review. The typical window is 30 days after the publication of the assessment list (varies by county, typically summer), with the deadline most commonly falling in August. Filing fees reported for this state are $0, and Lincoln Institute research plus state-reported data suggest roughly 53% of appeals result in some reduction when supported by comparable sales or documented errors.

Cook County (Chicago) has its own Board of Review with specific deadlines by township. Illinois assesses at 33.33% of fair market value. Appeals are driven by the gap between a parcel's assessed value and its actual market value — the calculator below turns that gap into an annualized dollar figure at your effective tax rate. The strongest evidence is three to five arms-length comparable sales from the past six to twelve months, plus documentation of any factual errors in the assessor's record (square footage, bedroom count, finished-basement status).

This guide is for informational purposes only and is not legal or tax advice. Deadlines, filing fees, success rates, and procedures vary by county within Illinois and can change year to year. Always verify the current rules with your local assessor's office — or a licensed attorney or tax professional — before filing. Source: Illinois Department of Revenue.

Appeal Deadline

30 days after the publication of the assessment list (varies by county, typically summer)

Appeal Body: County Board of Review

Step-by-Step Appeal Process

1
Review your assessment from the township assessor
2
File an appeal with the County Board of Review within 30 days of publication
3
Submit evidence: comparable sales, independent appraisal, or property data errors
4
Attend or submit a written appeal to the Board
5
If denied, appeal to the Illinois Property Tax Appeal Board (PTAB) or Circuit Court

Illinois-Specific Notes

Cook County (Chicago) has its own Board of Review with specific deadlines by township. Illinois assesses at 33.33% of fair market value.

Source: Illinois Department of Revenue

Assessment Savings Calculator

Estimate whether an appeal is financially worthwhile and your potential annual savings.

Current Assessed Value ($)

Estimated Market Value ($)

Effective Tax Rate (%)

Find your rate on your tax bill or the county website

Frequently Asked Questions

How do I appeal my property tax in Illinois?

File with the County Board of Review. 30 days after the publication of the assessment list (varies by county, typically summer). Start by requesting an informal review with your assessor, then follow the formal process outlined above if the issue is not resolved.

What is the Illinois property tax appeal deadline?

30 days after the publication of the assessment list (varies by county, typically summer). The typical deadline month is August. Always confirm the exact date with your local assessor's office, as deadlines can change year to year.

Do I need an attorney to appeal property taxes in Illinois?

No. Most homeowners successfully appeal without legal representation, especially at the initial administrative level. The process is designed to be accessible to ordinary homeowners.

What evidence is most effective for property tax appeals in Illinois?

Recent sales of comparable homes (3–5 "comps" from the last 6–12 months) that sold for less than your assessed value are the strongest evidence. An independent appraisal ($400–$800) is the gold standard. Property data errors (wrong square footage, extra rooms) are also persuasive.

Disclaimer: This guide is for informational purposes only and does not constitute legal or tax advice. Appeal deadlines, procedures, filing fees, and success rates vary by county within Illinois and change over time. Always verify current rules with your local assessor's office or a licensed attorney before filing. Success rates are estimates based on Lincoln Institute of Land Policy research and state-reported data — individual results vary.

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