What evidence supports a Cook County property tax appeal?
The best evidence depends on why the assessment is wrong. A clean residential appeal usually fits one or more of three lanes: lack of uniformity, overvaluation, or incorrect property characteristics.
Start with the public record and comparable-property evidence.
Enter a Cook County address or property PIN.
Free to check first. No credit card required.
Similar homes are assessed lower
- Comparable PINs
- Physical characteristics
- Current assessments
- Assessment-per-square-foot comparison
The estimated market value is too high
- Recent arm's-length purchase
- Appraisal or credible market evidence
- Recent comparable sales when appropriate
The property facts are wrong
- Photos
- Survey or plans
- Property record evidence
- Other documentation supporting the correction
A long list of weak comps is not stronger evidence
For a uniformity case, a compact set of physically credible properties is more useful than a large dump of nearby parcels. The Assessor's rules require at least three comparable properties for a comps-based filing and recommend at least five.
Always include the identifying details
Comparable-property evidence should be verifiable. Keep the address, PIN, assessment values, and the characteristics that make each property genuinely comparable. Verify the final evidence against the official County record before submitting it.
How to choose strong Cook County comparables →Use the evidence at the correct stage
The Assessor and Board of Review are separate filing opportunities. The same core property facts can support both, but the portals, deadlines, and submission mechanics differ.
Assessor vs. Board of Review →Official evidence guidance
See whether your property has a coherent comparable-evidence case.
Evidence requirements vary by appeal basis and property type. Confirm current official filing rules before submission.