The homeowner's reading room
How to read your Cook County assessment notice
Before deciding whether to appeal, make sure you are reading the right property, year, and kind of value. Use this walkthrough with your notice beside you.
1. Confirm the PIN and assessment year
The Assessor's notice explanation describes the property identifier, characteristics, values, and exemption history shown on the document. Begin with the PIN and year rather than the largest dollar figure.
Match the PIN to your property record. Keep all 14 digits, including leading zeros. If you need help locating it, use our PIN lookup guide. Put the notice date and assessment year at the top of your notes so that later comparisons stay in the same period.
2. Distinguish market value from assessed value
For residential properties, the Assessor states that assessed value is 10% of estimated fair market value. Its residential valuation explanation describes how property characteristics and nearby sales inform the estimate.
- County estimated market value
- $400,000
- Residential assessment level
- 10%
- Assessed value
- $40,000
The $40,000 is not a $40,000 tax bill. And the $400,000 is the county's estimate, not a guaranteed selling price.
Label each value you write down. When comparing a sale price with the notice, compare it with the estimated market value, not directly with the assessed value. An assessed-value-per-square-foot comparison is a different analysis from a sale-price-per-square-foot comparison.
3. Check the facts used to describe your home
Review the property type, building area, age, and other listed characteristics against records you can support. Keep a simple three-column note: county entry, what you believe is correct, and supporting document. For example, record a suspected area discrepancy with the source of the measurement rather than an unsupported estimate.
The Assessor's current appeal rules require filers to review the property details and explain inaccuracies with supporting information. They also describe a SmartFile function for updating residential characteristics. Follow the instructions for the type of request you are making.
A corrected fact is useful evidence, but it does not by itself tell you the eventual value. Keep the factual correction separate from your explanation of why the assessment should change.
4. Record the deadline before gathering evidence
Check the date on the notice against the official township calendar. The calendar lists assessment and appeal timing by township. Do not substitute a tax payment due date for an appeal deadline.
Save a copy of the notice, your notes, and any evidence in one folder. Add a calendar reminder ahead of the deadline so you have time to review the receiving office's document requirements. The Assessor's current rules require supporting documents by the appeal deadline.
If the date has already passed, our missed-deadline guide explains which schedules and correction resources to check next.
5. Turn the notice into a research question
Finish with a specific question: “Are these property facts correct?” or “Do similar recorded sales support this estimated market value?” A precise question makes the next step more useful than simply collecting the lowest prices you can find.
Start with our comparable-sales guide, or run a free property check below. Keep differences between properties visible in your notes; evidence is stronger when you can explain both the similarities and the limitations.