Cook County property tax appeal after buying a home

1. Is your assessment higher than your purchase price?

Find your PIN and assessment year on the notice. Then find the county's estimated market value. Compare your purchase price with that figure, keeping the sale date beside it. Our assessment notice guide explains the difference between market value and assessed value.

Write down the question you want the records to answer: “Does this sale support a lower market value for the assessment year?” Keep the full notice with your closing papers so you can check both dates and figures later.

2. Why can the county's value differ from your closing price?

The Assessor's appeal overview explains that a recent purchase price does not always equal market value. The buyer, seller, and timing of the transaction can affect the price.

Make a short timeline: when the home was listed, when you signed the contract, when it closed, and any major work completed afterward. Note any relationship with the seller, unusual sale terms, or condition problems. Keep documents that support those details rather than guessing at their effect on value.

A family transfer, a distressed sale, or a home renovated after closing needs context. Describe what happened plainly. Do not treat every recorded transfer as the same kind of market evidence.

3. Which purchase documents do you need for an appeal?

For an Assessor appeal, start with the current official appeal rules, especially Rules 12 and 13. The 2026 rules require disclosure of a purchase or sale within two years of January 1 of the appeal year, even when you are appealing for another reason or the transaction was not at arm's length.

Use these rules to build your document checklist:

• The sale price and date, plus the relevant signed contract, deed, and closing statement.
• The buyer and seller identities and any relationship between them.
• A property photograph that meets the current rules.
• The PTAX-203 transfer declaration, which the Assessor strongly encourages for purchase-price arguments.

A substantial difference between the sale price and the county's valuation requires an affidavit explaining the sale circumstances. Special transactions can require additional records. Read the full rules for your facts and filing year; this checklist is a starting point.

4. Check the property facts and nearby sales

Review the county's description of your home. If you find a possible error, write down the county entry, the correction you believe is needed, and the record that supports it. Keep this separate from your purchase-price comparison.

Then look at similar recorded sales. For each candidate, note its date, price, size, age, property type, and important differences from your home. Do the comparisons tell a consistent story, or do some point the other way? Save both kinds of findings.

A free Check the County home check can help you review nearby sales. It does not review your closing documents or submit them to the county. Keep your purchase evidence in your own filing folder.

5. Confirm where and when you can file

Check your township on the official Assessor calendar. If you are considering the Board of Review, use its official website to check its own schedule and rules. Our appeal office comparison explains the two paths.

Keep a folder with your notice, sale records, comparison notes, and a short explanation of what you are asking the office to review. Before submitting, check the receiving office's current document requirements and save the filing confirmation. If the window has closed, read our missed-deadline guide.

6. Will a lower assessment mean the same cut in taxes?

The Assessor's appeal overview explains that a percentage change in an assessment does not produce the same percentage change in taxes. Exemptions and local levies also affect the bill. Avoid turning a purchase-price gap into a promised dollar saving.

Filing directly with the Assessor is free. Check the County charges only for optional organized research; buying research is not required to file. For separate questions about exemptions after buying a home, see our exemption guide.