Wrong square footage on your Cook County assessment?

1. Find the county’s property record

Look up your address or 14-digit PIN on the Cook County Assessor's website. Confirm that the result is your property, then save the record and note the assessment year and the date you accessed it. Our PIN lookup guide can help if the address search is ambiguous.

Review building area, land area, property class, age, and other listed features. Use your assessment notice alongside the online record. If the two disagree, keep both versions and ask which one applies to the year you are reviewing.

2. Compare building area with building area

Land square footage describes the site. Building square footage describes an area of the structure. These figures are not interchangeable. A survey showing the lot boundary does not, by itself, settle the measured area of every floor.

Before comparing a county entry with an appraisal, floor plan, or sale listing, read the labels and measurement notes. Check whether each source includes the same floors and spaces. Ask about basements, attics, garages, additions, or enclosed porches when the records are unclear; do not assume every source uses the same definition.

A difference between two records is a question to resolve. It is not enough to choose the smaller number because it might support a lower assessment.

3. Document the exact discrepancy

Prepare a short note with three parts: the county entry, your proposed correction, and the document supporting it. For example: “The record lists [area]. I request review because [dated document] shows [area] using [measurement description].” Fill in only facts you can support.

Depending on the issue, useful records to discuss with the county may include measured floor plans, an appraisal with a building sketch, or documentation of an addition or demolition. Photographs can help explain a physical feature, but an exterior photo alone does not measure the whole building. Ask the office what documentation is appropriate for your request.

Keep copies of what you submit. Identify any uncertainty instead of presenting an unsupported estimate as an established measurement.

4. Request a factual correction or prepare an appeal

The Assessor's Rule 25 provides methods for requesting factual corrections, including the contact page, email, mail, and in-person assistance. SmartFile also supports residential characteristic updates during an appeal. Use the current rule to choose a method and include supporting evidence.

A factual correction addresses a record entry. A valuation appeal challenges the assessed value. Explain both issues separately if both apply. Save the submission confirmation and any instructions for following up.

If you are filing an appeal, verify your township's current window and document deadline. A contact message is not a substitute for a timely appeal filing. Our township pages link to official calendars.

5. What if the appeal deadline has passed?

Rule 25 encourages reporting factual errors even outside the current-year appeal process. Ask the Assessor which correction procedure applies to your property and year. For a prior-year valuation issue, ask whether the Certificate of Error process is appropriate and what its current requirements are.

This does not reopen an appeal window or guarantee a refund. Our missed-deadline guide explains other calendar checks. You can also get free township deadline alerts while gathering records.

6. Property-record correction checklist

7. Will correcting square footage lower my taxes?

Not necessarily. Rule 25 says many characteristic changes do not change valuation. An area correction is not a proportional tax-bill reduction.

Once you have checked the property facts, you can investigate whether nearby recorded sales support the county's estimated value. Our free property check helps with that sales research. It does not measure your home, change the county's records, or file a correction request.