Illinois law provides the Certificate of Error procedure to allow the Cook County Assessor to apply changes to a property tax bill that has already been issued. It is a way to make a correction after the assessment for that tax year is finalized. This page explains the process of correcting a property's assessed valuation after a tax bill has been issued.
There are two types of Certificates of Error.
- One is for missing exemptions for past tax years.
- The other is to correct a property's assessed valuation after a tax bill has been issued.
How to apply for a Certificate of Error
When to apply for a Certificate of Error
There are two ways to file a Certificate of Error.
- You can file online with an appeal filing for the
How does the approval process work?
After a Certificate of Error application is received, it must be processed by the Assessor’s Office. If the property’s assessment has been previously reviewed by the Cook County Board of Review, they must also review and approve the Certificate of Error. Lastly, you will receive a letter from the Assessor’s Office that indicates whether the Certificate of Error has been granted or denied.
Certificate of Error applications can be denied. You can review the Certificate of Error Denial Reason Codes.
Certificate of Error applications for non-residential properties that seek a reduction of more than $100,000 in assessed value must be sent to the Circuit Court for a judge’s consideration. If the Certificate of Error is required to go to court for adjudication, a letter regarding the outcome of that Certificate of Error request will be sent to you by the Cook County State's Attorney’s Office.
How to look up the status of your Certificate of Error
The Certificate of Error Status Search, also known as the “Tracker”, is a quick way to find the status of most types of Certificates of Errors for assessed valuations. This tool is not for exemption-related Certificate of Errors.
The following types of Certificates of Errors can be found using the Tracker.
• Valuation based, including those issued to activate incentives or class changes.
• Those based on Homestead exemptions.
• Those based on non-homestead exemptions.
Please note that Certificates of Errors which are submitted either by paper or via email will not appear on the Tracker until the Certificates of Error have been entered into the Assessor’s system of record.
The following types of Certificates of Errors can not be found using the Tracker.
• Omitted Assessments
• Farmland-related Certificates of Errors
If you have questions, contact the Taxpayer Resolution Department at Assessor.Taxpayer.Resolution@cookcountyil.gov.
- How long does it take for an application to be reviewed and approved?
- When can I file a Certificate of Error?
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- How do I know which township my property is located?
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- Why does the Board of Review have to approve the Certificate of Error?
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