Learn how to file for a Certificate of Error Online
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.
Homeowners can now apply for multiple exemptions and tax years using one consolidated form. Please carefully read through the eligibility and required document section of each exemption. Please note that Certificate of Error applications can be denied.
There are two types of Certificates of Error. One is for missing exemptions in past tax years and the other is to correct property-assessed valuations after a tax bill has been issued.
Missing Property Tax Exemptions? Homeowners can apply for Certificates of Error.
If a homeowner was eligible for a homestead exemption in tax years 2022, 2021, 2020, 2019, and 2018, and the exemption was not applied to the paid property tax bill, a refund can be obtained through the Certificate of Error process.
The property must have been eligible in the tax year in which a homeowner is applying. A photo ID along with other required supporting documentation must be supplied with the application to demonstrate eligibility. For example, to apply for a Homeowner Exemption Certificate of Error for Tax Year 2019, required documents must demonstrate that the home was the primary place of residence as of January 1, 2019.
Homeowner Exemption
File for a missing Homeowner Exemption
Apply online for tax years 2018, 2019, 2020, 2021, and 2022.
Senior Exemption
File for a missing Senior Exemption
Apply online for tax years 2018, 2019, 2020, 2021, and 2022.
Senior Freeze Exemption
File for a missing Low-Income Senior Citizens Assessment Freeze Exemption "Senior Freeze"
Apply online for tax years 2018, 2019, 2020, 2021, and 2022.
Persons with Disabilities Exemption
File for a missing Persons with Disabilities Exemption
Apply online for tax years 2018, 2019, 2020, 2021, and 2022.
Returning Veterans Exemption
File for a missing Returning Veterans Exemption
Apply online for tax years 2018, 2019, 2020, 2021, and 2022.
Veterans with Disabilities Exemption
File for a missing Veterans with Disabilities Exemption
Apply online for tax years 2018, 2019, 2020, 2021, and 2022.
Homeowner applies online.
Homeowner applies online.
The Assessor's Office processes Certificates of Error applications within 6-8 weeks.
The Assessor's Office processes Certificates of Error applications within 6-8 weeks.
Upon approval, the Treasurer's Office issues refund checks by mail within 3-4 weeks.
Upon approval, the Treasurer's Office issues refund checks by mail within 3-4 weeks.
What happens after I submit a Certificate of Error for a missing exemption?
During peak periods, it takes 6-8 weeks for the Assessor's Office staff to process an application. Next, the homeowner will receive a notification of
approval or denial. If an application is denied due to missing documentation, the homeowner may reapply with complete documents. If the application is approved, the homeowner will receive a mailed refund check from the Treasurer's Office within 3-4 weeks.
What happens after I submit a Certificate of Error for property-assessed valuation?
After a Certificate of Error application is received, it must be processed through the Assessor’s Office. If the property’s assessment has been previously reviewed by the Board of Review, the Board of Review must approve the Certificate of Error as well. In addition, 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 a Certificate of Error does not have to go to court for review, 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. 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 a Certificate of Error for assessed valuations only. This is not for exemption-related Certificate of Errors.
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 cannot 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.
Common Forms
Common Forms for Certificates of Error for Property Assessed Valuations
- Taxable Property Certificate of Error
- Tax-Exempt Property Certificate of Error
- Omitted Assessment Certificate of Error
Online filing is available if the Certificate of Error application is being submitted with a current year appeal.