Certificates of Error

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.

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If a homeowner was eligible for a homestead exemption in tax years 20212020, 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.

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Homeowner Exemption

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File for a missing Homeowner Exemption

Apply online for tax years 2018, 2019, 2020, and 2021. 

Apply Online 

Download Form

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Senior Exemption

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File for a missing Senior Exemption

Apply online for tax years 2018, 2019, 2020, and 2021. 

Apply Online 

Download Form

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Senior Freeze Exemption

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File for a missing Senior Freeze Exemption

Apply for tax years 2018, 2019, 2020, and 2021. 

Apply Online  

Download Form

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Persons with Disabilities Exemption

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File for a missing Persons with Disabilities Exemption

Apply online for tax years 2018, 2019, 2020, and 2021. 

APPLY ONLINE

DOWNLOAD FORM

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Returning Veterans Exemption

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File for a missing Returning Veterans Exemption

Apply online for tax years 2018, 2019, and 2020. 

APPLY ONLINE

DOWNLOAD FORM

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Veterans with Disabilities Exemption

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File for a missing Veterans with Disabilities Exemption

Apply online for tax years 2018, 2019, 2020, and 2021. 

APPLY ONLINE

DOWNLOAD FORM

Step 1

Homeowner applies online.

Step 2

The Assessor's Office processes Certificates of Error applications within 6-8 weeks. 

Step 3

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 which 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.

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Common Forms

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Common Forms for Certificates of Error for Property Assessed Valuations

Online filing is available if the Certificate of Error application is being submitted with a current year appeal.