With the exception of Class 2 residential properties for which separate rules have been issued, the Office of the Assessor has prepared these rules to assist all Cook County property owners in pursuit of any claim of over-assessment.

Illinois law requires the Assessor to place an assessed valuation on all real property located in the county. The law also gives property owners the right to challenge the values set by the Assessor. Under the law, property owners must submit evidence sufficient to justify a reduction in assessed valuation.

It is the policy of the Cook County Assessor to assess all real property in a fair and uniform manner consistent with the legal responsibility placed on the Office of the Assessor. It is also our policy to provide everyone equal access to the remedies afforded by the appeal process. In accordance with these policies, the Office of the Assessor shall provide experienced personnel to assist property owners who want to appeal their assessed valuation.

Residential property owners who experience severe damage to their homes as a result of a catastrophic event are eligible to receive a home improvement exemption of up to $75,000.

This exemption is available when a residential structure is rebuilt after a catastrophic event. The exemption applies to the difference between the increased value of the rebuilt structure and the value of the structure before the catastrophic event.

A Real Estate Certificate of Error (C of E) allows the Cook County Assessor to change a property’s assessed value. Illinois law provides this procedure as a way to correct a tax bill after the assessment for that tax year is finalized. A Certificate of Error addresses a single year. If you are entitled to a value reduction for more than one year, a Certificate of Error request must be filed for each individual year.

You may a request for a re-review. Get the form here.If you wish to appeal your assessment further, you may also file an appeal with the Cook County Board of Review (312-603-5542).

To file an appeal now, use the Property Searchon this Web site and click on Appeals. Once there, complete the information and file the appeal. If you do not see a form at this point then that means your township is not open to submit appeals. You may also file an appeal at our office, your local township office, or you may request that an appeal form be mailed to you. Experienced personnel are available at all of our offices to help you in filing your appeal.

A “comparable property” is a property located within your assessment neighborhood which has characteristics similar to those of your property. These characteristics may include property classification, building age, building square footage, land square footage, and exterior construction. A complete list of your property's characteristics can be found in the “property characteristics” section when your PIN number is entered.

Three common grounds for appeals are listed below:

1. Uniformity Appeal:

   If you are concerned that the assessed valuation of your home is not uniform with the assessed valuations of other similar homes, compare your property to similar homes. This comparison will help you determine if you have reason to file a uniformity appeal.

   There are two ways to do this:

Appeals can be filed when your township is open for appeals. To file an appeal online, find your property via our Property Search. If you cannot file an appeal online, prefer to visit one of our offices, or want to mail your appeal, you must use an official "Real Estate Assessed Valuation Appeal" form. Please submit one copy and keep another copy for your files. You do not need a lawyer, tax representative or appraiser to file an appeal on the assessed valuation of your home.

You will receive a reassessment notice in the mail when the Assessor's Office reassesses your home every three years. This notice contains a proposed assessment which will be reflected on your subsequent year’s second-installment tax bill. It also contains our data about your property's characteristics, like its square footage. For residential homes, we use these characteristics to produce your property value.