The Cook County Assessor's office and the Cook County Board of Review are open for a 30 day appeal period every year. Residents may appeal with both entities.

Most common grounds for an assessment appeal. There are three main types of appeals:

1. Lack of uniformity. Similar properties should be assessed similarly. To substantiate an appeal based on lack of uniformity, it is necessary to find properties comparable to yours that have lower assessed valuations. The Township Assessor's office can help you find comparable properties quickly and easily.

2. Errors in property characteristics. Every house has a set of characteristics which help determine its assessed value. Some characteristics errors can be used for an appeal. The type of characteristics errors most likely to result in an assessment reduction is one that overstates the square footage of your house. Only the Cook County Assessor can change property characteristics. Changes can only be made during our appeal period with the Cook County Assessor.

3. Recent purchase or appraisal. If the value set by the Cook County Assessor is higher than a recent purchase price or a recent appraisal for your property, you may use that as grounds for an appeal.

A successful appeal will typically remain in effect until the next reassessment.

You can check dates and deadlines for open appeal periods here:

Cook County Assessor

Cook County Board of Review