The Cook County's Assessor's Office is responsible for determining the current value of nearly 2 million properties in Cook County.
Illinois law requires that local governments periodically update the property values across a region for real estate tax purposes.
Cook County is divided into 36 areas called townships spread across three regions: the northern suburbs, southern suburbs, and the City of Chicago. Each of these regions is valued once every three years.
When properties are scheduled for reassessment the last three to five years of sales information from the area you live in. for that community area. Using multiple sale years increases the stability of our market value estimates.
Finding Property Values Through Mass Appraisal
The Cook County Assessor's Office uses a process called mass appraisal to determine property values. Instead of appraising properties one-by-one, we use data and trends from the local real estate market based on location and property characteristics. These trends are then used to produce an estimated fair market value for each property being assessed.
By looking at the overall trends in the real estate market, mass appraisal allows us to fairly assess all the properties we evaluate.
Understanding Fair Market Value and Assessed Value
We use two key values when assessing your property. We use fair market value to calculate what the fair cash value would be for your property if it had sold in its most recent reassessment year. Assessed value refers to a percentage (%) of the fair market value that we base property taxes on.
Learn how different types of property are valued and how assessments fit into the overall property tax system of Cook County with the links below.
Appealing Your Assessment
We update each property’s fair market value and related assessed value once every three years.
Property owners have a right to file an appeal if they believe their property’s assessment is incorrect. When filing an appeal, know that
- There is no fee
- You do not need to hire an attorney or tax representative
If you want to file an appeal with us at the Assessor's Office, you must do so by the date noted on your reassessment notice. If that date has passed, you have an additional opportunity to file an appeal with the Cook County Board of Review.
Please read the general information about appeals for important information about rules for filing and deadlines for your area.
We have staff and resources available to help you file appeals through our Taxpayer Services Department. In the suburbs, assistance is also available from the local township assessor.