Tax Extension and Rates

The Clerk's Tax Extension Unit is responsible for calculating property tax rates for all local governments, or taxing districts, in Cook County that authorize the collection of revenue through real estate taxes.

How tax rates are calculated:

• The Cook County Assessor's office establishes property valuations.
• Taxing districts file their levy requests with the Clerk's Tax Extension Unit.
• To produce the revenue requested, the Tax Extension Unit uses the levy to determine the tax amount to be "extended" against all properties located within the boundaries of the taxing district.
• The Clerk's Tax Extension Unit determines the rate needed per $100 of taxable value to generate the requested revenue, based on the value of all taxable property within the district boundaries

(Note: Limits under Illinois law can restrict the revenue, either through statutory maximum rates for certain purposes and/or through "tax caps," which limit the total amount extended. Extension limits are not applied to funds needed to pay bonds and certain other charges.)

Interactive Tax Reports (Query by District, Year & Report type):

Tax Reports Available Online:

Cook County Annual Tax Rate Report

Cook County Tax Code Rate Summary (10-year report)

Cook County Agency EAV and Extension by Class