How does Cook County's triennial reassessment schedule work, and is my area being reassessed this year?

Cook County uses a triennial reassessment cycle: each property is reassessed once every three years rather than annually. The Cook County Assessor's office alternates reassessments across three groups of townships — the City of Chicago, the north and west suburbs, and the south and west suburbs — so one of the three is reassessed each year. See Learn about Reassessments and Your Assessment Notice and Tax Bill.

2026 reassessment group. In 2026 the south and west suburbs are being reassessed. Property owners in that group will be mailed a Reassessment Notice — containing the property address, characteristics, and updated estimated fair market value — beginning in late April 2026. Properties in the City of Chicago and the north suburbs are not on the regular 2026 reassessment, and are only reassessed mid-cycle if there is a change due to division work, permit applications, or other special circumstances.

Why the reassessment year matters for appeals. Your strongest, simplest time to appeal is the year your township is reassessed, because that is when the Assessor sets a fresh value and mails a notice that opens your appeal window. The Assessor notes that once you successfully appeal in a reassessment year, you generally "do not need to do it each year, unless the characteristics of your property have changed significantly."

You can still appeal in off years. Even when your area is not being reassessed, you may file an appeal during your township's annual window if you believe the value is too high — for example, if comparable homes are assessed lower or the record overstates your square footage. Check your township's reassessment status and current appeal window on the Assessment & Appeal Calendar.