How Cook County property tax appeal deadlines work
Cook County does not use one countywide appeal deadline. Each township has its own Assessor window and, later, its own Board of Review window.
Search the property first, then confirm its township deadline.
Enter a Cook County address or 14-digit PIN to see the property and comparable evidence before you spend time preparing the filing.
Free to check first. No credit card required.
Current-year analysis is shown only when the active Cook County data snapshot supports the property. The property search is the availability check.
Assessor windows open now
These township Assessor windows are open in the current 2026 calendar. Preserve the Assessor opportunity first if you want both review stages.
Board of Review windows open now
The Board is the second independent review stage. These published formal Board filing windows are open now.
Board pre-file is available for not-yet-open townships
The Board's current 2026 guidance allows homeowners to pre-file or preregister when their township has not yet opened formally. This is different from a township whose formal Board window has already closed.
11 townships currently show Board pre-file as their next actionable status in this guide.
The two deadlines are separate
First review opportunity.
Second, independent review opportunity.
Township-specific opening and last-file date.
Separate township window published by the Board; pre-registration may open earlier.
A Board filing does not restore the missed Assessor opportunity.
If a formal Board window is not listed yet, pre-file/preregistration may be available; confirm on the Board site.
Where to verify today's deadline
Use the official County calendars before filing. The Assessor publishes reassessment notice dates and Assessor filing deadlines. The Board publishes its own current township dates and deadlines.
Why a reassessment notice matters
When a township is reassessed, the notice is the homeowner's trigger to inspect the new valuation and decide whether to appeal. Cook County's 2026 calendar says the south and west suburbs are the scheduled reassessment area this year.
See 2026 reassessment guidance and current township guides →Check your property while its current assessment data and filing window are actionable.
Status uses the Chicago/Central calendar date. Deadline information can change; official Cook County calendars and filing systems control.