Cook County property tax appeal timeline.

Start with the township and notice

The Cook County Assessor calendar says Cook County follows a triennial reassessment cycle and that a property's reassessment year depends on the township. The same page lists township mailing dates, last-file dates, certification dates, publication dates, and Board of Review appeal dates when those dates are posted.

When checked on June 20, 2026, the Assessor calendar still displayed a 2025 assessment calendar and the Board dates page linked Tax Year 2025 township materials. Treat those pages as official mechanics and source links, not as a substitute for confirming your live township status.

Prepare evidence before the Assessor filing

The Assessor says a homeowner typically has about 30 days after receiving a reassessment notice, and the last date is printed on the notice. The online appeal page also warns that starting a file before the township is open may result in a deleted file.

Do not wait until after submitting to build the file. Cook County residential appeal guidance says supporting data and documentation must be submitted concurrently with the appeal.

Assessor decision timing is mailed, not guaranteed here

After online filing, the Assessor says filers receive confirmation and a docket number by email, and that appeal results are sent by mail. The public workflow checked for this page did not provide a guaranteed number of days for a residential decision.

Use the docket number, mailed result, property record, and township certification status as the practical checkpoints. If timing matters for a Board complaint, verify the Board window separately instead of assuming the Assessor result controls every later deadline.

Board of Review is a separate stage

The Board FAQ describes the Board as a separate, quasi-judicial agency independent of the Assessor. The Board opens townships after Assessor assessment, says township dates vary annually, and says all townships are open for at least 30 days.

The Board rules say the complaint must be filed by the official township closing date and late evidence will not be accepted except in narrow Board-requested situations. The Board's Tax Year 2025 materials also publish township-specific evidence deadlines, hearing periods, decision dates, and re-review windows.

After the Board, choose the next path quickly

The Board FAQ says that after first appealing to the Board, a taxpayer may choose to appeal further to the Cook County Circuit Court or the Illinois Property Tax Appeal Board. Illinois Department of Revenue guidance similarly says a written Board appeal is a prerequisite to further appeal to PTAB or circuit court.

PTAB says a petition must be filed within 30 days of the postmark date of the Board decision notice or the notice of final adopted township multipliers. IDOR also warns that taxes must be paid pending the outcome of a PTAB appeal or circuit court tax objection.

Exemptions and Certificates of Error are side paths

A high bill is not always an assessment appeal problem. The Assessor says a Certificate of Error can correct a bill that has already issued, including missing homestead exemptions for eligible prior years and some valuation issues.

Keep the side path separate in your timeline. Missing exemptions need eligibility documents by tax year, while valuation Certificates of Error may have uncertain processing timing and can be affected by whether the same tax year is pending at PTAB or circuit court.

FAQ