Cook County, IL Property Tax Appeal Deadline 2026

Cook County hears residential appeals township by township — when your township opens, you generally have about 30 days to file (35 ILCS 200/16-55), and the Cook County Board of Review publishes each township's open and close dates. That rolling calendar means the right moment to act is when your reassessment notice arrives, not a fixed date.

Filing with the Cook County Board of Review is free, and uniformity — showing your assessment is out of line with comparable homes around Chicago, Evanston and Schaumburg — is a recognized ground in Illinois. The proof standard is real, though: a persuasive uniformity case takes genuinely comparable properties, not a single raw price-per-square-foot number.

• Property owned by a corporation or LLC must be appealed by an attorney in Illinois — the self-service route below is for individually owned homes.

How to appeal in Cook County — step by step

1. 1

   Find your township's schedule

   Look up your township's open and close dates on the Cook County Board of Review's calendar — the window is roughly 30 days from opening, and it's your real deadline.

2. 2

   Build your comparables

   Identify genuinely similar homes (neighborhood, size, age, construction) and compare their assessments against yours. The stronger and more similar the set, the better — Illinois uniformity review expects more than one loose comparison.

3. 3

   File with the Board of Review

   Submit your appeal — online portal, mail, or in person — before your township closes. Fee: $0 — no filing fee.

4. 4

   Submit complete, signed paperwork with all evidence

   Incomplete or unsigned filings get returned, and at the state Property Tax Appeal Board (if you later escalate) all evidence must accompany the petition — build the full packet up front.

5. 5

   Keep paying your tax bill

   An appeal does not pause collection. Pay on time; a reduction flows through after the decision.

Frequently asked questions

• When is the deadline to appeal property taxes in Cook County in 2026?

  Cook County has no single 2026 deadline — appeals open township by township, and you generally have about 30 days from your township's opening to file (35 ILCS 200/16-55). The Cook County Board of Review posts each township's open and close dates; your township's schedule controls.

• What does it cost to file?

  Nothing — Cook County Board of Review appeals are free.

• Do I need a lawyer?

  Individual homeowners can file and argue their own appeals. Property owned by a corporation or LLC is different — Illinois requires those appeals to be filed by an attorney.

• What if my township already closed?

  Once your township's Board of Review window closes, the next regular chance is the next appeal cycle — watch for your reassessment notice and your township's opening date next time, and calendar it as soon as it's posted.