How to Protest Property Taxes in Cook County

Two stages, separate offices

The Cook County Assessor's Office sets the assessed value. The Cook County Board of Review is a separate office that reviews assessments independently after the Assessor has valued the property. An appeal to the Assessor does not decide the Board of Review appeal, and a Board of Review appeal does not require an Assessor appeal first.

Cook County reassesses one-third of the county each year on a triennial cycle, but an appeal window opens for your township each year whether or not your township was reassessed that year. The window is set township by township. The Assessor's Office states that appeals may only be filed during certain periods and directs filers to check the Appeals Calendar and Deadlines page to see if their township is open.

Stage 1: appeal to the Assessor's Office

File online when your township is open. The Assessor's Office encourages online filing and states that paper appeal forms are available for filers who cannot file online. The Assessor's Residential Appeals page states that any data and documentation supporting the appeal must be submitted concurrently with the appeal, and that online filing is strongly recommended for timely processing.

The last date to file an appeal is printed on your notice. The Assessor's Office states that typically you have 30 days to file an appeal after receiving your reassessment notice. Do not treat 30 days as a fixed county-wide date: the printed date on your notice controls.

The common grounds the Assessor's Office names are uniformity, overvaluation, and incorrect information. For uniformity, compare your assessed value with comparable properties in your assessment neighborhood: similar classification, building age, square footage, land square footage, and exterior construction. For overvaluation, the Assessor's Office encourages supporting documentation such as recent closing statements or purchase prices of similar homes. For incorrect information, such as incorrect square footage, submit supporting documentation with the appeal. Dated photos, a property deed, or other evidence listed in rules 13 through 24 of the Assessor's Official Appeal Rules can support the appeal. Any appraisal submitted with an appeal must be USPAP compliant.

You do not need to file a list of comparable properties with your appeal. The Assessor's Office states that its analysts will review other comparable properties and decide whether your assessed value is accurate based on homes similar to yours.

Stage 2: appeal to the Board of Review

The Board of Review opens townships in groups and publishes an opening date and a closing date for each group. For the third group of the 2026 season (Lyons, Northfield, Stickney, and West Chicago townships), the Board stated the group would open for filing on Thursday, October 8, 2026, and close on Friday, November 6, 2026. Those dates apply only to that group and that year. Check the Board's current calendar for your township.

Appeals may be filed online at the Board of Review website, through an attorney or authorized tax representative, or in person at the Board office, 118 N Clark St., Chicago, IL 60602, Monday through Friday from 9 a.m. to 5 p.m. There is no fee to file an appeal. The Board also runs a pre-file period for non-attorneys that allows filers to submit an appeal before their township officially opens; the pre-file period for a township ends once that township opens.

The Board states that all 38 townships in Cook County will have an opportunity to file in the 2026 season. If your township's filing period has closed, the Assessor's Office states you may appeal the following year when your township is open for appeals.

What this guide does not state

No Board of Review evidence deadline is stated here. No general Board filing-window length is stated as a Board rule, because the Board pages opened for this guide state group opening and closing dates, not a general day count. No Property Tax Appeal Board (PTAB) deadline or procedure is stated, because no PTAB primary page was opened for this guide. No filing fee is stated beyond "no fee," and no decision timeline is stated for either stage, because neither was verified on the primary pages opened.

For property tax protests in other counties, see the Property Tax Appeal by County directory. To check a deadline from a notice date, use the Property Tax Protest Deadline Checker.

Source

Sources: Cook County Assessor's Office, Residential Appeals page (cookcountyassessoril.gov); Cook County Board of Review, press release opening the third group of townships for the 2026 appeal season (cookcountyboardofreview.com). Facts verified 2026-11-03.

This page explains how the process works and what the official rules say. It is general information, not legal advice. For a dispute about your specific situation, talk to the Cook County Assessor's Office or the Cook County Board of Review.