Taxpayers of Cook County property taxes have been facing increasing pressure in recent years, thanks to rising property values and taxes. Illinois now has among the highest property taxes in the nation, and Cook County is a big reason why. Thanks to computer errors that have dragged on for years, property tax bills across the county are often late, inaccurate, or far larger than expected. The tax situation in Cook County has become so unpredictable that even the Chicago Bears are looking to move to Indiana to escape tax uncertainty.
One of the main tools that businesses and homeowners have to combat these rising costs is property tax appeals. While these have seen widespread use across Illinois, particularly in the collar counties, Cook County is the epicenter of their use. The deadlines for these appeals are separated by townships, with windows opening and closing at different times across Cook County. While the first round of appeals in many parts of Chicagoland has closed, the second round is quickly opening for many townships.
The Cook County Assessor Appeal
While the deck is often stacked against Cook County homeowners and businesses, the one saving grace is that the county has two official property tax appeal opportunities, compared with one in most other Illinois counties. The first appeal type is an assessor appeal, which is directly with the Cook County Assessor’s Office (CCAO). This is unique in Illinois, and often acts as the first chance to land a reduction or correction for taxes and values. While taxpayers in other counties can have informal meetings to request a reduction, only Cook has codified these into official hearings.
Many townships across the county have already seen these deadlines come and go in June and July. Once a notice of reassessment is published, there are 30 business days for the people of a township to file an assessor appeal. These deadlines are staggered out, allowing the CCAO to process each township. If a taxpayer files an appeal and it is either rejected or insufficient, then they can file a follow-up appeal when the opportunity arises. If a taxpayer missed the initial deadline, they may also file for this second round of appeals.
Cook County Board of Review Appeals
These secondary appeals are filed with the Board of Review (BOR), which is an impartial body that acts as a referee between the CCAO and the taxpayer. In the rest of Illinois, the BOR appeal is the only mechanism that taxpayers have. BOR appeals are slightly more complex than assessor appeals, though they require similar evidence. If a taxpayer has already gathered information, facts, and evidence for an assessor appeal, much of this will still be useful for the BOR hearing, though it is good to have it better organized.
In recent years, something of a rivalry has occurred between the BOR and the CCAO. Each organization has blamed the other for out-of-control property values. Because of this, the BOR has developed a reputation for being much more favorable to taxpayers than it is to the arguments of the CCAO. Whether this is true or not can be debated; however, the sheer volume of appeals to the BOR cannot be denied. In 2025, a record number of protests were filed with the BOR, even for townships outside of reassessment. 2026 appears likely to surpass those numbers, as both homeowners and businesses seek to correct errors and challenge property values.
Shorter Deadlines
While assessor appeals have a deadline of 30 business days, BOR appeals operate on a much tighter 30-day schedule, which can add pressure to an already stressful situation. These 30 days are not as spread out as assessor appeals, with the BOR holding hearings for multiple townships at once during the window. Because the window is much smaller, it can make the gathering of the necessary evidence much more difficult. With a bigger demand than ever for BOR hearings, it pays to prepare and file as early as possible.
The Last Chance for a Reduction
While assessor appeals are an optional step in the property tax reduction process, the BOR deadlines are not. If a taxpayer fails to file by the deadline, they lose the ability to protest for the entire year. There is no way to retroactively protest either, so it is imperative that every taxpayer file on time if they wish to challenge their values. While a rare third deadline was opened in December of 2025, such an occurrence is rare, which means taxpayers should act as if these upcoming deadlines are the last chance. While appeals can be later escalated to the Property Tax Appeal Board (PTAB), this can only be achieved if a BOR protest was filed first.
Townships with a BOR Deadline of September 1, 2026
Evidence Required by the BOR
We already have an article dedicated entirely to the evidence required for a successful BOR appeal, so we will do a brief overview. For a protest in Cook County to be successful, there must first be a valid ground for appeal. This is generally either overassessment or uniformity of assessment. Overassessment is when a property’s market value is much higher than what it would reasonably sell for on the open market. Unequal assessment occurs when a property is assessed at a higher value compared to neighboring properties .
Each ground for appeal has its own necessary evidence. For cases of overassessment, sales records dating back three years must be gathered to show the true market value for a property. For instances of lack of uniformity, assessments must be gathered from around the taxpayer’s home or business. These comparable properties, whether sales or assessments, must share as many commonalities as possible with the taxpayer’s property. These include size, location, age, the number of rooms, and other characteristics. This makes finding the right comparable properties the most important aspect of any BOR appeal.
O’Connor Gathers Key Evidence
Because of how specific the evidence needs to be for a successful BOR appeal, many taxpayers are defeated by the task of gathering facts and comparable properties. Many have compared gathering evidence in Cook County to having a second job. O’Connor is here to guide you in this process and will provide expert support for this most important part of the process. We have been helping clients across the nation for over 50 years and know the evidence needed for your case.
When you sign up with O’Connor, we will start by analyzing your assessment for any issues, mistakes, or incorrect values. This is done with data-driven techniques that we have refined over the decades. Then, we use our proprietary databases full of property sales, assessments, and more to identify the most appropriate comparable properties. These comparables will help tell the true story of your property, giving you a portfolio of evidence to prove your case. Finally, we will coordinate your appeal with a law firm that specializes in property tax law. You will not be charged upfront for these services, and will pay only a portion of your savings if your taxes are lowered.
