Why You’re Overpaying in Cook County

And How a Property Tax Appeal Can Help

If you live in Cook County, there’s a good chance you’re paying too much in property taxes. Many homeowners don’t realize that their property’s assessed value—the number used to calculate how much tax they owe—might be wrong. Even small mistakes can lead to hundreds or even thousands of dollars in extra taxes every year.

Luckily, there’s something you can do about it. This post will explain the most common assessment mistakes that lead to overpayment and how appealing your assessment can help you save money.

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What Is a Property Tax Assessment?

In Cook County, your property tax bill is based on the assessed value of your home. The county assessor estimates how much your property is worth, then uses that number to calculate your taxes.

But here’s the problem: those estimates are not always accurate. In fact, many assessments are based on incorrect or outdated information.

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Common Mistakes in Property Assessments

Below are some of the most common errors we see in property assessments:

1. Wrong Square Footage

If the county thinks your house is larger than it really is, your taxes will be higher. For example, if the assessor’s records say you have 2,000 square feet but your home is actually 1,600, you’re being taxed for space you don’t have.

2. Outdated or Incorrect Property Features

Sometimes, assessors include features that don’t exist—or no longer exist—like a finished basement, a garage, or an extra bathroom. They may also list the wrong exterior construction type, such as marking a home as masonry when it’s actually just frame. If these features are wrong in your file, you should update the Assessor.

3. Bad Comparable Sales (“Comps”)

The county often uses sales data from other homes in your area to decide what your home is worth. But if they use homes that are bigger, newer, or in better condition than yours, it can inflate your home’s value unfairly.

4. No Recent Updates to Reflect Changes

Did your home lose value due to damage, disrepair, or vacancy? If so, your property taxes should reflect that. But unless you file an appeal, the assessor won’t know to adjust your home’s value.

5. Mass Appraisal Errors

Cook County uses a mass appraisal system to assess thousands of homes at once. That means there’s no individual review of your property—mistakes are common. Thus, your neighbor can have a lower assessed value than you, and that is not fair. You should be able to tell the Assessor, “I want to have the same assessed value as my neighbor.”

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How an Appeal Can Fix the Problem

If you think your property has been over-assessed, you have the right to file an appeal. This process allows you to challenge the county’s valuation and provide proof of your home’s actual value.

Here’s how an appeal works:

1. Gather Evidence

Start by collecting documents that show your home’s true characteristics—like square footage, number of rooms, or recent appraisal reports. You can also find sales data for homes like yours (called “comps”) that sold for less or or received lower assessments. This should include finding your neighbor’s and surrounding neighbors’ assessed values from homes that are similar to yours.

2. File With the Assessor or Board of Review

You can file an appeal through the Cook County Assessor’s Office or the Cook County Board of Review. Each has its own deadlines and forms, so timing is important.

3. Present Your Case

You’ll submit your evidence and make a case for a lower assessed value. If your appeal is successful, your assessed value will go down, and you will pay lower taxes than if you the assessed value stayed the same

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Why Hire a Property Tax Attorney?

While you can file an appeal on your own, many people choose to hire a lawyer to help. A qualified attorney understands the appeal process and knows how to find the strongest evidence to support your claim. At Aaron Fox Law, we help clients across Chicago and Cook County lower their property taxes through targeted appeals.

We know what assessors look for, and we’ve helped many homeowners and commercial property owners reduce their tax burden. You don’t need to handle this alone.

If you think your property taxes are too high, speak with a trusted Cook County property tax Attorney to review your case.

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Don’t Wait—Appeal Deadlines Matter

Each township in Cook County has a short window when appeals are allowed—usually just 45 days for assessor and 30 days for BOR. If you miss the deadline, you’ll be stuck with your current tax bill until next year. That’s why it’s important to act fast if you suspect an error.

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Conclusion

Paying property taxes is part of owning a home—but overpaying doesn’t have to be. Many Cook County residents are taxed based on incorrect information about their homes. Whether it’s wrong square footage, outdated data, or bad comps, these mistakes can cost you big time.

Filing a property tax appeal gives you the chance to correct the record and lower your tax bill. And with the help of an experienced attorney, the process can be faster, easier, and more successful.

Think you’re overpaying? You might be. Reach out today to learn how Aaron Fox Law can help you take the next step toward a fairer property tax bill.