If you own property in Cook County, you are almost certainly paying too much in property taxes. That's not a hot take — it's just how the system works until you push back. The good news is that the appeal process is free, online, and doesn't require a lawyer. The bad news is that nobody tells you that until you've already paid the bill. Here's exactly how the property tax appeal process works in Cook County, step by step, so you can stop donating money to the void.
How Cook County Property Tax Assessments Work
Before you can appeal, it helps to understand what you're appealing. Cook County operates on a triennial reassessment cycle, meaning your property gets reassessed every three years depending on which region you're in. The county is divided into three sections — north suburbs, south and west suburbs, and the City of Chicago — and each section is reassessed on a rotating schedule. For 2026, the south and west suburban townships are up for reassessment. That includes Berwyn, Bloom, Bremen, Calumet, Cicero, Lemont, Lyons, Oak Park, Orland, Palos, Proviso, Rich, Riverside, Stickney, Thornton, and Worth. If your township is on this list, expect a reassessment notice sometime between March and May 2026. The Cook County Assessor's Office determines the assessed value of your property based on recent sales data, property characteristics, and local market conditions. Your property tax bill is then calculated using that assessed value. If the assessed value is too high, your tax bill is too high — and in a county where tax rates swing wildly by suburb, that gap compounds every year. That's where appeals come in.
Step-by-Step: How to File a Property Tax Appeal in Cook County
There are two main levels of appeal in Cook County, and you can file both — in order — for free.
Level 1: Appeal to the Cook County Assessor
When to file: You have 30 days from the date your reassessment notice is mailed to file an appeal with the Assessor's Office.
How to file: Go to cookcountyassessoril.gov/online-appeals. You'll need an email address to create an account. The whole process can be done online in about 20 minutes.
What to submit: You can submit comparable property data, a recent appraisal, or evidence that your property's characteristics are inaccurate (wrong square footage, lot size, etc.).
How long it takes: The Assessor typically renders a decision within 60 to 90 days of your filing. You do not need to hire anyone to file. The Assessor's Office makes this very clear. Those letters you get from tax appeal firms are not from the county — they're from private companies that charge a percentage of any savings. You can do the same thing yourself for free.
Level 2: Appeal to the Board of Review
If you're not satisfied with the Assessor's decision — or you just want a second shot — you can file another appeal with the Cook County Board of Review.
When to file: The Board of Review opens each township for appeals on a rolling schedule after the Assessor has finished. Check cookcountyboardofreview.com/dates-and-deadlines for your township's window.
How to file: Visit appeals.cookcountyboardofreview.com to file online or pre-register if your township hasn't opened yet.
How long it takes: The Board generally takes 90 to 120 days to conduct hearings and issue decisions. One critical detail: the Board of Review can never increase your assessed value. They can only maintain it or reduce it. So there is literally no downside to filing.
What Happens After the Board of Review
If the Board of Review still doesn't give you the reduction you think you deserve, you have one more option. You can appeal to either:
The Property Tax Appeal Board (PTAB) — a state-level body that reviews Cook County decisions independently.
The Circuit Court of Cook County — a formal legal proceeding. In both cases, you must file within 30 days of the Board of Review's written decision. Miss that window and you're done until the next assessment cycle. Most homeowners won't need to go past the Board of Review. But it's good to know the option exists. If you're a first-time buyer still sorting out what Illinois actually charges you to own property, state and local buyer assistance programs are worth exploring before your next bill drops.
What Evidence Do You Need for a Strong Appeal
You don't need a law degree, but you do need actual evidence. The most common — and most effective — approach for residential appeals is comparable sales data. Here's what to gather:
Comparable properties ("comps"): Find 3 to 5 recently sold properties in your area that are similar in size, age, and condition but sold for less than your assessed value implies. The Assessor's website has a tool for this.
Property description errors: Check your Property Index Number (PIN) details on the Assessor's site. If they have the wrong square footage, number of bedrooms, or lot size, that's immediate grounds for a correction.
Recent appraisal: If you recently had your home appraised for a refinance or sale, and the appraised value is lower than your assessed value, submit it.
Photos of property condition: If your property has significant deferred maintenance, damage, or other issues that affect its value, document it. All documentation must be legible, complete, and have non-public personal information redacted before submission. The Assessor's Office provides official forms at cookcountyassessoril.gov/forms.
Key Deadlines and Resources for 2026
If you're in one of the south and west suburban townships being reassessed in 2026, your timeline looks roughly like this:
March–May 2026: Reassessment notices mailed
30 days from your notice: Deadline to appeal to the Assessor
Fall 2026: Board of Review opens townships for second-level appeals
30 days from Board of Review decision: Deadline to appeal to PTAB or Circuit Court Bookmark these resources:
Cook County Assessor's Office: cookcountyassessoril.gov
File an appeal online (Assessor): cookcountyassessoril.gov/online-appeals
Cook County Board of Review: cookcountyboardofreview.com
Board of Review appeal portal: appeals.cookcountyboardofreview.com
Illinois Property Tax Appeal Board (PTAB): ptab.illinois.gov The appeal process isn't glamorous. Nobody's going to throw you a parade for filing a form online. But if your assessed value is wrong — and statistically, there's a decent chance it is — you're leaving money on the table every single year you don't appeal. It's free. It takes 20 minutes. Just do it. Same energy applies to fighting a local parking ticket — the system counts on you not bothering.
