To file a property tax appeal in Cook County, submit a free complaint to the Cook County Assessor’s Office within roughly 30 days of your reassessment notice, supported by evidence that your home is overvalued or assessed more heavily than comparable properties nearby.1Cook County Assessor’s Office. Residential Appeals If the Assessor’s decision disappoints you, you can escalate to the Cook County Board of Review, then to the state Property Tax Appeal Board or the Circuit Court of Cook County. The process is designed for homeowners to handle themselves, but it rewards tight deadlines and good evidence.
Deadlines You Have to Hit
Missing the filing window ends the appeal before anyone looks at your evidence. The Assessor opens and closes appeal periods township by township on a rolling calendar, and the last day to file is printed on your reassessment notice. You generally have about 30 days from the date of that notice.1Cook County Assessor’s Office. Residential Appeals If your township isn’t being reassessed this year, you can still file during the annual window your township is open, but you won’t receive a new notice unless something about the property changed.2Cook County Assessor’s Office. Assessment and Appeal Calendar
The Board of Review opens its own filing period after the Assessor finishes processing appeals for each township, and those dates are posted separately.3Cook County Board of Review. Dates and Deadlines If you want to go beyond the Board of Review to the Property Tax Appeal Board, you have 30 days from the Board of Review’s written decision, or 30 days from the date the Board transmits its final action on your township to the county assessor, whichever is later.4Illinois General Assembly. Section 1910.30 – Filing Petitions for Appeal None of these windows get extended. Miss one and you wait until next year.
What You Can Argue
Illinois law lets property owners file a written complaint when their property is overassessed, and the reviewing body must correct the assessment “as appears to be just.”5Illinois General Assembly. Illinois Code 35 ILCS 200 – Property Tax Code Residential appeals in Cook County almost always rest on one of three grounds, and picking the right one shapes the evidence you’ll gather.
Lack of Uniformity
This is the most common residential argument. You’re saying your property is assessed at a higher rate per square foot than comparable homes in the same neighborhood and classification code. You don’t have to prove your home’s market value is wrong, only that you’re taxed more heavily than similar properties nearby. The Board of Review recommends comparing your home to properties of similar age, construction style, and size within the same neighborhood.6Cook County Board of Review. How to Present a Case – Section: Uniformity
Overvaluation
If the Assessor’s estimated fair market value exceeds what your property would actually sell for, you have an overvaluation claim. A recent purchase price is the strongest evidence here. If you bought within the past year or two and paid less than the assessed market value, the gap is hard to dismiss. An independent appraisal by a licensed appraiser serves the same purpose if you haven’t sold recently. The Assessor’s Office estimates values from sales patterns of comparable homes, so any evidence that the model overshot your property is relevant.7Cook County Assessor’s Office. How Residential Property Is Valued
Factual Errors
Sometimes the records are simply wrong. The property card might list the wrong square footage, an extra bathroom that doesn’t exist, a finished basement that’s actually unfinished, or a building type that doesn’t match reality. These errors inflate your assessment by making the home look bigger or better than it is. You can correct property characteristics through the Assessor’s online portal even outside the formal appeal window.8Cook County Assessor’s Office. File an Appeal Online
Evidence That Actually Works
Start by locating your 14-digit Property Index Number (PIN). Every filing requires it, and you’ll find it on your tax bill, closing documents, or any notice from the Assessor’s Office.9Cook County Assessor’s Office. Where Do I Find My PIN Getting the PIN wrong is one of the fastest ways to have an appeal rejected without review.
For a uniformity argument, pull comparable properties similar to yours in location, class code, age, and square footage. The Assessor recommends Cook Viewer’s Interactive Map, which automatically filters for comparables based on your property’s characteristics.10Cook County Assessor’s Office. What Are Comparable Properties Choose at least three to five properties whose assessed value per square foot is lower than yours. The closer those comparables sit to your home in age, size, and neighborhood, the harder they are for a reviewer to brush aside.
For an overvaluation argument, a recent closing statement showing what you paid is the most persuasive single document. A professional appraisal from a licensed appraiser also carries weight, though appraisals typically cost $400 to $1,500 depending on complexity. Photographs documenting structural damage, deferred maintenance, or environmental problems like a nearby factory, flooding issues, or a busy highway can support either argument by showing conditions that depress value below what the model assumes.
Filing with the Assessor
Filing with the Assessor’s Office is free and can be done online in roughly 20 minutes.11Cook County Assessor’s Office. Overview of How Appeals Work The portal lets you upload supporting documents, enter the current assessed value and the value you believe is correct, and submit everything electronically. You’ll receive a confirmation code for tracking. Separate forms exist for residential, condo/co-op, commercial, and vacant land appeals.8Cook County Assessor’s Office. File an Appeal Online
If you prefer paper, mail the completed application and all supporting evidence to the Assessor’s Office. Use certified mail with a return receipt. That postmark is your proof you met the deadline if timing is ever disputed. Whether you file online or by mail, fill in every required field. Incomplete applications get sent back, and by the time you fix them the window may have closed.
Several weeks or months after the filing period closes, the Assessor’s Office issues a Notice of Proposed Assessed Value telling you whether your assessment was reduced, left unchanged, or (rarely) increased. If the result disappoints, you’ve lost nothing. The Board of Review is next.
If the Assessor Says No: The Board of Review
The Cook County Board of Review is an independent body with authority to revise, correct, or modify any assessment for properties in Cook County.12Illinois General Assembly. Illinois Code 35 ILCS 200 – Property Tax Code – Section 16-95 You don’t need to have filed with the Assessor first; the Board accepts appeals directly. Most people still start with the Assessor because it’s simpler. Filing with the Board is also free and handled through its online portal.
You choose between a file-only appeal and a live hearing. File-only means the hearing officer reviews your written evidence and decides without meeting you. A live hearing lets you make a brief oral presentation and answer questions. Most residential cases resolve file-only, but if the situation involves unusual circumstances, say environmental contamination or a property that doesn’t compare well to its neighbors, a hearing lets you explain context documents can’t carry.
You can submit additional or updated evidence at this stage. If you’ve gathered stronger comparables or obtained an appraisal since filing with the Assessor, include them. The Board typically issues its final decision several months after the hearing phase for each township.
Going Further: PTAB or Circuit Court
If the Board of Review’s decision still falls short, you have two options, and you must choose one. You can’t pursue both for the same tax year.
Property Tax Appeal Board
The Property Tax Appeal Board (PTAB) is a state-level quasi-judicial body that hears appeals from Board of Review decisions across Illinois.13Property Tax Appeal Board. Property Tax Appeal Board You file a petition within 30 days of the Board of Review’s decision, laying out the facts of your objection and the relief you want.14Illinois General Assembly. Illinois Code 35 ILCS 200 – Property Tax Code – Section 16-160 PTAB reviews the assessment based on equity and the weight of the evidence. It does not review tax rates or the total tax bill, only whether the assessed value is correct.
Circuit Court Tax Objection
You can instead file a tax objection complaint in the Circuit Court of Cook County. This route requires you to pay your taxes first and then challenge them. In counties with 3,000,000 or more inhabitants, the complaint must be filed within 165 days after the first penalty date of the final tax installment. The court hears the case without a jury, and the assessment is presumed correct; you carry the burden of proving it wrong by clear and convincing evidence.15Illinois General Assembly. Illinois Code 35 ILCS 200 – Property Tax Code – Section 23-15 That’s a higher standard than the Assessor or Board of Review process, and most homeowners only take this route for large commercial or multi-family disputes where the stakes justify the legal costs.
Check Your Exemptions First
Before investing time in an appeal, confirm you’re receiving every exemption you qualify for. Exemptions reduce your equalized assessed value directly, and missing one costs you every year.
- The Homeowner Exemption is available to anyone who owns and occupies their home as a primary residence, and reduces EAV by $10,000.16Cook County Treasurer’s Office. Homeowner Exemption
- The Senior Citizen Exemption is available to homeowners 65 and older who occupy the property as their primary residence, and provides an additional EAV reduction beyond the standard homeowner exemption.
- The Senior Freeze Exemption, for homeowners 65 or older with household income of $65,000 or less, freezes the property’s EAV at the level it was the year you first qualified. Your bill can still rise if tax rates increase, but the assessed value won’t climb. You must reapply every year.17Cook County Treasurer’s Office. Senior Freeze
Exemptions and appeals aren’t mutually exclusive. Do both. Reduce the assessed value through an appeal, then apply exemptions to the lower EAV.
After You Win
If your mortgage includes an escrow account for property taxes, a successful appeal doesn’t automatically lower your monthly payment. Your lender performs an annual escrow analysis and adjusts contributions based on the most recent tax bill. Once the reduced bill is issued, the lender should recalculate your monthly escrow portion downward during the next analysis cycle, and some lenders refund any surplus that has built up. If your payment doesn’t change after a successful appeal, contact your loan servicer and ask when the next escrow analysis is scheduled.
A successful appeal can also create a small federal tax wrinkle if you itemize deductions. Under the tax benefit rule, when you deduct property taxes on Schedule A in one year and later receive a refund or credit for overpayment, the recovered amount may count as taxable income in the year you receive it.18Internal Revenue Service. Revenue Ruling 19-11 – Recovery of Tax Benefit Items The taxable amount is limited to the actual tax benefit you received, essentially the lesser of the refund or the amount by which your itemized deductions exceeded the standard deduction in the year you claimed them. If you took the standard deduction in the year you overpaid, the refund isn’t taxable at all. Illinois may issue a Form 1099-G reporting the amount.19Illinois Department of Revenue. 1099-G For most homeowners the amount is modest, but it’s worth knowing so it doesn’t surprise you at tax time.