If you believe your Cook County property is over-assessed — and many are — you have a legal right to challenge that assessment. The appeal process is free, is available to every property owner, and at the Assessor and Board of Review levels does not require an attorney. Yet most homeowners never file. This guide walks you through the entire appeal system from start to finish so you know exactly what to do, what to expect, and where to go at every stage.
The appeal hierarchy: Cook County property tax appeals move through three levels — (1) the Cook County Assessor's Office, (2) the Cook County Board of Review, and (3) the Illinois Property Tax Appeal Board (PTAB) or Circuit Court. You must generally exhaust each level before proceeding to the next.
Overview: The Three Levels of Appeal
Level | Body | Deadline | Cost | Attorney Required? |
|---|---|---|---|---|
Level 1 | Cook County Assessor | 30 days from Notice of Proposed Assessment | Free | No |
Level 2 | Cook County Board of Review | Township-specific window (check borc.cookcountyil.gov) | Free | No |
Level 3 | PTAB or Circuit Court | 30 days from Board of Review decision | Filing fees apply; attorney typical | Strongly recommended |
Before You File: Gather Your Evidence
A successful appeal rests on evidence. Assembling your evidence before filing is the single most important step. Here is what to collect:
1. Your Property Index Number (PIN)
Every Cook County property has a 14-digit PIN. It appears on your Notice of Proposed Assessment, your tax bill, and on the Cook County Treasurer website at cookcountytreasurer.com. You need your PIN to look up your property record card and to file an appeal.
2. Your Property Record Card
The property record card is the Assessor's file on your property. Go to cookcountyassessor.com, enter your PIN, and review every detail:
☐ Square footage — is it correct?
☐ Number of bedrooms and bathrooms
☐ Lot size (for single-family homes)
☐ Construction type, building quality classification
☐ Presence of basement, garage, fireplace
☐ Renovation or improvement dates
Errors in the property record card are one of the easiest and most clearcut bases for a successful appeal. If the Assessor thinks you have 2,400 square feet when you actually have 1,800, that discrepancy alone can justify a significant reduction.
3. Comparable Sales (Your Strongest Evidence)
Pull three to five recent, arm's-length sales of properties similar to yours. "Arm's-length" means a standard market transaction — not a sale between relatives, a foreclosure sale, or a distressed sale. The best comparable sales:
☐ Closed within the past 12 months
☐ Located within approximately half a mile of your property
☐ Same property type (condo vs. condo; SFH vs. SFH)
☐ Similar size (within 20–25% of your square footage)
☐ Similar age, construction type, and amenities
If those sales support a market value lower than what the Assessor's implied value suggests (your AV divided by 0.10), you have a compelling case. A real estate professional can pull this data for you from the MLS — reach out to the Camille Canales Group for help.
4. Your Purchase Contract (If You Bought Recently)
If you purchased your property recently and paid less than the Assessor's implied market value, your purchase contract is powerful evidence. The purchase price of an arm's-length sale is generally considered the best indicator of market value. Submit a copy of your closing statement (HUD-1 or ALTA settlement statement) along with your appeal.
5. Photos of Property Condition
If your property has deferred maintenance, significant repair needs, or physical conditions that would reduce its market appeal — a dated kitchen, a cracked foundation, unfinished areas — photographs can support your argument that the Assessor's value is too high. This evidence is supplementary and most useful when combined with comparable sales.
6. A Recent Appraisal (Optional but Powerful)
A full appraisal from a licensed appraiser is the strongest possible evidence of market value, but it is not required and typically costs $400–$600 for a residential property. For properties where the potential tax savings are substantial — say, a large single-family home or a multi-unit building — an appraisal is often worth the investment. For a smaller condo where the savings might be $500–$1,000 per year, comparable sales alone usually suffice.
Level 1: Appealing to the Cook County Assessor
The first level of appeal is filed directly with the Cook County Assessor's Office. This is your first and often best opportunity to correct an over-assessment before it is locked in.
When to File
You must file within 30 days of the date on your Notice of Proposed Assessment. The notice date and deadline are printed on the letter. This deadline is firm — the Assessor will not accept late filings.
Where to File
File online at assessor.cookcountyil.gov. The online portal is straightforward and walks you through each step. You will enter your PIN, upload your evidence documents, and submit your requested value. You can also file in person at the Assessor's office at 118 N. Clark Street, Chicago.
What to Submit
The online portal will ask for the basis of your appeal (comparable sales, property record error, or both) and will prompt you to upload supporting documents. A well-organized submission includes:
☐ A completed appeal form (generated by the portal)
☐ A comparable sales grid (the portal has a template)
☐ MLS printouts or public records confirming each comparable sale
☐ Your purchase contract (if applicable)
☐ Photos or documentation of any property record errors
What to Expect
The Assessor reviews your submission and may reduce, maintain, or (very rarely) increase your assessment. You will receive a written decision — typically within several weeks to a few months. There is no hearing at this level; it is a document review. If the Assessor reduces your assessment, that lower value carries forward. If you are not satisfied, you may appeal to the Board of Review regardless of the outcome.
Level 2: Appealing to the Cook County Board of Review
The Board of Review (BOR) is a three-member independent body — separate from the Assessor — that reviews assessment appeals. It has authority to reduce, increase, or sustain any assessment. The BOR is the second bite at the apple, and many property owners find success here even after being denied at the Assessor level.
When to File
Unlike the Assessor appeal (which is triggered by your notice), the BOR operates on a township-by-township calendar that it publishes each year. Each of Cook County's 38 townships has a specific appeal window — typically a few weeks during the fall. You must file during your township's open window, which is independent of whether or when you received an Assessor notice. Check the current BOR calendar at borc.cookcountyil.gov.
Critical note: You can file a BOR appeal in any year — not just reassessment years. If you missed the Assessor appeal window or want a second review, the BOR is your path every year.
Where to File
File online at borc.cookcountyil.gov. The BOR has a separate online filing system from the Assessor. You will need your PIN and supporting evidence. Filing in person is also available at 118 N. Clark Street, Suite 601, Chicago.
The BOR Process
The BOR process is more formal than the Assessor appeal. You submit your evidence in writing, and the BOR may schedule an informal hearing (a brief meeting with a BOR analyst) or simply review your submission on the papers. Many residential appeals are resolved on the papers without a hearing. For commercial properties and large residential cases, hearings are more common.
The BOR will issue a written decision. Resolution typically takes several months. The BOR decision is the final administrative level; if you are not satisfied, your only remaining options are PTAB or Circuit Court.
Level 3: Illinois Property Tax Appeal Board (PTAB) or Circuit Court
If you exhaust both the Assessor and Board of Review levels without a satisfactory result, you have two options for further appeal: the Illinois Property Tax Appeal Board (PTAB) or the Cook County Circuit Court. These are the most formal and complex levels of the process.
Illinois Property Tax Appeal Board (PTAB)
PTAB is a state administrative body that hears property tax appeals from all 102 Illinois counties. It operates much like a quasi-judicial proceeding — formal rules of evidence apply, you may present testimony and expert witnesses, and the BOR or Assessor's office will typically defend the assessment. Most residential property owners who take cases to PTAB work with a property tax attorney. The filing deadline is 30 days after the Board of Review issues its decision. Cases can take one to several years to resolve at PTAB.
Circuit Court
An alternative to PTAB is filing a tax objection complaint in the Cook County Circuit Court. This route is generally more expensive and complex, and is most often used by commercial property owners or in cases involving large tax amounts. An attorney is essential.
For most homeowners: The practical sweet spot of the appeal process is Levels 1 and 2. These are free, accessible, and resolve the vast majority of residential property tax appeals. PTAB and Circuit Court are appropriate for high-value properties or persistent, significant over-assessments where the potential savings justify the legal costs.
DIY vs. Hiring a Property Tax Attorney
One of the most common questions we hear is whether to handle the appeal yourself or hire a tax attorney or consultant. Here is an honest breakdown:
Scenario | Recommended Approach | Why |
|---|---|---|
Residential condo or SFH, clear evidence (recent purchase or obvious comparable sales) | DIY — file yourself | Process is designed for self-representation; attorney fee may exceed savings |
High-value SFH, multi-unit, or commercial property | Consider a tax attorney or consultant | Larger potential savings justify contingency fee; more complex evidence needed |
Assessor and BOR both denied; considering PTAB | Attorney strongly recommended | Formal proceedings; rules of evidence; BOR will be represented |
Complex ownership structure (LLC, trust, estate) | Consult an attorney | Ownership complexity can affect standing and strategy |
On contingency fees: Many property tax attorneys and consultants work on contingency — they take 33% to 50% of your first-year savings if they win, and nothing if they do not. For a residential property where the potential savings are $800/year, that means you keep $400–$534 and the attorney takes the rest. For a property where savings might be $5,000/year, contingency makes much more sense.
Common Mistakes That Sink Appeals
Missing the Filing Deadline
The number one reason appeals fail is never getting filed. The 30-day Assessor window is firm. Put the deadline on your calendar the moment the notice arrives.
Submitting Weak or Irrelevant Comparables
Using sales that are too old, too far away, or too different from your property undermines your case. The Assessor and BOR will discount comparables that do not reflect your property type, location, and timeframe. Three strong, highly similar comparables are worth more than ten marginal ones.
Confusing the Tax Bill with the Assessment
You appeal the assessed value, not the tax bill. The tax bill is a result of the assessment, the equalization factor, your exemptions, and the tax rate — only the assessment is subject to appeal. Understanding this distinction helps you frame your argument correctly.
Filing Without Evidence
Simply asserting "this is too high" without documentation almost never succeeds. The Assessor and BOR make decisions based on evidence. An appeal without comparable sales data, an appraisal, or documented property record errors gives the reviewing body nothing to work with.
Using Distressed Sales as Comparables
Foreclosure sales, short sales, estate sales, and transactions between related parties are not arm's-length market sales and will be rejected as comparables. Only use standard market transactions.
Waiting for Reassessment to Appeal
You do not need to wait for a reassessment year to file a Board of Review appeal. If your property was over-assessed three years ago and has been carrying that inflated value, you can appeal during any township's open BOR window. Do not leave savings on the table waiting for the next reassessment cycle.
What Happens After a Successful Appeal
If your appeal results in a reduced assessment, the new lower value is reflected in your tax bill going forward. The reduction applies from the tax year in which you appealed. You will not typically receive a refund for taxes already paid on an excessive assessment from prior years (though PTAB decisions can sometimes result in refunds for the applicable tax year). The lower assessed value generally carries forward until the next reassessment, unless you appeal again or the property is otherwise re-evaluated.
A Word on Exemptions
While you are looking at your assessment, verify that all of your exemptions are in place. The Homeowner Exemption saves approximately $700–$900 per year depending on your tax rate and is available to any owner-occupant. Senior exemptions, disability exemptions, and veterans exemptions provide additional relief. Check your exemption status at cookcountyassessor.com. Missing exemptions are sometimes as valuable as winning an appeal — and easier to fix.
Free Cost to File Assessor and Board of Review appeals cost nothing to file. No barriers to entry. | 3 Levels of Appeal Assessor → Board of Review → PTAB or Circuit Court. Each level is a fresh review. | 30 Days to Appeal Your window from the Notice of Proposed Assessment to file with the Assessor. Non-negotiable. |
Continue Reading
Part of the Camille Canales Group property tax education series:
→ Chicago Property Taxes Explained: Key Dates, Tools, and Expert Help
→ Cook County Reassessment Years: What Chicago Homeowners Need to Know
→ The Property Tax Appeal Checklist for Chicago Homeowners
→ What a Successful Property Tax Appeal Actually Looks Like: A Logan Square Case Study
→ Property Tax Appeal FAQ: Every Question Chicago Homeowners Ask Us
Ready to Appeal Your Assessment?
The Camille Canales Group can pull comparable sales data and help you evaluate whether an appeal makes sense for your property. We do this regularly for our clients — it is part of what we do as a full-service Chicago real estate team.
Camille Canales Group | Compass | ccg-chicago.com | 773-377-9200. This article is for informational purposes only and does not constitute legal or tax advice. Deadlines and procedures are subject to change; always verify current information at assessor.cookcountyil.gov and borc.cookcountyil.gov. Consult a licensed attorney for advice specific to your situation.
