An Illinois property tax appeal starts with a free filing to your county board of review, where you argue that your assessment is too high, out of line with similar properties, or based on wrong facts about your home. If the board denies you or doesn’t cut enough, you have 30 days to escalate to the state Property Tax Appeal Board (PTAB), or you can take a different path through circuit court. The deadlines are short, they vary by county, and missing one ends your case for that tax year.
Grounds That Actually Win Appeals
Illinois recognizes three reasons to challenge an assessment, and the strongest cases lean on more than one.
Overvaluation. The assessor set your fair cash value higher than what the property would sell for. A recent purchase price, a certified appraisal, or comparable sales below your assessed value all support this.
Lack of uniformity. Your assessment is disproportionately high compared to similar homes nearby. Even if the assessor’s number is defensible in isolation, you’re entitled to the same treatment your neighbors get. If comparable houses on your block are assessed at a lower value per square foot, that gap is a valid basis for relief.
Factual errors. The assessor’s records show the wrong square footage, an extra bathroom that isn’t there, a finished basement that’s actually unfinished, or the wrong property classification. These are often the easiest wins because they don’t require a judgment call about market value. If the file says 2,400 square feet and your home is 2,100, the math does the work.
One Cook County wrinkle worth flagging: residential property there is assessed at 10% of fair market value, not the 33 1/3% used in most of the state.1Cook County Assessor’s Office. Classifications of Real Property If your Cook County assessment doesn’t reflect that 10% level, that alone can be grounds to appeal.
Deadlines That Decide Your Case Before It Starts
Miss a deadline and you lose the year. There is no grace period.
Counties Outside Cook
Assessors publish annual assessment changes in local newspapers, and that publication starts a 30-day clock to file with the county board of review.2Property Tax Appeal Board. Practice and Procedures The exact dates shift by township and by when the assessor finishes work, so check your county board of review’s website or call the office to confirm.
Cook County
Cook County publishes reassessment notices township by township, opening appeal windows on a rolling schedule throughout the year. Each township has its own “last file date” on the Assessor’s calendar.3Cook County Assessor’s Office. Assessment and Appeal Calendar Cook County also gives you two bites: you can appeal first to the Assessor’s Office, then again to the Cook County Board of Review, each on its own deadline.
PTAB
If the board of review rules against you, you have 30 days from the date of its written notice to petition PTAB. In Cook County, the clock runs from the board of review’s notice or the date the board transmits its final action for your township to the county assessor, whichever is later.4Illinois General Assembly. Illinois Compiled Statutes 35 ILCS 200/16-160 – Property Tax Appeal Board Process File late and PTAB loses jurisdiction. The case is done.
Evidence the Board Will Take Seriously
The board isn’t going to reduce your assessment on your word. Evidence quality decides the outcome.
Start With Your PIN
Every parcel has a Property Index Number printed on your tax bill or assessment notice.5Illinois Department of Revenue. Property Tax Number Information You need it to look up your record and to identify the comparable properties you’ll cite.
Comparable Properties
Pull three to five properties similar in age, size, style, and location. For a uniformity argument, compare assessed value per square foot of living area. If your home is at $120 per square foot and similar homes on your block sit at $95, that disparity tells a clear story. For an overvaluation argument, use recent sale prices of similar properties to show the market doesn’t support the assessor’s figure.
A Certified Appraisal
A USPAP-compliant appraisal is the strongest single piece of evidence, especially if you plan to escalate to PTAB. It includes a full inspection, adjusted comparable sales analysis, and a documented value conclusion. Printouts from online estimators don’t carry the same weight. For a PTAB case, an appraisal is effectively a necessity.
Supporting Documents
Bring anything else that helps: a settlement statement if you bought the property recently, repair estimates for major deficiencies, photographs of condition problems, and surveys or measurements if you’re contesting square footage or lot size. Present it cleanly. A disorganized submission tells the hearing officer you haven’t done the work.
Filing With the County Board of Review
Download the appeal form from your county board of review’s website. Counties often use separate forms for residential, commercial, farm, and industrial properties. The form asks for your PIN, a description of your property, your grounds for appeal, the PINs of your comparable properties, and your supporting documents.
Larger counties usually accept filings through online portals where you upload everything digitally. Smaller counties may require paper submissions by mail or in person. The board schedules a hearing where you walk a hearing officer through your evidence and answer questions. It’s less formal than court. A written decision follows, and any reduction is applied to your assessment.
Escalating to PTAB or Circuit Court
If the board of review denies your appeal or reduces the assessment less than you think it should have, you have two options, and you have to pick one.
PTAB is the state-level administrative route. File within 30 days of the board of review’s written decision.6Property Tax Appeal Board. Property Tax Appeal Board – Frequently Asked Questions PTAB reviews your evidence independently and isn’t bound by the local board’s conclusions. Cases can take a long time, sometimes years, but the process is designed for homeowners to handle without an attorney if the evidence is solid.
The trade-off: filing with PTAB means you cannot also challenge the same year’s assessment through a circuit court tax objection complaint on valuation grounds.4Illinois General Assembly. Illinois Compiled Statutes 35 ILCS 200/16-160 – Property Tax Appeal Board Process Decide before you file.
There’s a useful protection for slow PTAB cases. If PTAB lowers your assessment after the board of review’s filing window for the following year has already closed, you can appeal that next year directly to PTAB within 30 days of the decision.7Illinois General Assembly. Illinois Compiled Statutes 35 ILCS 200/16-185 That keeps you from losing ground while a case drags.
The circuit court route works differently. You must first pay all taxes due within 60 days of the first penalty date on your final installment, and that payment counts as being made under protest automatically. No separate protest letter needed. You then file the complaint within 165 days of the first penalty date in Cook County, or 75 days elsewhere. The court hears the case without a jury, and you carry a clear and convincing evidence burden, which is higher than what PTAB applies. You also need to have exhausted your remedy at the board of review first.8Illinois General Assembly. Illinois Compiled Statutes 35 ILCS 200/23-10 – Tax Objection Filing Deadlines Circuit court is more common for commercial properties and high-value disputes where hiring an attorney makes sense.
Keep Paying While You Appeal
Filing an appeal does not pause your tax obligation. The Illinois Supreme Court has said that paying is not a prerequisite to filing a PTAB appeal, but skipping payment exposes you to penalties and interest. Cook County late payments accrue interest at 1.5% per month.9Cook County Treasurer. Late Property Tax Bill Penalties A successful appeal won’t erase penalties you piled up while waiting.
Pay on time. If you win, the county issues a refund or credit for the overpayment.
Check Your Exemptions Before You Appeal
An exemption you’re entitled to but haven’t claimed can save you as much as a successful appeal, and it’s far easier to get. Verify these first.
The General Homestead Exemption applies to your primary residence and reduces your equalized assessed value by up to $10,000 in Cook County, $8,000 in counties bordering Cook, and $6,000 elsewhere.10Illinois Department of Revenue. Property Tax Relief – Homestead Exemptions
The Senior Citizens Assessment Freeze locks in your equalized assessed value at the level it was when you first qualified, if you’re at least 65 and household income is at or below the threshold. That threshold is $75,000 for the 2026 tax year, $77,000 for 2027, and $79,000 for 2028 and later.10Illinois Department of Revenue. Property Tax Relief – Homestead Exemptions
Additional exemptions exist for disabled persons, disabled veterans, and returning veterans. Your county assessor’s office can confirm what you qualify for. Exemptions and appeals are not either-or. Pursue both.
After a Successful Appeal
A win at the board of review or PTAB lowers your assessed value and reduces what you owe. If you’ve already paid the full tax bill, the county issues a refund or applies a credit to your next bill. Timing depends on where in the cycle the decision arrives and how fast your county processes adjustments.
If your property taxes go through a mortgage escrow account, send your lender a copy of the decision. Lenders run an annual escrow analysis and should reduce your monthly payment to reflect the lower tax figure, and some will refund an escrow surplus directly. Don’t wait for the lender to catch it on their own.
One reduction doesn’t lock in future years. Assessors can and do reassess, so watch your notice each year and be ready to appeal again if the number climbs back up.