To file a DuPage County property tax appeal, submit a written complaint to the county Board of Review within 30 days after your township’s assessment roll is published, and back it up with evidence that your property is either overvalued or assessed at a higher percentage of value than similar homes nearby. Illinois law requires every property to be assessed at 33⅓% of fair cash value, and the Board has authority to correct an assessment that misses that mark.1Illinois General Assembly. Illinois Code 35 ILCS 200/9-145 – Assessment Level Filing costs nothing. The work is in the evidence.
Try the Township Assessor First
Before you file formally, ask your township assessor for an informal review. Each DuPage County township runs its own assessor’s office, and most accept review requests shortly after assessment notices go out, with deadlines that fall before the Board of Review window even opens.2DuPage Township. DuPage Township Assessor
This step matters because township assessors can fix errors in your property record directly: incorrect square footage, a finished basement that isn’t finished, a bathroom that was never built. If the assessor agrees your value is off, the correction happens before you ever file a complaint. If the informal review doesn’t produce a satisfactory answer, your right to file with the Board of Review is still intact.
The Two Grounds That Actually Win
The Illinois Property Tax Code lets the Board hear complaints that a property is overassessed or underassessed and correct the assessment as it sees fit.3FindLaw. Illinois Code 35 ILCS 200/16-55 – Complaints Homeowners typically appeal on one of two grounds.
Overvaluation
An overvaluation argument says the assessor’s estimate of your home’s fair market value is simply too high. Because Illinois assessments are set at 33⅓% of market value, an inflated market value estimate inflates your assessed value and your tax bill with it.1Illinois General Assembly. Illinois Code 35 ILCS 200/9-145 – Assessment Level If the county values your home at $450,000 but comparable sales put it closer to $375,000, your assessment is built on a number no buyer would pay. A recent purchase price, a certified appraisal, or a pattern of lower sale prices in your neighborhood all support this argument.
Lack of Uniformity
A uniformity argument is different. You’re not disputing market value. You’re saying your property is assessed at a higher percentage of value than similar homes in the same district, which the statute prohibits.3FindLaw. Illinois Code 35 ILCS 200/16-55 – Complaints If your neighbors’ homes are assessed at 30% of market value while yours sits at 34%, you have a uniformity problem even when your own number looks defensible in isolation. The Board evaluates this by comparing assessment-to-sale ratios across comparable properties.
Evidence the Board Will Actually Read
The Board won’t lower your assessment because you feel your taxes are too high. It responds to data.
Start with your property’s record through the DuPage County Property Lookup Portal or your township assessor’s website.4DuPage County. Supervisor of Assessments – Property Lookup Portal The property record card lists every physical characteristic the assessor used to calculate value: lot size, building square footage, number of rooms, construction type, basement status. Read every line. Errors here are the lowest-hanging fruit in a tax appeal. Correcting a single wrong data point can shift the result.
Then find at least three comparable properties. The county’s own instructions call for three or more comps that share similar characteristics with your home.5DuPage County, IL. Appeal Process Look for similar age, style, lot size, and square footage. For an overvaluation argument, pick comps that recently sold for less than the assessor’s estimate of your home’s market value. For a uniformity argument, pick comps whose assessed values represent a lower percentage of their sale prices than yours does.
A Recent Sale or a Certified Appraisal
If you bought your home recently, the closing statement is strong evidence. It shows what a willing buyer actually paid in an open-market transaction, which is the textbook definition of fair market value. Bring it even when you’re relying on comps too.
A certified appraisal from a licensed Illinois appraiser carries weight because it follows the Uniform Standards of Professional Appraisal Practice. A broker price opinion is not the same thing and won’t carry the same credibility with the Board. Residential appraisals typically run $500 to $1,200, so they make sense when the potential tax reduction justifies the spend.
Filing the Complaint
Appeal forms are on the DuPage County Supervisor of Assessments website, with separate versions for residential and commercial properties.6DuPage County. Supervisor of Assessments – Forms and Documents You’ll need your Permanent Index Number (on your assessment notice or tax bill), the current assessed value, and the assessed value you believe is correct. You’ll also say whether you want to attend a hearing in person.
The core of the form is a comparison grid where you enter data from your comps alongside your own property: lot size, building square footage, year built, sale prices. This grid is what Board members actually review. Three strong comps that genuinely resemble your home do more work than six weak ones. Submit the forms and all supporting evidence in duplicate.
The 30-Day Deadline
The filing window closes 30 days after the township assessment roll is published.5DuPage County, IL. Appeal Process Each township publishes on its own schedule, so deadlines vary. The county posts the publication dates and corresponding deadlines on its website. Board of Review appeals for the 2025 assessment year (the taxes you pay in 2026) typically open in August, with deadlines falling in mid-to-late September.7DuPage Township. Assessment Review Miss the deadline and you lose the right to appeal for that tax year. The Board does not grant extensions.
What Happens at the Hearing
After filing closes, the Board schedules hearings and notifies each appellant of a date and time. You can attend in person or let your written submission stand on its own. In-person hearings are short and focused on the facts in your file. Board members may ask about your comps, your property record, or the basis for your requested value. It’s not a courtroom. Stay factual and stick to your data.
The Board mails written decisions after all hearings in the county are complete. For the 2025 assessment year, the Board indicated it would mail decisions on March 18, 2026.8DuPage County, IL. Board of Review If the Board agrees you were overassessed, the decision letter shows the adjusted value, and that new number drives your next tax bill.
If the Board Denies You
A denial is not the end. Illinois gives you two further options: the state Property Tax Appeal Board (PTAB) or your county’s circuit court.9Illinois Department of Revenue. Assessment Appeals – Property Tax You have to choose one. You can’t pursue both.
A PTAB appeal must be filed within 30 days of the Board of Review’s written decision notice.10Illinois General Assembly. Illinois Code 35 ILCS 200/16-160 – Property Tax Appeal Board Proceedings PTAB has its own forms, available through the Illinois Department of Revenue or the DuPage County Supervisor of Assessments office.8DuPage County, IL. Board of Review The PTAB process is more formal than the county Board of Review but still doesn’t require an attorney. A circuit court challenge is full litigation and almost always does. Most homeowners start with PTAB.
Keep Paying Your Taxes While You Appeal
Filing an appeal does not pause your tax obligation. Illinois requires you to pay your property taxes on time while any appeal is pending at any level.9Illinois Department of Revenue. Assessment Appeals – Property Tax If you win and your assessed value drops, you’ll receive a refund or credit for the overpayment. If you skip payments while waiting on a decision, you can face penalties, interest, and eventually a tax sale on your property.
One Note on a Successful Refund
If you itemized on your federal return and deducted the original property tax payment, a refund from a successful appeal may need to be reported as income in the year you receive it, under the IRS tax benefit rule.11Internal Revenue Service. Publication 525 – Taxable and Nontaxable Income If the original deduction didn’t actually reduce your federal tax (because you took the standard deduction, for example), the refund usually isn’t taxable. IRS Publication 525 includes a worksheet for figuring the exact amount.