How to Appeal Property Taxes in DuPage County, Illinois (2026 Guide)

As of July 27, 2026, DuPage County has not yet posted the 2026 township publication dates or final complaint deadlines on its Assessment Status page; the latest posted chart is still the 2025-pay-2026 cycle, whose deadlines are all closed. The rule to watch is simple: file with the DuPage County Board of Review, 421 N. County Farm Road, Wheaton, IL 60187, no later than 30 days after legal publication of your township assessment roll; faxed and emailed appeals are not accepted. (dupagecounty.gov)

How assessments work in DuPage County

DuPage does not have one county assessor setting every value. The county has nine township assessors who make the initial assessed valuation; the Supervisor of Assessments provides statistical analysis, equalization, publishes assessment changes, mails change notices, and acts as clerk for the Board of Review. (dupagecounty.gov)

Illinois residential assessments are aimed at roughly one-third of fair market value before exemptions. For a 2026 appeal, the useful question is usually: “Does my 2026 assessed value × 3 overstate what my home was worth on January 1, 2026?” DuPage’s own appeal guidance says assessed values are based on the three prior years of actual sales transactions; for 2026, that means sales from 2023, 2024, and 2025. (dupagecounty.gov)

The 2026 cycle is a non-general assessment year after the 2023 general assessment cycle. DuPage’s assessment-cycle page identifies general assessment years such as 2019 and 2023; in non-general years, township assessors enter values for properties with physical changes or properties they choose to revalue individually. (dupagecounty.gov)

The county’s 2026 exact deadlines are township-specific, not countywide. The Assessment Status page explains that the “Final Date for Filing Assessment Complaints” is the Board of Review deadline for each township, but as of this writing it still displays the 2025 chart: Downers Grove closed September 15, 2025; Bloomingdale September 29; Lisle October 14; Wayne October 20; Naperville October 24; Winfield October 27; York November 17; Addison and Milton November 24. Do not use those as 2026 dates. (dupagecounty.gov)

Whether you should appeal

Appeal if you can prove one of two DuPage-specific points: market value or uniformity. Market value means your assessment implies too high a sale price. Uniformity means similar homes in your township/neighborhood are assessed lower even if the market value is roughly right. DuPage says the best evidence is a recent appraisal, a recent sale of the subject property, or recent sales of similar properties. (dupagecounty.gov)

Start with your township assessor before filing. The Board’s own rules strongly recommend discussing the assessment with the township assessor first because errors in the property record card may be corrected without a Board appeal. But this conversation does not extend your deadline. (dupagecounty.gov)

Pull your property card and check: parcel prefix/township, class, land size, living area, basement, finished basement, garage, air conditioning, fireplace, condition, neighborhood code, sale history, and exemptions. DuPage’s Residential Comparison Grid asks for those exact items because the Board uses them to decide whether your comparables are truly similar. (dupagecounty.gov)

Also check exemptions before assuming the assessment is the whole problem. DuPage’s forms page says the General Homestead (Residential) Exemption is for an owner’s principal residence and is administered by township assessors, generally automatically. The Homestead Improvement Exemption can reduce assessed value up to $25,000 for four years when an existing owner-occupied home’s assessment rises because of a new physical improvement. The county also administers senior, senior freeze, disabled persons, and veterans exemptions. (dupagecounty.gov)

Step-by-step how to file

1. Find your township and deadline. Your parcel number’s first two digits identify the township. Watch the county Assessment Status page after publication; the 2026 filing deadline will be listed there by township. (dupagecounty.gov)

2. Use the right form. For a homeowner, use Residential Assessed Value Appeal Form (Blank) or Residential Assessed Value Appeal Form (Fill-In and Print). If appealing uniformity or excessive market value, complete the Residential Comparison Grid included with the residential form. The county also posts commercial/industrial forms, undervaluation forms, intervention forms, and attorney authorization forms. (dupagecounty.gov)

3. Prepare evidence. DuPage asks for three or more comparable properties, preferably in the same neighborhood. For market value, use recent sales; for uniformity, use similar properties with similar amenities and lower assessments. The residential grid allows three to five comparables. (dupagecounty.gov)

4. Make copies. The county appeal page says appeal forms and evidence must be submitted in duplicate. The 2025 residential form says to submit two copies of the appeal and two copies of evidence. (dupagecounty.gov)

5. File on paper with the Board of Review. Address all communications to: DuPage County Board of Review, 421 N. County Farm Road, Wheaton, IL 60187. The Board’s meetings and hearings are at the Jack T. Knuepfer Administration Building at that address. Mailings with a USPS postmark are deemed filed on the postmark date; delivery-service filings count as filed on the shipping-label date. (dupagecounty.gov)

6. Do not email or fax. The Board rules say: “Faxed or e-mailed appeals will not be accepted.” The official rules and forms do not list an online homeowner appeal portal or a filing fee; if the county adds one for 2026, the Board of Review page is the place to verify before relying on it. (dupagecounty.gov)

What happens after

The appeal authority is the DuPage County Board of Review, a quasi-judicial agency and the final local authority for uniform and equitable assessments. It has three regular members, may use expanded members, and can lower or raise assessments after notice and hearing where required. (dupagecounty.gov)

On the residential form, you choose either “I DO wish to be heard” or “I DO NOT wish to be heard.” If you choose no hearing, the Board decides on the submitted evidence and you still preserve the right to appeal to the Illinois Property Tax Appeal Board. The form states that all appeals are treated equally regardless of that choice. (dupagecounty.gov)

If there is a hearing, the Board controls the procedure, may admit or exclude evidence, may ask for records, and may request a property inspection. Hearings are open to the public, and a single regular or alternate member may conduct the hearing, but no assessment-appeal decision is final without concurrence from a full Board member. (dupagecounty.gov)

Expect a slow result. DuPage says written Board decisions are mailed after all county hearings are complete, typically the following March, and no decisions are released before then. For the 2025-pay-2026 cycle, DuPage posted that decision notices would be mailed March 18, 2026. (dupagecounty.gov)

If you lose, you may appeal to the Illinois Property Tax Appeal Board (PTAB) within 30 days of the Board decision notice, or choose the court route; you cannot treat the Board appeal as a protest of the tax bill itself. (dupagecounty.gov)

Local tips

Use your township’s assessor data for comps, but do not rely only on Zillow-style estimates. DuPage’s grid wants assessor-specific facts: neighborhood, land square footage, structure type, age, baths, living area, basement, central air, fireplaces, garage, decks, sale date, sale price, and assessment per square foot. (dupagecounty.gov)

For savings, use your actual tax code, not a county average. Example: a Lombard/York Township parcel in the county property lookup shows a 2025 payable-2026 total tax rate of 7.4897%. If that homeowner proves the assessment should fall from $150,000 to $141,667—a $25,000 market-value reduction divided by three—the estimated annual tax savings would be about $624: $8,333 × 0.074897. Your result may be higher or lower because DuPage tax rates vary by school district, municipality, park district, library, fire district, and township. (propertylookup.dupagecounty.gov)

Do not wait for the tax bill. The bill comes after the assessment appeal window has closed. The practical trigger is your township’s legal publication and Assessment Status deadline, not the due date on the tax bill. (dupagecounty.gov)