DuPage County Property Tax, Assumed Business Name and Permit Guide

DuPage County is the most densely developed county west of Chicago, and nearly every household and business in it deals with the same short list of county offices in Wheaton. This guide explains DuPage County property tax from assessment to tax sale, how to appeal, how to register an assumed business name, and which permits come from the county rather than your village or city. It is aimed at homeowners, landlords and small business owners in towns such as Naperville, Wheaton and Warrenville.

Which DuPage County offices do what?

The townships are Wayne, Bloomingdale, Addison, Winfield, Milton, York, Naperville, Lisle and Downers Grove. Your parcel number begins with a two-digit township code.

How does DuPage County property tax work?

The county explains the cycle in two halves. In the assessment half, township assessors enter a value for each parcel between January 1 and November 15 of the assessment year. In general reassessment years (the county cites 2019 and 2023) they revalue everything; in other years they adjust properties with physical changes. The Supervisor of Assessments then runs a three-year sales study, applies an equalization factor if a township is out of line, mails change notices, schedules appeals and lets the Board of Review certify the roll. The state may add a final equalization factor.

In the levy half, the County Clerk applies exemptions, divides each taxing body's request by its taxable value to produce a rate, and passes the data to the Treasurer. Bills usually go out in the last week of April, and the Treasurer must mail them by May 1.

A postal postmark, not a meter mark, decides timeliness. If your lender escrows taxes, check before paying: the Treasurer reported handling nearly $4 million in duplicate payments in a recent year.

How do you appeal an assessment in DuPage County?

1. Speak to your township assessor and review the property record.
2. Collect at least three comparable properties. For a market-value appeal use recent sales; for a uniformity appeal use similar properties in your neighborhood.
3. File with the Board of Review through the SmartFile e-filing system before the township deadline, which is 30 days after the township roll is published.
4. Wait for the written decision, which the Board typically mails the following March.
5. If you disagree, you may go to the Property Tax Appeal Board or to court.

An appeal challenges the value, not the amount of the bill. Sample 2026 filing deadlines from the county's assessment status page:

The Supervisor's office reports granting more than 75,000 senior homestead exemptions and processing nearly 11,000 senior freeze exemptions for the 2025 tax year payable in 2026, which shows how common these reductions are. Details of the general homestead, senior, disability and veterans exemptions are on the county's exemptions pages.

How do you register an assumed business name in DuPage County?

Sole proprietorships and general partnerships located in DuPage County must register when the name is anything other than the owners' own names. LLCs, LLPs and corporations register with the Illinois Secretary of State instead; see our assumed name and county clerk guide.

1. Complete the Certificate of Ownership of a Business application and present photo ID with your current address. Each owner signs; mailed filings need notarized signatures.
2. File in person at the County Clerk in Wheaton, or mail it with a $10 check or money order.
3. Publish the notice in a local newspaper for three consecutive weeks.
4. File the newspaper's Certificate of Publication within 50 days of its file stamp, or the registration is void.
5. Receive the Assumed Business Name certificate; a duplicate costs $5.

A name change means a new application and new publication. Adding an owner requires publication when the change is 25% or more of ownership. The clerk's page does not describe renewal, so confirm with the office.

What permits does DuPage County issue?

• Building and zoning: the county department handles permits for unincorporated areas, plus zoning, regional planning, contractor registration, code enforcement and liquor and gaming matters. Inside Naperville, Wheaton and other municipalities, use the municipal building department.
• Food: the Health Department permits and regulates more than 4,000 food service facilities and offers self-guided training for opening or remodeling one.
• Wells and septic: also a Health Department program, relevant outside municipal water.
• Courts: business disputes are filed with the Clerk of the Circuit Court of the 18th Judicial Circuit.

See the Illinois local licenses, permits and zoning guide for the sequence of approvals.

What sales tax rate applies in DuPage County?

Illinois's Department of Revenue announced that the regional transit tax rises by 0.25 percentage point in Cook, DuPage, Kane, Lake, McHenry and Will counties on August 1, 2026. The county-level general merchandise rate in the state's rate file is now 7.25%, and municipalities add their own, so Naperville is 8.00%, Wheaton and Warrenville 8.50%. Use the state's Tax Rate Finder for an exact address and read the Illinois sales and use tax guide.

Where can a DuPage business get help?

The Illinois SBDC network lists a center at College of DuPage in Glen Ellyn, and a second at Waubonsee Community College serves the Aurora area. Local chambers of commerce are a quick way to meet lenders and landlords. Our small business resources guide lists financing options.

Which towns are covered?

• Naperville, which also extends into Will County
• Wheaton, home of the county seat
• Warrenville, mostly in Winfield Township
• Bolingbrook and Aurora, which each have small DuPage sections

Mistakes to avoid

• Assuming the township or county sets your tax rate; school and park districts drive most of it.
• Missing the 30-day window after your township's notice.
• Paying a delinquent bill with a personal check after certified funds are required.
• Filing an assumed name when an LLC filing is what applies.

How we can help

We are a CPA firm in the Aurora and Fox Valley area serving DuPage clients with U.S. returns, Illinois registrations, sales tax, payroll and bookkeeping, and we coordinate with your Canadian CPA or Indian Chartered Accountant when income or property crosses borders. Explore business formation and registrations, sales tax and GST compliance or IRS and state tax representation.

Frequently asked questions

General information only. It is not tax, legal, accounting or immigration advice for your situation, and rules change; confirm the current rules with the official source or a licensed professional in the relevant country.