Cook County Property Tax, Business Registration and County Taxes

Cook County is the one county on this list where the property tax calendar, the assessment cycle and the county's own business taxes all work differently from the collar counties around it. If you own a condominium in Chicago, a rental building in a suburb, or part of a business that crosses the county line near Elgin, you need to know which rules apply. This guide explains Cook County property tax, the 2026 reassessment, how to register an assumed business name, and which county-level taxes and licenses sit on top of Illinois's.

How is Cook County different from Kane, DuPage and Will?

The rows come from each county's own published pages. See the Kane, DuPage and Will guides for those calendars.

What are the Cook County property tax due dates?

The Treasurer lists the following for recent years:

The pattern shows why Cook owners should watch the Treasurer's page every year: the second installment has landed anywhere from August to December. The Assessor explains that exemptions appear only on the second installment bill, and that a new value from a reassessment affects the second installment the following year. Payment options include online by bank account, credit card, ACH, wire, a community bank or Chase, and by mail or in person, with a payment plan calculator available.

What does the 2026 Cook County reassessment mean for you?

Cook rotates reassessment among the north suburbs, the south suburbs and the City of Chicago. The Assessor's calendar for 2026 says the south and west suburbs are being reassessed, and owners receive a Reassessment Notice with a new estimated fair market value when their township opens. Properties in the north suburbs and Chicago are reassessed in 2026 only if a permit, division of the parcel or other special circumstance changes them.

Each township has its own dates. For example, Proviso Township's notice was mailed September 14, 2026 and its Assessor appeal window ran through October 27, 2026, while River Forest had already closed its Assessor window on June 2, 2026 and opened Board of Review appeals from August 3 to September 1, 2026. Because the dates differ, find your township on the calendar before you plan.

An appeal contests the value, not the tax bill. Valid reasons include a belief that the market value is too high or that property characteristics, such as square footage, are wrong.

1. Look up your township's dates on the Assessor's calendar.
2. File with the Assessor's office within the township window.
3. If the result is unsatisfactory, file with the Board of Review in its later window.
4. After that, the state Property Tax Appeal Board or the courts are available.

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

The Cook County Clerk registers assumed names for individuals or spouses, partnerships and some professional corporations. LLCs and ordinary corporations do not register here.

1. Apply online (the system walks you through it), or download the form and bring it to the Vital Records office in the County Building at 118 N. Clark, Chicago.
2. Pay the $50 fee by card or e-check online, or by cash, check or money order in person.
3. Print the online application, have all owners sign before a notary, and deliver or mail it.
4. Publish the legal notice in a local newspaper within 15 calendar days of the registration date, once a week for three consecutive weeks.
5. Follow the Clerk's instructions for returning proof of publication.

The Clerk also runs a public search by business name, owner, address or registration number. Our assumed name guide compares counties.

What county taxes and licenses does Cook add?

The Department of Revenue administers taxes that have no counterpart in DuPage, Kane or Will. Its list includes the amusement tax, firearm and ammunition tax, gambling machine tax, gasoline and diesel fuel tax, hotel tax, liquor tax, new motor vehicle tax, non-retailer use tax, parking lot and garage operation tax, retailers' occupation tax, tobacco tax and use tax. Some, such as the county retailers' occupation tax, are collected together with the state's.

For sales tax, the regional transit tax rose by 0.25 percentage point in Cook and five other counties on August 1, 2026, and the state rate file now shows Cook County at 9.25% for general merchandise. The Cook portion of Elgin is 10.75%, while the Kane portion is 8.75%, so the county line through a single city changes the register rate. See the Illinois sales and use tax guide.

Licensing depends on the location:

• Unincorporated Cook County: a General Business License is required if you keep a fixed place of business, own or lease real property for business, or regularly keep stock for sale there. The fee is $40 per license for the period March 1, 2025 to February 28, 2027, with a $40 penalty for late purchase.
• Municipalities: your village or city licenses and permits you.
• Suburban health permits: the Cook County Department of Public Health issues permits and licenses for several environmental health programs, including retail tobacco; check with it or your municipality about food service.
• Recording: the County Clerk's Recordings Division records and maintains land records.

A worked example

Priya inherits a rental duplex in a south suburb and a coffee kiosk lease near a Metra station. She finds her township's reassessment notice (market value higher than expected), files with the Assessor by the township deadline, and keeps the Board of Review window as a backup. The kiosk is inside a village, so she follows the village's license rules, not the county General Business License.

Where can businesses get help?

The Illinois SBDC network lists centers including the Chicagoland Chamber, Harper College, Oakton Community College and College of DuPage. Our Illinois small business resources guide explains how to choose one.

Mistakes to avoid

• Applying a DuPage-style June and September calendar to a Cook bill.
• Ignoring the Assessor window and relying only on the Board of Review.
• Treating a village location as unincorporated and buying the wrong license.
• Forgetting that county line splits (like Elgin) change the sales tax rate.

How we can help

We are a CPA firm in the Aurora and Fox Valley area. For Cook County owners we handle the U.S. side: rental income, entity returns, Illinois sales tax and payroll, and bookkeeping, and we coordinate with your Canadian CPA or Indian Chartered Accountant when property or accounts abroad are involved. See real estate investor tax, sales tax and GST compliance and the Illinois compliance calendar.

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.