Cook County, IL: Property Taxes, Appeals and County Taxes Explained

Cook County is the largest county in Illinois and runs its property tax system differently from the collar counties around it. It has its own county assessor, a separate Board of Review, its own schedule for bills, and a set of county taxes that you will not find in DuPage or Will. This guide covers what a Chicago or suburban Cook County owner or business should know.

How Cook County differs

• A county assessor, not township assessors. Cook is one of only two Illinois counties where the county assessor has primary responsibility for valuing property.
• Classified property. Cook assesses different classes of property at different percentages of market value, instead of the one-third rule used in most counties.
• A rotating reassessment. The Assessor reassesses the county in three areas on a three-year cycle: the city, the north suburbs, and the south and west suburbs. In 2026 new values were released township by township in the south and west.
• A separate Board of Review. Appeals go first to the Assessor and then to the Board of Review, which publishes township-by-township filing dates and takes appeals online. After that, the Illinois Property Tax Appeal Board is the next level.

Installments and the shifting calendar

For tax year 2025, the Treasurer set the first installment for April 1, 2026 and the second for October 1, 2026. Cook's dates have moved in recent years: the second installment for tax year 2024 was not due until December 15, 2025. Do not assume last year's dates will repeat, and read the Treasurer's due dates page each spring.

Exemptions

Cook's Assessor lists homeowner, senior, senior freeze, persons with disabilities, returning veterans and veterans with disabilities exemptions. The state sets the general homestead maximum at $10,000 of assessed value in Cook, versus $8,000 in the neighboring counties. Exemptions appear as deductions on the second installment bill. If one is missing, you can file a Certificate of Error, and the Assessor's page shows the years that can still be corrected. The senior freeze requires household income of $65,000 or less for the 2025 assessment year, rising to $75,000 for 2026.

Cook County's own taxes

Cook's Department of Revenue administers several county taxes besides property tax. They include:

• The county retailers' occupation (sales) tax, collected together with the state tax and then passed to the county
• Use tax, hotel, amusement and parking lot and garage operation taxes
• Gasoline and diesel fuel, liquor, tobacco, firearm and ammunition, and gambling machine taxes

A regional transit tax is added on top. It rose by 0.25 percentage points on August 1, 2026, to 1.25% on general merchandise and 1.50% on qualifying groceries and drugs in Cook. Combined sales tax depends on the exact address, so use the state's tax rate finder, and see our sales and use tax service for businesses that sell across municipalities.

Cities and suburbs

Cook County includes Chicago, Schaumburg and many other northern and western suburbs. It also reaches into Elgin, Hinsdale and Woodridge, whose other parts lie in neighboring counties, so check which county your parcel is in.

How we can help

We can compare your exemptions against what Cook has on file, help decide between an Assessor appeal and a Board of Review filing, and place property taxes in context with the state and local tax deduction. For businesses, we prepare returns, run payroll and manage county and state sales tax filings. For decisions about a specific property, consult a qualified professional.

Frequently asked questions

General information only, not tax, legal or accounting advice for your situation. Rules, limits and deadlines change; confirm the current rules with the official source or a qualified professional before you act. Reading this page does not create a professional relationship with CPA Tax Payroll and Accounting Corp.