Rate Breakdown

Property taxes in Cook County are calculated by multiplying the assessed value (minus exemptions) by the total local millage rate.

How Property Tax Works in Cook County

The Cook County property tax system is driven by an annual assessment conducted by the Cook County Assessor’s Office. Every property owner receives an Assessment Notice that lists the assessed value, the taxable value (after exemptions), and the applicable millage rates. The assessed value is typically 70% of the market value for residential properties, though adjustments may apply for commercial or multistate holdings.

Millage rates are expressed in mills, where one mill equals one-tenth of a cent. Each county district—such as the school district, the Illinois State Bond Issue (ISBI), the Cook County budget, and the Cook County Optional Freeholders—adds its own millage. For example, a typical 2025 Cook County millage might total roughly 4.5 mills: 1.8 mills for the school district, 1.0 mill for the county budget, and 1.7 mills split between ISBI and the optional freeholders. The total millage multiplied by the taxable value (in thousands) yields the annual property tax bill in cents, which is then converted to dollars.

Available Exemptions

Illinois offers several exemptions that reduce the taxable value and, consequently, the annual bill. In Cook County, the most common exemptions include:

• Homestead Exemption: Provides a $1,000 reduction in assessed value for the owner’s primary residence.
• Senior Citizen Exemption: Grants a $1,000 or $2,000 reduction for homeowners aged 65 or older whose gross income does not exceed the state limit.
• Veteran Exemption: Affords a $1,000, $2,000, or $3,000 reduction for veterans based on disability rating or service status.
• Disability Exemption: Allows for additional reduction if the homeowner has a qualifying disability that limits their income or health.

To qualify, homeowners must file the appropriate exemption application through the Assessor’s Office each year. Missed deadlines typically result in a loss of the exemption for that tax year.

Payment Schedule & Deadlines

Cook County issues tax bills in three installments: the first due on the 10th day after the closing of the fiscal year (usually September 30), the second on December 15, and the third on March 15 of the following year. Property owners can choose to pay the full amount in one go, or split the payment into these three installments. Late payments incur penalties: a 1% late fee per month and a monthly interest charge of 9.9% annually.

Electronic payment options—such as the County’s online portal, mobile app, or phone banking—are encouraged to avoid missing deadlines. Remember that the collection process includes a garnishment option after 90 days of non‑payment, which can lead to a tax lien and eventually a forced sale of the property.

Appealing Your Assessment

Property owners who believe their assessed value is incorrect may file an appeal with the Cook County Board of Review. Applications must be submitted within 30 days of receiving the Assessment Notice. The appeal process involves a public hearing, submission of evidence (e.g., recent comparable sales, professional appraisals), and a decision by the Board. If the Board denies the appeal, the next recourse is to file with the Illinois Central Appellate Court, typically within 30 days of the Board’s ruling. Appeals can reduce taxable value, potentially saving significant amounts on yearly bills, so it is worth exploring this avenue if your property’s market value has changed or other factors justify a reassessment.