Property taxes are one of the most misunderstood — and most important — costs of homeownership in Illinois. As a broker working with buyers across Cook County and Lake County, I’m often asked how property taxes are calculated.
With the release of the 2024 Cook County Property Tax Rate Report and updated Lake County predominant tax rates, this is a good opportunity to break it down in plain English.
How Property Taxes Are Calculated in Illinois
At a high level, your property tax bill is driven by three factors:
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Assessed Value of the Property
Your home is assessed at a percentage of its market value (Cook County uses a classification system; Lake County uses a flat assessment percentage). -
Equalization Factor (State Multiplier)
This is applied to ensure assessments are uniform across the state. -
Local Tax Rate
This is where things differ — and where a lot of confusion comes from.
Tax Bill Formula (simplified):
Assessed Value × Equalized Factor × Local Tax Rate = Property Tax Bill
Two homes with the same value can have very different tax bills depending on where they are located.
Where Your Property Tax Dollars Go
A common misconception is that property taxes primarily fund state government. In reality, the majority of property tax revenue in Illinois goes to local school districts.
On average:
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Over 50% funds public schools
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The remaining balance supports:
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Municipal services
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Police and fire departments
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Libraries
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Park districts
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Local infrastructure
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Why Property Tax Rates Vary So Much by Community
Property tax rates are not uniform. They are set based on the budgets of local taxing bodies and the size of the tax base.
Factors that influence rates include:
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Number of overlapping taxing districts
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School district funding needs
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Commercial vs residential tax base
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Pension obligations
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Overall property values in the community
The result? Dramatic differences even between neighboring towns.
2024 Cook County Property Tax Rate Highlights
For a full breakdown of every Cook County taxing agency and applicable rates, the Cook County Clerk publishes a detailed annual report:
👉 2024 Cook County Property Tax Rate Report – All Taxing Agencies
The newly released 2024 report illustrates just how wide the range can be:
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Highest average tax rate:
Village of Phoenix – 34.39% -
Lowest average tax rate:
Burr Ridge – 6.59%
That means a $400,000 home in one community could carry a tax bill more than five times higher than a similarly priced home elsewhere.
2024 Lake County Predominant Tax Rates
Lake County also publishes an annual report outlining predominant tax rates by taxing district, which gives buyers visibility into how local agencies impact property taxes across different communities.
👉 2024 Lake County Predominant Tax Rates – All Taxing Agencies
Key highlights from the 2024 data:
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Lowest predominant tax rate:
Lake Forest – 5.98% -
Highest predominant tax rate:
Zion – 12.68%
Understanding the Homeowner’s Exemption (Lake County Example)
Many buyers are also unaware of how exemptions work and how their value differs by location.
In Lake County, the Homeowner’s Exemption reduces the Equalized Assessed Value by $8,000.
Estimated savings calculation: $8,000 × Local Tax Rate
Examples for 2024:
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Lake Forest (5.98%): Approximate savings: $478 per year
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Zion (12.68%): Approximate savings: $1,014 per year
The exemption is the same — but the benefit varies significantly depending on the tax rate.
What This Means for Homebuyers
Property taxes should never be an afterthought. Buyers should:
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Compare tax rates, not just home prices
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Understand how exemptions affect their bill
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Factor taxes into long‑term affordability, not just the first year
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Ask for the most recent tax bill, not estimates
Two homes with the same purchase price can have vastly different monthly costs once taxes are factored in.
Final Thoughts
Illinois property taxes are complex, hyper‑local, and often misunderstood — but they don’t have to be a surprise. With the right information, buyers can make smarter, more informed decisions about where they buy and what they can truly afford.
