Illinois Property Tax Guide 2025

Illinois has the second-highest property taxes in the nation, with an average effective rate of 2.23%. The median annual bill is about $5,100. Cook County (Chicago) uses a unique classification systemthat taxes residential properties at a lower ratio than commercial — but rates are still among the highest anywhere.

How IL Property Taxes Work

Illinois property taxes are among the most complex in the country. Your bill is determined by three factors:

1. Assessed value: In most of Illinois, properties are assessed at 33.33% of market value. Cook County uses a classification system (see below).
2. Equalizer (State Multiplier): The state applies a multiplier to ensure uniform assessment levels across counties. Cook County's multiplier is typically around 2.9-3.2x.
3. Tax rate: The sum of all overlapping taxing district rates (school, city, county, park, library, fire, etc.). A typical Cook County homeowner has 10+ taxing bodies.

Cook County Classification System

Cook County is the only county in Illinois that classifies properties:

• Residential (Class 2): Assessed at 10% of market value
• Commercial (Class 5a): Assessed at 25% of market value
• Industrial (Class 5b): Assessed at 25% of market value

After the state equalizer (~3.0x), the effective assessment ratio for homes is about 30% — lower than the 33.33% used in the rest of the state. This shifts more of the tax burden to commercial properties.

Effective Tax Rates by County

Lake County and Winnebago County have among the highest effective rates in the entire country.

Exemptions — Apply Every Year!

Critical: Most Illinois exemptions must be applied for or renewed. Many homeowners miss thousands in savings by not filing.

• Homeowner Exemption: Reduces EAV (equalized assessed value) by $10,000 in Cook County, $6,000 elsewhere. Must be primary residence. In Cook County, the assessor auto-applies if you filed once.
• Senior Homestead Exemption (65+): Additional $8,000 EAV reduction in Cook County, $5,000 elsewhere. Must reapply annually in most counties.
• Senior Freeze (PTELL): Freezes your EAV at the base year level if you're 65+ with household income under $65,000. Doesn't freeze your tax bill — only the assessed value. Must reapply every year.
• Disabled Person: $2,000 EAV reduction
• Disabled Veterans: $2,500-$5,000 standard; 70%+ disability gets sliding scale up to full exemption at 70%+ with income under $100,000
• Returning Veterans: $5,000 EAV reduction for the year of return from active duty
• Home Improvement Exemption: Up to $75,000 of improvements exempt from reassessment for 4 years

How to Appeal

Cook County

1. Cook County Assessor: File during your township's open appeal period (staggered by area — check the assessor's website). Online filing available. Free.
2. Cook County Board of Review: Second appeal. File after the assessor's decision. Also free. Can hire a tax appeal attorney (they typically take 33% of savings).
3. Property Tax Appeal Board (PTAB) or Circuit Court: Final options.

Other Counties

1. Board of Review: File within 30 days of assessment publication
2. PTAB: Appeal Board of Review decision within 30 days

Cook County tip: Appeals are extremely common — the system is almost designed for it. About 30-40% of appeals result in reductions. Use the assessor's comparable search tool to find similar homes assessed lower.

PTELL (Tax Cap Law)

The Property Tax Extension Limitation Law caps the annual increase in tax extensions (total levy) to 5% or the CPI increase, whichever is less. This doesn't cap your individual bill — if your assessment rises faster than average, your bill can exceed the cap even if total district revenue doesn't.

Key Dates

• January 1: Assessment date (lien date)
• Varies by township: Assessment appeals (Cook County — check assessor website)
• First installment: Due March 1 (55% of prior year's total in Cook County)
• Second installment: Due August 1 (balance after exemptions applied)
• Downstate counties: Typically June and September due dates