Illinois Property Tax Guide for Homeowners: Understanding, Exemptions, and How to Appeal
Illinois property taxes are among the highest in the United States, and nowhere is this felt more acutely than in the Chicago south suburban corridor, where effective tax rates can reach 3%–4% of market value annually. For a homeowner with a $200,000 home in south Cook County, that can mean $5,000–$8,000 per year in property taxes — a cost that rivals or exceeds many homeowners’ mortgage principal payments. Understanding how Illinois property taxes are calculated, what exemptions you qualify for, and how to appeal an unfair assessment can save you hundreds or thousands of dollars per year. This guide covers the complete picture for Illinois homeowners.
How Illinois Property Taxes Are Calculated
Step 1: The Assessor Sets Your Assessed Value
Each Illinois county has an assessor (or assessment office) that estimates the value of your property for tax purposes. In Cook County, residential property is assessed at 10% of estimated market value. So a home the assessor estimates is worth $200,000 gets an assessed value (AV) of $20,000.
In the collar counties (Will, DuPage, Kane, Lake, McHenry), the assessment percentage is also set by state law at 33.33% of fair market value — but the state equalizer adjusts this downward, and the effective calculation differs from Cook County. Consult your county assessor’s website for the specific methodology in non-Cook counties.
Step 2: The State Equalizer Adjusts to EAV
The Illinois Department of Revenue publishes a State Equalizer (also called the multiplier) each year for each county. The equalizer adjusts assessed values to ensure counties across Illinois are taxed at consistent relative levels. In Cook County, the equalizer is typically around 2.9–3.0 (though this changes each year and is published annually by the state).
Your assessed value is multiplied by the equalizer to produce your Equalized Assessed Value (EAV). Using the Cook County example: $20,000 AV × 2.9 equalizer = $58,000 EAV.
Step 3: Exemptions Reduce Your EAV
Various homestead exemptions (covered in detail below) reduce your EAV before the tax rate is applied. If you qualify for the General Homestead Exemption ($10,000 EAV reduction in Cook County), your taxable EAV drops from $58,000 to $48,000.
Step 4: The Tax Rate Is Applied
Your taxable EAV is multiplied by the composite tax rate for your specific taxing district. This rate is the sum of all the individual rates set by each taxing body that applies to your address — your school districts (elementary and high school), the county, your municipality, the park district, the library district, the fire protection district, and other local taxing bodies. In Cook County south suburban communities, composite rates commonly range from 15% to 25% of EAV or higher in some areas.
Using our example: $48,000 EAV × 18% composite rate = $8,640 annual tax bill on a $200,000 home. This is why south suburban buyers are often surprised by property tax bills — the combination of high equalizer, multiple overlapping taxing districts, and comparatively constrained local school funding creates very high effective rates relative to home value.
Illinois Homestead Exemptions: Reduce Your Tax Bill
Illinois offers several exemptions that reduce your taxable EAV — and therefore your annual tax bill. These exemptions do not apply automatically in all cases; you must apply for most of them. New homeowners frequently miss exemptions in their first year because the prior owner’s exemptions do not automatically transfer.
General Homestead Exemption
The General Homestead Exemption reduces your EAV by $10,000 in Cook County (and varying amounts in collar counties) for owner-occupied primary residences. This exemption is available to any owner who occupies the property as their primary home. In Cook County, the $10,000 EAV reduction at an 18% composite rate saves approximately $1,800 per year. This is the single most important exemption for most Illinois homeowners — make sure it is applied to your property after closing.
Application: File with the Cook County Assessor’s Office (or your county assessor). In Cook County, the exemption typically renews automatically after the initial application — but verify with the assessor that it is appearing on your tax bill each year.
Senior Homestead Exemption
Homeowners 65 years of age or older qualify for the Senior Homestead Exemption, which provides an additional EAV reduction (currently $8,000 in Cook County) on top of the General Homestead Exemption. Income limits apply. The senior exemption must typically be renewed annually in most Illinois counties — watch for the renewal application and submit it each year to avoid losing the exemption.
Senior Freeze (Senior Citizens Assessment Freeze)
The Senior Freeze freezes the EAV on your home at the level it was in the year you first qualify, preventing assessment increases from raising your tax bill. It applies to homeowners 65+ who meet income limits (which are set at the state and county level). This exemption is particularly valuable in rising property markets — it caps the tax impact of appreciation for qualifying seniors. Annual renewal is required; income must be re-verified each year.
Home Improvement Exemption
The Home Improvement Exemption excludes up to $75,000 of added assessed value resulting from home improvements for a period of four years. If you add a room, renovate a kitchen, or make other significant improvements, the increase in assessed value from those improvements is excluded from your tax calculation for four assessment years. This exemption incentivizes property improvement without immediately penalizing owners with higher tax bills. Apply with the assessor after completing the improvement.
Veterans with Disabilities Exemption
Illinois provides property tax relief for veterans with service-connected disabilities, with EAV reductions ranging from $2,500 to full exemption (100% exemption for veterans with a 70%+ VA disability rating who meet additional criteria). Annual renewal is typically required. The Illinois Department of Veterans Affairs and your county assessor can provide current eligibility details.
Persons with Disabilities Exemption
Illinois also provides an EAV reduction for persons with disabilities who meet income requirements and use the property as their primary residence. Contact your county assessor for current eligibility details and application requirements.
How to Appeal Your Property Tax Assessment in Cook County
If your property’s assessed value appears higher than market value — which is common in Cook County, particularly in years following rapid appreciation — you have the right to appeal. The appeal process has multiple levels, each with different windows and procedures.
Cook County Triennial Assessment Cycle
Cook County reassesses properties on a triennial (three-year) cycle organized by township. Each year, roughly one-third of the county’s townships are in their reassessment year. When your township is reassessed, the Assessor’s Office mails a Notice of Proposed Assessment. This notice triggers your appeal window with the Assessor’s Office — a limited period during which you can challenge the new assessment. The window is typically 30 days from the notice date.
Know which township your property is in and when your township’s next reassessment is scheduled. The Cook County Assessor’s website publishes the reassessment schedule. Being prepared before your notice arrives gives you time to gather comparable sales evidence rather than rushing to meet a deadline.
Level 1: Cook County Assessor’s Office
The first appeal opportunity is with the Cook County Assessor’s Office during the reassessment period for your township. This is an informal review — you submit evidence (typically comparable sales) and the Assessor’s Office reviews and may adjust your assessment. Online filing is available at the Cook County Assessor’s website. This is the easiest and fastest appeal level.
Level 2: Cook County Board of Review
If you are unsatisfied with the Assessor’s result (or missed the Assessor’s window), the Cook County Board of Review is the primary appeal venue. The Board of Review is a separate, quasi-judicial body with three elected commissioners. They hear appeals after the Assessor’s Notice is issued and before the tax bills are generated.
The Board of Review appeal requires submitting:
- A completed appeal form (available on the Board of Review website)
- Evidence of market value — typically three to six comparable sales of similar properties that sold in the prior 12–18 months at prices below what your assessed value implies
- A uniform property description form for your property
The window for Board of Review appeals opens annually (not just in reassessment years) and closes at a published deadline. You can appeal to the Board of Review each year, not just when your township is being reassessed — but the best opportunities often come in reassessment years when new values are issued.
Many Cook County property owners use tax attorneys or property tax consultants to prepare and file Board of Review appeals. These professionals typically work on contingency — they receive a percentage of the tax savings if the appeal is successful, with no fee if it is not. For properties with significant tax bills, professional representation often produces better outcomes than self-representation.
Level 3: Illinois Property Tax Appeal Board (PTAB)
If you receive an unsatisfactory result from the Board of Review, you can appeal to the Illinois Property Tax Appeal Board (PTAB) — a state agency that hears property tax assessment appeals. PTAB appeals are more formal, can take 12–36 months to resolve, and typically require more extensive evidence preparation. PTAB is most cost-effective for larger commercial properties or residential properties with very large assessment disparities. Many residential owners do not proceed to PTAB unless they have significant tax exposure at stake.
Level 4: Illinois Circuit Court
The final appeal level is the Illinois circuit court, where you can challenge the assessment as a legal matter. This level is almost exclusively used by large commercial property owners due to the cost and complexity of litigation. For residential properties, the Board of Review and PTAB are the practical appeal venues.
Building Your Appeal: Comparable Sales Evidence
The strongest basis for a residential property tax appeal in Illinois is comparable sales evidence — documented sales of similar properties that demonstrate your home is assessed higher than its fair market value. When building comparable sales evidence:
- Identify three to six sales of properties similar to yours (similar size, age, construction type, location) within the prior 12–18 months
- Calculate the implied assessed value for each comparable (sale price × 10% for Cook County)
- If those implied assessed values are significantly lower than your actual assessed value, you have a case
- MLS data, the Cook County Assessor’s property database, and public sales records are all sources for comparable sales
- Your real estate agent can pull comparable sales data — this is one of the most practical uses of an agent relationship even outside a transaction
Will County and Collar County Property Taxes
Will County and other collar counties (DuPage, Kane, Lake, McHenry) use a similar structure but with key differences:
- Assessment percentage: Assessed at 33.33% of fair market value (versus 10% in Cook County) — but the equalizer for collar counties adjusts this, typically producing a lower EAV relative to market value than Cook County
- Effective rates: Generally lower than Cook County south suburban rates, though specific rates vary significantly by taxing district — some Will County communities have very low composite rates, others higher ones due to school district funding needs
- Annual reassessment: Unlike Cook County’s triennial cycle, most collar counties reassess annually or on different schedules — check your county assessor’s office for specifics
- Appeal process: Similar structure — Assessor, Board of Review, PTAB — with county-specific procedures and deadlines
Property Taxes and Your Home Purchase Decision
When evaluating a home purchase in the South Suburban Chicago market, do not rely on tax estimates or statewide averages. Get the actual current annual tax bill for every property you seriously consider. The differences can be substantial:
- Two comparable $200,000 homes can carry tax bills that differ by $2,000–$4,000 per year depending on which taxing districts overlap the specific parcel
- A home just outside a high-spending school district’s boundary may have significantly lower taxes than an identical home just inside it
- Prior owner exemptions do not transfer — your first-year tax bill may be higher than the prior owner’s until you apply for your own exemptions
- Reassessment years can produce significant jumps in assessed value — particularly if values in your area rose significantly in the prior three years
Your lender will use the current tax bill to calculate your escrow requirement. Make sure the tax information in your purchase contract and loan estimate reflects the actual current bill, not an estimate based on prior-year data.
Working With Krembo Group on Property Tax Questions
Krembo Group helps South Suburban Chicago buyers understand property tax obligations as part of every transaction — pulling current tax bills, explaining assessment districts, and flagging situations where a post-closing appeal may be warranted. We can also connect buyers and homeowners with reputable property tax appeal consultants who work on contingency for Cook County appeals. Contact us with any questions about property taxes in the communities we serve.
Contact Krembo Group with your property tax questions →
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