Property taxes in Illinois work through a three-step calculation: your county assessor estimates what your home is worth, a state multiplier adjusts that value to a common standard, and local taxing districts apply their combined tax rate to whatever is left after your exemptions. Understanding how property taxes work in Illinois means understanding those three levers, because each one can move your bill independently of the others. Illinois consistently ranks among the highest states in the country for effective property tax rates, and the money funds schools, libraries, parks, fire protection, and county government.
How Your Home’s Taxable Value Is Set
Everything starts with the assessor’s estimate of your home’s fair market value, based on recent sales of comparable homes, the size and condition of your property, and neighborhood trends. That market figure isn’t what you’re taxed on. In most of Illinois’s 102 counties, the assessed value is set at 33.33% of fair market value.1Illinois Compiled Statutes. Illinois Code 35 ILCS 200 – Property Tax Code, Title 3 A home worth $300,000 on the open market would have an assessed value of roughly $100,000.
Cook County is the exception. Residential homes there are assessed at 10% of fair market value rather than 33.33%.2Cook County Assessor’s Office. How Residential Property Is Valued The same $300,000 home in Cook County starts with an assessed value of $30,000, which is then adjusted upward by a much larger state multiplier to bring it into line with the rest of the state.
Assessors don’t revalue your property every year. Outside Cook County, general reassessments happen once every four years.3Illinois Department of Revenue. PTAX-1-A Introduction to Residential Assessment Practices Cook County runs on a triennial cycle, rotating through north suburbs, south and west suburbs, and Chicago.4Cook County Assessor’s Office. Assessment and Appeal Calendar Reassessment years are when values often jump, and when appeal activity spikes.
The State Equalization Multiplier
Because each county runs its own assessments, some end up higher or lower than the statewide 33.33% target. The Illinois Department of Revenue evens things out by assigning each county an equalization factor, commonly called the multiplier.5Illinois.gov. 2024 Cook County Final Multiplier Announced Counties assessing below the target get a multiplier above 1.0 to push values up. Counties assessing above the target get one below 1.0 to pull them down.
Your assessed value multiplied by the county’s equalization factor gives you your Equalized Assessed Value, or EAV. This is the number that actually drives your tax bill. Cook County’s multiplier is the largest in the state because residential property there starts at just 10% of market value. For 2024, Cook County’s final multiplier was 3.0355.5Illinois.gov. 2024 Cook County Final Multiplier Announced
Local Levies and the Tax Rate
Your EAV is the base. Stacked on top is the combined budgetary demand of every local taxing district that serves your address. A typical Illinois property sits inside a dozen or more overlapping districts: a school district, a community college district, a municipality, a park district, a library district, a fire protection district, a sanitary district, and the county itself. Each one files a levy, which is the dollar amount it wants to collect from property taxes for the coming year.
The county clerk adds up those levies, divides each by the total EAV in the district, and produces a tax rate. Your bill is your EAV (after exemptions) multiplied by that combined rate. This is why two homes with the same market value can carry very different bills if they sit in different taxing districts. A home inside a high-spending school district pays more than one just across the boundary in a district with lower levies.
A rising home value doesn’t automatically mean a higher bill. If local governments hold their levies steady while total EAV in the district rises, the rate drops. If your home’s value stays flat but a school district passes a new bond, the rate climbs and your bill goes up. The levy drives the bill more than the assessment does.
The PTELL Cap on Growth
Illinois limits how fast most local governments can increase their total tax take. The Property Tax Extension Limitation Law, known as PTELL or the “tax cap,” restricts non-home-rule taxing districts to annual levy increases of 5% or the prior year’s Consumer Price Index increase, whichever is less.6Illinois.gov. What Is the Property Tax Extension Limitation Law (PTELL)? Districts can exceed the cap only with voter approval through a referendum.
PTELL applies automatically to non-home-rule districts in Cook County and the five collar counties: DuPage, Kane, Lake, McHenry, and Will.7Illinois Department of Revenue. Property Tax Extension Limitation Law Technical Manual In other counties, PTELL takes effect only if voters adopt it by referendum. Home-rule municipalities and special service areas are exempt from the cap entirely, which is why tax bills in home-rule communities can climb more sharply. PTELL also caps only the total dollars a district can extend, not the rate on any single property, and revenue from new construction sits outside the cap.
Exemptions That Reduce Your Bill
Exemptions reduce your EAV before the tax rate is applied. Most aren’t automatic; you have to file an application with your county assessor’s office. To estimate the dollar savings from any exemption, multiply the EAV reduction by your local tax rate.
General Homestead Exemption
If you own and live in your home as your primary residence, you qualify. The reduction is up to $10,000 off your EAV in Cook County, up to $8,000 in the collar counties (DuPage, Kane, Lake, McHenry, and Will), and up to $6,000 in all other Illinois counties.8Illinois Compiled Statutes. Illinois Code 35 ILCS 200 – Property Tax Code, Title 4 Exemptions
Senior Citizens Homestead Exemption
Homeowners aged 65 or older get an additional EAV reduction on top of the general homestead exemption. The maximum is $8,000 in Cook County and the collar counties, and $5,000 elsewhere.9Illinois Department of Revenue. Property Tax Relief – Homestead Exemptions, PTELL, and Senior Citizens Real Estate Tax Deferral Program You qualify during the assessment year in which you turn 65.10Illinois General Assembly. Illinois Code 35 ILCS 200/15-170 – Senior Citizens Homestead Exemption
Senior Citizens Assessment Freeze
Separate from the senior exemption, the Assessment Freeze locks your home’s EAV at the level it was when you first qualified, as long as you keep meeting the requirements. For tax year 2026, total household income must be $75,000 or less; the cap rises to $77,000 for 2027 and $79,000 for 2028 and beyond.9Illinois Department of Revenue. Property Tax Relief – Homestead Exemptions, PTELL, and Senior Citizens Real Estate Tax Deferral Program The freeze applies only to your EAV, not to the tax rate, so your bill can still rise if local levies increase.
Homestead Exemption for Persons with Disabilities
If you have a disability that prevents you from working and is expected to last at least 12 continuous months or result in death, you can receive a $2,000 annual reduction in your EAV.11Illinois General Assembly. Illinois Code 35 ILCS 200/15-168 – Homestead Exemption for Persons with Disabilities You must occupy the property as your primary residence and be liable for the taxes. It stacks with other exemptions you qualify for.
Disabled Veterans Homestead Exemption
Veterans with a service-connected disability certified by the U.S. Department of Veterans Affairs receive EAV reductions scaled to the severity of the disability:12Illinois General Assembly. Illinois Code 35 ILCS 200/15-169 – Disabled Veterans Homestead Exemption
- 30% to 49% disability: $2,500 EAV reduction
- 50% to 69% disability: $5,000 EAV reduction
- 70% or greater disability: $250,000 EAV reduction, which effectively eliminates property taxes on most homes
Surviving spouses of veterans whose death was service-connected also qualify for the $250,000 reduction if they receive dependency and indemnity compensation from the VA. Veterans rated 100% permanently and totally disabled are automatically renewed each year.
Appealing an Assessment You Think Is Too High
If the assessed value on your notice looks too high, you can challenge it. Appeals are common in Illinois and frequently succeed, especially after a reassessment year.
Your first step is a written complaint to your county’s Board of Review. This is not optional; a Board of Review appeal is a prerequisite before you can take your case to the state Property Tax Appeal Board or circuit court.13Illinois Department of Revenue. Assessment Appeals – Property Tax The filing window opens after your township assessment roll is published, and you generally have 30 days from that publication date. Deadlines vary by township, so confirm with your county Board of Review.
Before filing, request your property record card from the assessor. It shows the details behind the valuation, including square footage, lot size, room count, and condition ratings. Factual errors on the card are the easiest wins. If the card lists a finished basement you don’t have, correcting that mistake alone may reduce your assessment.
For a formal appeal, gather documentary evidence: recent sales of comparable homes, copies of those properties’ record cards, photographs, and a professional appraisal if you have one. If you recently bought your home for less than the assessed value implies, bring your purchase contract or Real Estate Transfer Declaration. You can argue either that your home’s market value is lower than the assessor believes, or that your home is assessed unfairly compared to similar properties. A market value argument uses a preponderance-of-the-evidence standard; an unequal-treatment argument requires clear and convincing evidence, meaning several comparable properties showing a consistent pattern.14LII / Legal Information Institute. Illinois Admin Code Title 86 Section 1910.63 – Burdens of Proof
If the Board of Review denies your appeal or gives you an insufficient reduction, you have 30 days from its written decision to file with the state Property Tax Appeal Board.15State of Illinois Property Tax Appeal Board. Getting Started PTAB reviews independently and isn’t bound by the local board’s findings.
Billing, Payment, and What Happens If You’re Late
Illinois bills property taxes in arrears. The bill you receive in 2026 is for the 2025 tax year. In most counties outside Cook, the annual bill splits into two installments due around June and September. Lake County’s 2026 payment dates, for example, are June 4 and September 4.16Lake County, IL. 2025 Real Estate Tax Calendar (Payable in 2026) Cook County runs on a different schedule, with the first installment typically due in March and the second in August. The first installment is estimated at 55% of the prior year’s total, and the second reflects the actual calculated amount minus what you already paid.17Cook County Treasurer’s Office. Due Dates
Missing a deadline triggers penalties immediately. In most Illinois counties, unpaid taxes accrue interest at 1.5% per month, or 18% annually. Cook County charges a lower 0.75% per month for tax years 2023 and after.18Illinois General Assembly. Illinois Code 35 ILCS 200/21-15
When taxes stay unpaid, the county can sell the delinquent debt at a public tax sale. A third-party buyer pays your unpaid taxes and receives a tax certificate. This doesn’t transfer ownership, but it starts a clock. For residential properties of one to six units, you have at least two and a half years from the sale date to redeem by paying the buyer the taxes owed plus penalties. The buyer can extend the deadline up to three years. If you don’t redeem within that window, the buyer can petition a court for a deed to your property. If you’re struggling to pay, contact your county treasurer early. Some counties offer installment plans for delinquent taxes, and eligible seniors can apply for the state’s Real Estate Tax Deferral Program, which postpones payments until the property is sold.