Property taxes in Cook County explained

This guide is for Cook County homeowners who opened a tax bill or a reassessment notice and want to know what drives the number, and for anyone buying in the city or suburbs who wants to understand the system before closing. It covers how the Assessor sets values, the exemptions people most often miss, how to appeal, when your part of the county is reassessed, and how the collar counties handle the same job differently.

The short version: your bill depends on your assessment, everyone else’s assessment, the exemptions on your property and the budgets of the local taxing bodies that levy on it. You can only influence the first and third directly, and both are free to work on.

How the assessment works

Five offices touch your bill. The Cook County Assessor estimates market value. The Cook County Board of Review hears appeals and finalizes values. The Illinois Department of Revenue sets a county-wide equalization factor. The Cook County Clerk calculates tax rates, and the Cook County Treasurer mails the bills and collects the money. The Assessor lays this out on its property tax system page.

From market value to tax bill

According to the Assessor’s explanation of the notice and bill, residential property is assessed at 10% of the estimated fair market value, and most commercial property at 25%. The state equalizer is multiplied against that assessed value to get the equalized assessed value, or EAV. Exemptions come off the EAV, and what is left is multiplied by the local tax rate.

The tax rate is where most confusion starts. Rates are set by dividing what schools, the city or village, parks, libraries and other districts levy by the total assessed value in the area. If your value rises less than your neighbors’ values, your share of the levy can shrink. If the levies go up, your bill can rise even when your assessment stays flat.

Why your bill has two parts

Each tax year is billed the following year in two installments. The Assessor notes that by law the first installment is exactly 55% of the prior year’s total bill. The second installment carries the new assessment, exemptions and tax rates, so that is the bill that jumps or drops. A reassessment notice you get in 2026 shows up on the second installment mailed in 2027.

Exemptions you may be missing

Exemptions reduce EAV, not your bill dollar for dollar. Your actual savings equal the exemption amount multiplied by your local tax rate. The Assessor lists all of them on its exemptions page. For the current tax year (2025, billed in 2026), the amounts are:

• Homeowner Exemption: $10,000 off EAV if you own or are responsible for the taxes on your principal residence. The Assessor estimates average savings at about $950 a year. Renews automatically.
• Senior Exemption: $8,000 off EAV for owners 65 and older who live in the home. Renews automatically.
• Senior Freeze: holds EAV steady for seniors with household income of $65,000 or less in 2024. The freeze does not stop the bill from moving if rates change, and you must reapply every year.
• Persons with Disabilities Exemption: $2,000 off EAV, with proof such as a Class 2 Illinois Disability ID or a Social Security disability award letter.
• Veterans with Disabilities Exemption: $2,500 off EAV for a 30% to 49% service-connected rating, $5,000 for 50% to 69%, and $250,000 for 70% or more, which can wipe out the tax on a home. Most veterans reapply yearly; those rated 100% and permanently and totally disabled now renew automatically.
• Home Improvement Exemption: shields up to $75,000 of added value from an addition or major repair for up to four years. No application. The Assessor picks it up from building permits.

The Longtime Homeowner Exemption is narrower. The Assessor says only about 2% of county homeowners qualify, and it mails applications to properties that might.

How to catch a missed exemption

Look at the exemptions section of your second installment bill first. The Treasurer’s exemption history search shows what has been applied by PIN. The Treasurer’s home page currently flags $19 million in missing senior exemptions going back four years and $105 million in available refunds. If something is missing, the Assessor processes late filings as Certificates of Error, and the office currently accepts them for tax years 2021 through 2025. New buyers are the most common gap: the prior owner’s exemption does not carry over.

Appeals: when and how

Appeals are free at every level, and you do not need a lawyer to appeal your own house or condo. There are three stops.

1. The Assessor

You usually have 30 days after your township’s reassessment notices are mailed, and the exact last day is printed on the notice. The Assessor’s residential appeals page recommends filing online. Useful evidence includes a recent closing statement, sales of similar homes, comparable homes in your assessment neighborhood with lower values, and proof of wrong characteristics such as square footage. Appraisals must follow USPAP standards. The Assessor’s own appeals overview says that if the characteristics are right and the market value is within about 10% of what you think the home is worth, an appeal probably will not move the bill much.

2. The Board of Review

The Board of Review opens townships in groups, each for at least 30 days, and you can file there whether or not you appealed to the Assessor. The Board’s FAQ says filing is free, staff will help, and photos of the property are required. You can represent yourself on your own condo, small apartment building, mixed-use building or family business property held in your name. A corporation needs an attorney.

3. The state board or the courts

If the Board of Review decision still looks wrong, the Illinois Property Tax Appeal Board takes appeals filed within 30 days of the postmark on the decision notice, with no filing fee, according to its FAQ. The other route is a tax objection in Cook County Circuit Court. Either way, your taxes still come due while the appeal is pending.

When to hire help

Most homeowners can handle an Assessor or Board of Review appeal alone. Larger buildings, commercial property and PTAB cases are where attorneys earn their fees, and a corporate owner has to use one at the Board of Review. Two Loop firms that concentrate on property tax work, both at 100 N. LaSalle St. near the Washington/Wells and Clark/Lake stations:

• The law firm Sarnoff Property Tax has handled real estate tax appeals in Cook County since 1986 and also works in Lake, Will, DuPage, Kane and McHenry counties. Sarnoff offers free consultations through an online form.
• The firm Rieff Schramm Kanter & Guttman handles property tax appeals, abatements and eminent domain for commercial, industrial and residential owners, and posts regular updates on Cook County bill dates and multipliers on the firm’s blog.

Neither firm publishes its fees, so ask how they are calculated before you sign.

The reassessment cycle

Cook County reassesses one third of the county each year, per the Assessor’s system overview:

• City of Chicago: 2024 and next in 2027
• North suburbs, including Evanston, Palatine and Schaumburg townships: 2022 and 2025
• South and west suburbs, including Berwyn, Cicero, Oak Park and Lemont townships: 2023 and 2026

So 2026 is the south and west suburbs’ turn. Homeowners in places such as Berwyn and Cicero are getting new values this year, and those values reach the second installment bill in 2027. Chicago and the north suburbs are only reassessed this year for properties with significant changes, but those townships still open for appeals on their own schedule.

A reassessment year is the best time to appeal, because the new value typically carries forward until the next reassessment unless you appeal again. In the two years between, you can still appeal when your township reopens, but the evidence has to show the value is wrong now.

Collar counties compared

DuPage, Lake, Will, Kane and McHenry counties run a different system, which matters if you are weighing a move across the county line.

• Who assesses: elected township assessors set the first values, and each county’s supervisor of assessments reviews them. DuPage has nine township assessors, per its Supervisor of Assessments.
• Assessment level: the state standard is one-third of market value, compared with Cook’s 10% for homes before the equalizer. Assessed values across the line are not comparable. Compare actual bills instead.
• Cycle: general reassessments run every four years. DuPage’s assessment cycle page lists 2019 and 2023 as general assessment years, which puts the next one in 2027.
• Appeals: the window is 30 days after the township assessment roll is published, and appeals go to the county Board of Review. In DuPage, written decisions usually go out the following March, per the county’s appeal process page.
• Exemptions: the general homestead exemption is $8,000 of assessed value in counties bordering Cook, compared with $10,000 in Cook. The senior exemption is $8,000 in both, according to the Illinois Department of Revenue’s property tax relief page. In DuPage, township assessors usually grant the homestead exemption without an application.

Good to know

Checked September 28, 2026. Dates below come from the Assessor’s 2026 assessment calendar, the Board of Review’s 2026 township schedule and the Treasurer’s due dates page.

• The tax year 2025 second installment is due Thursday, October 1, 2026. The first installment was due April 1, 2026.
• Assessor appeal deadlines still ahead: Calumet Township on October 2, Hyde Park on October 8, Leyden on October 14, Worth on October 15, Wheeling on October 22, Proviso on October 27, Lake on October 29, Palatine on November 4 and Orland on November 6. Lemont’s window closes September 29. Thornton, Rich and Bloom notices had not been mailed as of this check.
• At the Board of Review, the second group of townships (Berwyn, Cicero, Elk Grove, Lakeview, Maine and Palos) closes for filing on September 29, 2026, with evidence due October 9.
• The Senior Freeze income limit rises from $65,000 to $75,000 starting with tax year 2026, billed in 2027, under Public Act 104-0452, per the Will County Supervisor of Assessments and the Illinois Department of Revenue.
• The Assessor’s office is at 118 N. Clark St. in the Loop, a short walk from the Clark/Lake stop on the Blue, Brown, Green, Orange, Pink and Purple lines. Street parking downtown is metered and scarce; mailing or filing online saves the trip.

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