Home / Cook County / Your assessment notice
Your Cook County assessment notice isn't a tax bill, and it doesn't mean your bill is going up by the same amount. It's basically the Assessor telling you what they think your home's worth, and you've usually got about 30 days to disagree. Here's what each number on it means, how to tell if it's wrong, and what a reduction would actually be worth to you.
Most of the notice is honestly just reference information, like your PIN, your township, and your property class. Only three parts really matter.
Your home's details. The notice lists what the county has on file, like the square footage of the building and of the land, the age, and the class. The Assessor's own guidance says to appeal if any of those are wrong. A house recorded with 2,400 square feet when it's really 1,900 is a pretty easy fix, and it's exactly the kind of mistake that pushes a value up. But the Assessor also says a minor error doesn't necessarily mean your assessment's wrong.
The estimated market value. That's what the Assessor thinks your home would probably sell for. Your assessed value is 10 percent of it, so a home estimated at $350,000 would carry an assessed value of $35,000. It's the same 10 percent for every house in the county. The Assessor's rule of thumb is that if your details are right and the estimate's within 10 percent of what you think the home's worth, an appeal probably won't change your bill by much.
Finally, the date to file. It's printed on the notice, and it's usually 30 days after the notice was mailed. Filing with the Assessor is free, you can do it online, and the Assessor says it takes as little as 20 minutes. You really don't need to hire anyone.
Your bill's worked out in four steps, and the notice only gives you the first one. Here's how it works for a $350,000 home, using the 8 percent tax rate the Assessor uses in its own example. Your real rate's printed on your last tax bill.
| Step | Example |
|---|---|
| Assessed value, which is 10 percent of the estimated market value | $35,000 |
| Times the state multiplier. It was 3.0300 for 2025, set by the Illinois Department of Revenue | $106,050 |
| Minus your exemptions. The homeowner exemption takes off $10,000 | $96,050 |
| Times your local tax rate | $7,684 a year |
So that's why a higher value on your notice doesn't raise your bill by the same percentage. The tax rate is set separately by every school district, village and park district that taxes your home, based on how much money they ask for. If every home in your area went up by about the same amount, the rate usually comes down and your share stays pretty much where it was. What actually costs you money is your value going up more than your neighbors' did.
Say that $350,000 home wins a 10 percent cut in its assessed value. That's $3,500 off the assessed value, which works out to about $848 a year at the same 8 percent rate. And in Cook County a win usually holds until your township's next reassessment, which comes every three years, so a win early in the cycle can be worth roughly three times that.
But honestly, most appeals don't win. In 2024, 19.4 percent of Cook County house appeals that reached a decision got any reduction at all, out of 133,526 cases. So about 81 out of every 100 homeowners who appealed got nothing back for their afternoon.
Now Illinois has a quirk that most people probably don't know about. The Assessor's guidance talks about market value, meaning what your home would sell for. But when we read 41 residential decisions from the Illinois Property Tax Appeal Board, 29 of them were decided on uniformity, which just means whether homes genuinely like yours, nearby, are assessed lower per square foot than yours is. Only 6 even mentioned comparable sales.
So the real question is whether your assessment per square foot sits above the range for similar homes in your neighborhood. If it does, you have the case boards grant. If it's inside that range or below it, a board's basically going to look at the same numbers and change nothing, however expensive your home feels.
And that's exactly what our free check does. It reads the Cook County Assessor's own records, finds homes like yours in your assessment neighborhood, runs that per square foot comparison, and tells you which side of the line you're on. Most people who use it get told not to bother, and we'd rather tell you that before you spend the afternoon.
Check my Cook County home, free
Fortunately you've got a second try. After the Assessor's window closes, the Cook County Board of Review opens its own window for your township. It's a separate office with its own free filing, and it'll take the same evidence whether or not you appealed to the Assessor. Its evidence deadline falls ten days after its filing deadline, so you can file first and send the evidence after.
And if both windows close, the Assessor says you can appeal the following year when your township opens again.
Your township's printed on your notice, and the townships still taking appeals are listed first.
| Township | Assessor appeal | Board of Review appeal |
|---|---|---|
| Hyde Park | Open until 10/8/2026 | Not scheduled yet |
| Leyden | Open until 10/14/2026 | Not scheduled yet |
| Worth | Open until 10/15/2026 | Not scheduled yet |
| Wheeling | Open until 10/22/2026 | Not scheduled yet |
| Proviso | Open until 10/27/2026 | Not scheduled yet |
| Lake | Open until 10/29/2026 | Not scheduled yet |
| Palatine | Open until 11/4/2026 | Not scheduled yet |
| Orland | Open until 11/6/2026 | Not scheduled yet |
| Jefferson | Open until 11/12/2026 | Not scheduled yet |
| Schaumburg | Open until 11/19/2026 | Not scheduled yet |
| Bloom | Not on the calendar yet | Not scheduled yet |
| Hanover | Not on the calendar yet | Not scheduled yet |
| Niles | Not on the calendar yet | Not scheduled yet |
| North Chicago | Not on the calendar yet | Not scheduled yet |
| Rich | Not on the calendar yet | Not scheduled yet |
| South Chicago | Not on the calendar yet | Not scheduled yet |
| Thornton | Not on the calendar yet | Not scheduled yet |
| Barrington | Closed for this round | Not scheduled yet |
| Berwyn | Closed for this round | Closed 9/29/2026 |
| Bremen | Closed for this round | Not scheduled yet |
| Calumet | Closed for this round | Not scheduled yet |
| Cicero | Closed for this round | Closed 9/29/2026 |
| Elk Grove | Closed for this round | Closed 9/29/2026 |
| Evanston | Closed for this round | Closed 9/1/2026 |
| Lake View | Closed for this round | Closed 9/29/2026 |
| Lemont | Closed for this round | Not scheduled yet |
| Lyons | Closed for this round | Not scheduled yet |
| Maine | Closed for this round | Closed 9/29/2026 |
| New Trier | Closed for this round | Closed 9/1/2026 |
| Northfield | Closed for this round | Not scheduled yet |
| Norwood Park | Closed for this round | Closed 9/1/2026 |
| Oak Park | Closed for this round | Closed 9/1/2026 |
| Palos | Closed for this round | Closed 9/29/2026 |
| River Forest | Closed for this round | Closed 9/1/2026 |
| Riverside | Closed for this round | Closed 9/1/2026 |
| Rogers Park | Closed for this round | Closed 9/1/2026 |
| Stickney | Closed for this round | Not scheduled yet |
| West Chicago | Closed for this round | Not scheduled yet |
Also, exemptions take money off your bill without any appeal at all, and a missing one probably costs you more than most appeals would save. In the example above, the homeowner exemption alone is worth about $800 a year.
You can see which exemptions you're getting by looking up your PIN on the Cook County Assessor's website at cookcountyassessoril.gov.
The 10 percent assessment level, the rule of thumb, the 30 day window and the free online filing come from the Cook County Assessor's appeals page. The exemption amounts and rules come from the Assessor's exemption pages, and the 8 percent example rate is the one the Assessor uses there. The 3.0300 multiplier is the final 2025 Cook County equalization factor announced by the Illinois Department of Revenue on June 18, 2026. The state sets each year's multiplier the following year, so the one for 2026 isn't known yet.
Our win rate comes from the Assessor's published appeals dataset for tax year 2024, counting house appeals where the certified value came in below the mailed value. The 41 decisions are from the Illinois Property Tax Appeal Board at ptab.illinois.gov, and the uniformity rule is 86 Illinois Administrative Code 1910.63(e).
If you spot an error, please write to hello@propertytaxbuddy.com and we'll correct it and say what changed.