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Illinois has the highest appeal volume in the country, and you win on fairness rather than on sale prices.
We check individual addresses here. The winning residential argument here is uniformity: showing that homes genuinely like yours are assessed lower than yours is. We read 41 residential decisions from the Illinois Property Tax Appeal Board and 29 were uniformity cases, while only 6 even mentioned comparable sales. Cook County alone decided 133,526 house appeals in 2024.
So Illinois gives you a ground that runs on published assessed values rather than on sale prices. You're not showing what your house would sell for. You're showing that homes genuinely like yours are assessed lower than yours is, using numbers the county already publishes.
Now that matters more than it sounds, because it means a state keeping sale prices private doesn't stop you. Illinois, Texas, New York, New Jersey, Pennsylvania, New Hampshire, Kansas, Massachusetts and DC all have some version of it, and honestly it's usually the stronger argument even where sale prices are public.
Cook County runs township windows all year, and every homeowner gets a second free appeal at the Board of Review afterwards.
Miss it and you generally wait a year, so honestly the date matters more than the paperwork does.
And wherever you are, the single most useful thing you can actually do today is go find your assessment notice and read the date printed on it. That's what starts your clock, it's usually a much shorter window than people expect, and there's no getting it back once it's gone.
We've built pages for Cook County, with every township's live deadline, and Lake County, with every township's 2026 date. If you've just had a notice, start with our Cook County notice guide or our Lake County one.
First, look up your own record. Your county assessor's website shows your home's assessed value and the details it's based on, like square footage and age, and it's really worth checking those details are right. In Cook County it's 10 percent of market value, and everywhere else in Illinois it's one third, so multiply accordingly to see what the county really thinks your home's worth.
Next, know where to file. Cook County's different from everywhere else. You get two free appeals there, first at the Assessor when your township opens and then at the Board of Review. Outside Cook, you file with your county's Board of Review, usually within 30 days of the date your township's values were published in the newspaper. In both cases, if you don't win, you can still take it to the state Property Tax Appeal Board.
Then bring the evidence that wins here. Illinois mostly decides home appeals on fairness between neighbors. When we read 41 residential decisions from the state Property Tax Appeal Board, 29 came down to whether genuinely similar homes nearby were assessed lower per square foot. So the evidence that really counts is at least three comparable homes and their assessments, which are public.
Also, check your exemptions. The general homestead exemption takes $10,000 off your home's taxable value in Cook County and $8,000 in Lake County, and the senior exemption takes off another $8,000 in both if you're 65 or older. There's also a senior freeze for lower-income owners, and honestly it's easy to miss that you've got to apply for that one every year.
Cook County, including Chicago, and Lake County. Illinois decides these appeals on fairness between neighbors rather than on sale prices, so we compare what similar homes are assessed per square foot, which is the exact test the state appeal board applies. That ground needs no sale prices at all, and it is judged on clear and convincing evidence, which is a higher bar than a market value argument.
So type your address into our free check and we'll read the county's own records, work out whether the evidence actually supports an appeal, and tell you straight. Most people who use it get told not to bother, which is the point.
Check your Illinois home, free
We've screened all fifty states and DC on the same two questions. Does winning a lower market value actually lower your bill, or is there a cap sitting in between? And can you even put the evidence together from public records?
This comes from our own fifty-state screen, where we checked each state's cap, whether sale prices are public, whether there's an argument based on assessed values, and how many appeals actually get filed. Where we've quoted an appeal count, it's from the state or county that published it. If you spot an error, please write to hello@propertytaxbuddy.com and we'll correct it and say what changed.