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 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.
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
Also, there's one move that has nothing to do with appealing and that a lot of people miss entirely. Most states take exemptions off your bill before any of the value arithmetic happens, starting with a homestead exemption if you actually live in the house, and usually extra ones for owners over 65, for veterans, and for people with disabilities. They're often worth more than an appeal win, they carry forward year after year rather than needing to be re-won, and plenty of people who qualify have never filed for them. Your county assessor's website lists what's available where you live, and it costs nothing to look.
We 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 the evidence even be assembled from public records?
This comes from our own fifty-state screen, which checked each state's cap structure, whether sale prices are public, whether an assessment-based argument exists, and how many appeals actually get filed. Where we quote an appeal count it came 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.