March 1, 2026
If your property tax bill feels too high, you're not alone. In Illinois — especially in Cook County — properties are routinely over-assessed. The good news: you have the right to appeal, and homeowners who appeal frequently win reductions.
Your property tax bill is based on your property's assessed value, not its market value. In Cook County, the assessment is supposed to be 10% of market value. In other Illinois counties, it's typically 33.3%.
When assessments are too high, you pay more than your fair share. That's exactly what an appeal corrects.
The county assessor mails assessment notices annually. When yours arrives, compare your assessed value to recent sale prices of similar homes in your neighborhood. If comparable homes sold for significantly less than the value your assessment implies, you likely have grounds for an appeal.
This is critical. Illinois property tax appeal deadlines are strict and vary by county and township. Missing the deadline means waiting another year.
Appeals in Illinois go to the Board of Review (county level) or the Property Tax Appeal Board (PTAB, state level).
For a Board of Review appeal you'll need:
The strongest appeals include recent sales of comparable properties — homes similar in size, age, and condition that sold for less than what your assessment implies. Overtaxed IL pulls this data automatically so you don't have to dig through county records yourself.
Board of Review decisions typically come within 3–6 months. If you win, your assessed value is reduced and your tax bill decreases — often retroactively for the current tax year.
A successful appeal can reduce your property tax bill by hundreds or even thousands of dollars per year. And unlike a lot of government processes, the bar isn't that high — you just need to show your home is assessed higher than comparable properties.
Overtaxed IL handles the entire process for you: finding comps, building your case, and filing on your behalf.