March 15, 2026
Cook County is home to over 5 million people and one of the most complicated property tax systems in the United States. If you own property in Cook County and you've never appealed your assessment, there's a good chance you're overpaying.
The Cook County Assessor's Office reassesses properties on a triennial (3-year) cycle. The county is divided into three groups of townships:
This means your township only gets reassessed every 3 years — but you can appeal every year if you believe your current assessment is incorrect.
After your reassessment notice arrives, you typically have 30 days to file an appeal directly with the Assessor. This is the first and most accessible level. The process is online and relatively quick.
If you're not satisfied with the Assessor's decision (or if you missed the Assessor deadline), you can appeal to the Cook County Board of Review. Each township has its own filing window, usually in the fall.
If you still disagree after the Board of Review, you can escalate to the state-level PTAB. This takes longer (often 1–2 years) but can be worth it for larger reductions.
The strongest evidence in Cook County appeals is comparable sales data — recent arm's-length sales of properties similar to yours. Specifically:
You need at least 3 good comps, ideally 5 or more. The more evidence, the better.
Successful Cook County appeals routinely reduce assessed values by 10–30%. On a home with a $10,000 annual tax bill, that's $1,000–$3,000 in savings per year.
Reductions are applied to the current tax year if you win at the Assessor or Board of Review level. PTAB decisions may result in refunds for prior years.
Missing the filing window means waiting for next year's cycle. Cook County is strict about deadlines — there are very few exceptions.
Overtaxed IL tracks filing windows automatically and alerts you when your township is open for appeals. We pull your comps, build your case, and file it — all you do is review and approve.