Three different bodies can decide a Cook County appeal, and they run on very different clocks. The Assessor decides after your township's window closes, usually within a few weeks to a few months. The Board of Review decides later the same assessment year, before second-installment bills are issued. PTAB cases often take two years or more.
What the county's own record shows
For the 2025 tax year the Assessor issued 244,942 decisions. The first arrived in June 2025. By the end of September roughly four in ten were out; by the end of October about six in ten; by the end of November nine in ten. All but a hundred were decided by December 31, 2025, and the busiest single month was November, with 72,961 decisions issued.
Two things about that wait surprise people. It is counted from when your township's filing window closes, not from the day you file — so filing early does not move you up the queue, though it does mean you cannot miss the date. And the decisions come out township by township rather than all at once, which is why two neighbors who filed the same week can hear back months apart.
The Board of Review
If the Assessor's answer is not enough, the Board of Review takes the case fresh — it is not an appeal against the Assessor's reasoning, it is a second look at the evidence. The Board opens township by township after the Assessor certifies that township's roll, so when your window falls depends on where the property sits. Our deadlines page tracks each township's dates as the county publishes them.
The Illinois Property Tax Appeal Board
PTAB reviews Board of Review decisions at the state level, and it is the slow route — a backlog measured in years rather than months. The clock to file, though, is short: 30 days from the later of the Board's written decision or the date the Board sends its final action on your township to the Assessor, not from the day the letter reaches you. Missing it is jurisdictional, so put the deadline on your calendar the moment the decision arrives.
Does waiting cost you anything?
No. A reduction applies to that tax year whenever the decision lands. If the bill has not been issued yet, it is calculated on the lower figure; if you have already paid, the correction comes back to you. The practical consequence of the timeline is not risk, it is patience — and that the moment to act is while your township's window is open, because once it closes the only routes left are the Board, the state board, or a Certificate of Error where the county's record is factually wrong.
Look up your property to see which window applies to it.