After you file at the Assessor, your appeal waits until your township's filing window closes. Then an analyst compares your evidence with the property's record and with comparable sales, and the Assessor posts a decision on its website: a reduction, no change or, rarely, an increase where the record was wrong.
How long it takes
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. For the 2025 tax year the Assessor issued 244,942 decisions: the first in June 2025, about six in ten by the end of October, nine in ten by the end of November, and nearly all by December 31. Decisions come out township by township, so filing early does not move you up the queue.
The full timeline: How long does a property tax appeal take in Cook County?
If the result is not enough
Next is the Board of Review. It opens township by township after the Assessor certifies the township's values, and it takes a fresh look at the evidence rather than reviewing the Assessor's reasoning (see the Board of Review guide). After the Board, you can go to the state Property Tax Appeal Board (PTAB) or file a tax objection in the Circuit Court. The PTAB deadline is 30 days from the Board's written decision, or from the date the Board sends its final action on your township to the Assessor, if that is later (see the PTAB guide).
When the savings reach your bill
A reduction applies to that tax year whenever the decision comes. It shows on the second-installment bill, because the first installment is a flat 55% of last year's total. If you have already paid, the difference is refunded.
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