In Cook County the tax bill starts with a number the Cook County Assessor puts on your property — its assessed value. If that number is too high, or higher than comparable homes, you are paying more than your share. The fix is an appeal, and the county gives you two of them, for free, in order. The time to use them is a reassessment year, because that is when your value is freshly set — and for the City of Chicago, the next one is 2027.
The triennial cycle — why 2027 matters
Cook County does not reassess everyone every year. It runs a triennial cycle, reassessing one of three groups each year: the City of Chicago, the north and northwest suburbs, and the south and southwest suburbs. The City townships were last reassessed in 2024, which puts the next citywide reassessment in 2027. In the two years between, your assessment mostly holds; in the reassessment year the Assessor re-estimates market value from recent sales, and that is when values jump — sometimes sharply, unevenly across a block. So a reassessment year is both the year your bill is most at risk and the year an appeal has the most to work with.
Two free appeals, in order
1. The Assessor’s Office. When your township is reassessed you get a reassessment notice, and a roughly 30-day appeal window opens for that township. Windows open on a rolling schedule through the year, township by township, so the date is specific to where you live. This first appeal goes to the office that set the value.
2. The Board of Review. The Cook County Board of Review is a separate, independent body with its own appeal window that opens after the Assessor’s closes — and you can appeal to it even if the Assessor denied you or you never filed there. It is a genuine second bite, not a rubber stamp. Beyond the Board, the last resorts are the state Property Tax Appeal Board (PTAB) or the Circuit Court, but most residential cases are resolved at one of the first two levels.
The grounds that actually win
Lack of uniformity is the workhorse residential argument: comparable properties — similar size, age, class, and location — assessed at a lower value per square foot than yours. If five near-identical two-flats on your block are assessed below you, that gap is the case. Overvaluation is the other main ground: the Assessor’s market value is higher than the property would actually sell for, shown by a recent purchase price, an appraisal, or sales of comparable homes. And property-description errors — wrong square footage, the wrong number of units, a building that was demolished, the wrong property class — are the easiest wins of all, because they are simply facts to correct.
Exemptions are a separate, additive path
An appeal lowers the value; exemptions lower the taxable amount on top of it, and they are a different application. The Homeowner exemption, the Senior exemption, and the Senior Freeze each cut the bill for those who qualify, regardless of any appeal. Before you fight the value, make sure you are already getting every exemption you are owed — it is the fastest reduction available and easy to miss.
How to read your own number first
An appeal is only as good as the comparison behind it, so start with the record. Search your address above and Civic Worth resolves it to its Cook County PIN, its assessed value, and its appeal history — then lets you look at the neighbors you would cite. To see where appeals already cluster across the city, the appeal-rate map rolls the data up by community area; areas that appeal heavily are usually the ones where assessments and sales have drifted furthest apart.
Source: Cook County Assessor’s Office and Cook County Board of Review (public assessment and appeal process). Appeal windows, deadlines, and the reassessment schedule are set by those offices and change year to year — confirm the current dates for your township with the Assessor’s Office before filing.