Condominium assessments: your best comparables are in your own building
Units in one building share everything except floor, view and finish — which makes the comparison unusually clean.
Condominium owners have the easiest uniformity argument available to anyone, and most never make it. Your comparables are in your own building.
Why your building is the ideal comparison set
Every uniformity argument turns on whether the properties you are comparing against are genuinely comparable. In a condominium building that question answers itself: same construction, same year, same location, same amenities, same class code, often the same floor plan.
Nobody can argue your comparables are not comparable when they share a roof with you.
How condominium assessment works
The building is valued as a whole, and the value is allocated across units by their percentage of ownership — a figure fixed in the declaration and recorded with the county.
That produces two distinct things that can be wrong, and they need different arguments.
Error one: the allocation
Your percentage of ownership is a legal document. If the assessor's records show a different figure, your unit is carrying more or less of the building's value than the declaration says.
This is checkable in minutes: get the declaration, find your percentage, and compare it against what the county holds. A mismatch is a factual error and among the cleanest arguments in the entire system.
Error two: your unit against the others
Assemble a table of units in your building — PIN, floor area, percentage of ownership, and assessed value. Then compute assessed value per square foot, or assessed value per point of ownership percentage.
| Unit | % ownership | Assessed | $ per 1% |
|---|---|---|---|
| 3B | 1.24 | $29,800 | $24,032 |
| 4B | 1.24 | $29,900 | $24,113 |
| 5B (yours) | 1.24 | $34,100 | $27,500 |
| 6B | 1.26 | $30,400 | $24,127 |
Where a stack of identical units carries different assessments, the disparity is essentially impossible to justify — and this is exactly the pattern that appears when one owner appealed in a previous year and the others did not.
Where to find the PINs
In Cook County a condominium PIN ends in a non-zero unit segment — 1001, 1002 and so on — while the whole parcel ends 0000. Changing that last group walks you through the building unit by unit.
What the association can do
Nothing stops the board assembling the assessment data for every unit and circulating it. Where the whole building is over-assessed relative to comparable buildings, that is a collective finding — though each owner still files individually for their own PIN.
The exemption check first
As always. A condominium that is your principal residence carries the general homestead exemption, and it does not transfer from the previous owner. In a building with high turnover, a surprising number of units are missing it.