Chicago’s assessment roll opened at $49.46 billion last year. By the time the Assessor and the Board of Review had both ruled, $3.85 billion of it was gone.
Cook County Assessor records, 2025 tax year · all 882,741 parcels in the eight Chicago assessment townshipsThe interesting question is who it went to, and the answer is lopsided enough to be worth a careful look. Setting aside the parcels that carry a development incentive, whose reduction is written into law rather than won on appeal, Commercial and industrial property holds 39% of Chicago’s assessed value. It collected 86% of the reductions. Residential property holds 51% of the value and collected 9%.
There is an obvious objection to that chart, and it is a good one: commercial property is assessed differently from a house, so maybe the shares are just an artifact of how the arithmetic works. So here is the same finding with that particular objection removed. Commercial property had 17.0% of its own assessed value taken off. Residential had 1.3%. Not a share of the city total, a share of each class’s own value, which is a comparison the different assessment levels cannot explain away. Thirteen to one, on the same roll, in the same year. It does not tell you the two classes were assessed equally accurately to begin with, and nothing here can.
Was last year strange?
| Tax year | Residential cut | Commercial cut |
|---|---|---|
| 2021 | 4.7% | 35.0% |
| 2022 | 1.7% | 21.5% |
| 2023 | 1.2% | 17.5% |
| 2024 | 3.0% | 23.1% |
| 2025 | 1.3% | 17.0% |
No. Five years, same shape, never close. In 2021 commercial property shed just over a third of its assessed value on appeal while residential shed under five percent. The gap narrows and widens; it never reverses, and it never gets small.
Where it happens, which turns out to matter
Cook County has two places to bring an assessment challenge. The Assessor takes them first, and the Board of Review takes them afterwards, whether or not the owner went to the Assessor at all. Split the reductions by stage and the two classes look nothing alike. Commercial property lost 2.9% of its value at the Assessor and 14.0% at the Board. Residential lost 0.6% and then 0.7%. About four fifths of the commercial reduction, the part that moves billions, happens at the second stage, in front of the Board of Review.
Why this is not free money
Illinois does not set a property tax rate and multiply. It works the other way around. Each taxing district decides what it needs to collect, and the rate is that number divided by the total taxable value inside the district. Hold that levy still and the arithmetic closes on itself: value taken off one property does not evaporate, it is picked up by the rest of the district through a higher rate. Real bills are messier than that, because levies move, caps bite, new construction enters the roll and TIF districts divert part of it. Those things blur the arithmetic without reversing it. To the extent a district collects a set amount, a reduction is not a discount that comes from nowhere. It is a transfer, and somebody is on the other end of it.
The counter-argument, which is real
Before anyone reaches for a pitchfork, the honest version of this story has a second half. Homeowners in Cook County get relief through an entirely different door, and it is one commercial property cannot use. The homeowner exemption takes $10,000 off the equalized assessed value of an owner-occupied home, and it is applied after appeals rather than instead of them. An owner has to claim it once; after that the Assessor renews it every year without being asked, so it arrives without anyone arguing for it.
That matters enormously for reading the numbers above. Residential property may appeal less because it already receives a large, automatic reduction that never appears in an appeal file. Commercial property has no equivalent standing exemption, but it is not without other routes either. Some commercial and industrial parcels carry an incentive classification, which sets a lower assessment level in statute so the reduction is built into the value before anyone appeals anything. We excluded those parcels from every figure on this page precisely because that relief is granted by law rather than won, and this file cannot size it. So this is not one door and one wall. It is different doors for different owners, and the appeal is the one commercial property leans on hardest. Some of the gap here is that structural difference rather than anybody outmaneuvering anybody.
So what is actually established here?
- On the recordChicago’s 2025 roll, all 882,741 parcels, opened at $49.459 billion in assessed value and closed at $45.605 billion, a reduction of $3.854 billion. Excluding incentive parcels, the comparable figures are $48.725 billion, $44.981 billion and $3.744 billion.
- On the recordCommercial and industrial property is 39% of the city’s assessed value and received 86% of the reductions. Residential is 51% of the value and received 9%.
- On the recordMeasured against its own value, commercial property was cut 17.0% and residential 1.3%. That holds in all five years we examined.
- On the recordAbout four fifths of the commercial reduction happens at the Board of Review, the second stage, rather than at the Assessor.
- On the recordIllinois sets rates by dividing a district’s levy by its total taxable value, so for a fixed levy, value removed from one property is carried by the others.
- On the recordThe homeowner exemption removes $10,000 of equalized assessed value for an owner-occupant, claimed once and renewed by the Assessor thereafter, with no equivalent for commercial property. Residential relief therefore runs substantially through a channel these figures do not contain.
- Not establishedThat commercial owners did anything improper. Every reduction here was granted by a public body applying its own rules, but this file records outcomes, not conduct, and cannot vouch for what any filer submitted.
- Not establishedHow much of the gap is the structural difference between the channels and how much is the appeal process itself. That needs parcel-level exemption data for the same year, and the only such file we located in the county catalogue was archived in 2022.
- Not establishedWhat any of this did to an individual tax bill. Rates vary by district and the levy moves too, so a change in the roll does not map cleanly onto what landed in anyone’s mailbox.
Which leaves a question worth sitting with rather than answering too quickly. If the automatic route is open to one kind of property and not the other, and if the filing route moved $3.23 billion last year while the automatic one takes the same $10,000 off the equalized value of a bungalow and a mansion alike, then the two doors are not the same door. One scales with the value of what you own. The other is a fixed amount that does not. Whether that is a fair design is a political question, and it is a different question from whether anyone broke a rule. This data cannot answer the second one either way. What it shows is a system working as written, which is the more uncomfortable finding of the two.
How we counted
- Source: the Cook County Assessor’s Assessed Values file (uzyt-m557), which carries every parcel rather than only the appealed ones, with the Assessor’s opening value, the value after its own appeal stage, and the value after the Board of Review. The Assessor divides the City of Chicago into eight assessment townships, codes 70 to 77, and those are what we used: 828,727 parcels for the 2025 tax year. We checked by mapping that all eight fall inside the city. Where this page says Chicago, it means those eight townships.
- Two parcel counts appear on this page, deliberately. The roll totals cover all 882,741 parcels in the eight townships. The class-by-class comparison drops the 54,014 parcels that hold a Class 6, 7 or 8 incentive, leaving 828,727. Under the county’s classification rules those parcels are assessed at a lower level than ordinary commercial property as economic development. That reduction is built into the value before any appeal, so it is relief granted by law rather than won at a hearing, and mixing it in would overstate what the appeal process itself does. This file records assessed values, not assessment levels, so we cannot size the incentive benefit and have not tried.
- Both stages are counted, and reported separately. Reductions between the mailed value and the certified value are the Assessor’s; reductions between certified and board are the Board of Review’s. Collapsing them into one number hides that commercial relief is overwhelmingly a second-stage event.
- These are assessed values, not market values and not tax bills. Assessment levels differ by class in Cook County, which is exactly why the central comparison on this page is each class against its own value rather than against the others. Note also that tax rates are struck against EQUALIZED assessed value, after the state multiplier is applied, and these figures are pre-equalization assessed values. The multiplier is county-wide, so it does not move the comparisons here, but it does mean none of these numbers is a tax bill.
- This measures the appeal channel only. Exemptions are applied after appeals and do not appear in these fields. Searching the county open-data catalogue on July 19, 2026 the only parcel-level exemption file we could find was an archived one last updated in 2022. There may be a current source we did not locate; what we can say is that we did not find one, so we have not tried to size that channel.
Computed by KCM Desk from Cook County Assessor records for the 2025 tax year; published July 19, 2026. If you spot an error, corrections come first.