From tax year 2010 through tax year 2025, the Cook County Board of Review issued 2,393,726 decisions on houses and townhouses. It lowered the value on 1,353,318 of them (56.5%). It raised the value on 72. That is about 1 in 33,000.
For owners who filed their own house appeals, the record is 757,403 decisions and 20 increases.
So the Board can raise a value. It almost never does on a house, and the law requires a warning before it can. Here is what the rules say, what the record shows, and the few situations where you should look twice before filing.
Quick Answer
Yes, the Cook County Board of Review has the power to raise an assessment, but state law says it cannot raise yours until you have been told in writing and given a chance to be heard. In practice, increases are rare. Across 16 tax years, 72 of 2,393,726 house and townhouse decisions went up. Nearly all increases on residential property were condo units in building-wide appeals. Fear of an increase is not a good reason to skip an appeal. A purchase price well above the county's value, or a county record that undercounts your home, is a good reason to check first.
What the rules say
The Board can move a value either way. The Board's own description of its powers says it can order the Assessor to raise or lower an assessment, but only after finding that the assessment is wrong.
You get notice before any increase. Illinois law for Cook County says the Board may not raise a taxpayer's assessment unless the taxpayer has first been notified in writing and given an opportunity to be heard. When the Board changes a value on its own motion, the owner and the Assessor must both be notified first.
Others can ask for a higher value, whether or not you file. A school district or other taxing district, or another taxpayer, can file a complaint that a property is under-assessed. The Board calls these intervenor complaints. Its intervenor rules require the filer to notify the owner of record, send the owner its evidence, and give notice of the hearing. Your own appeal is not what opens that door. It exists either way.
Withdrawing is not spelled out. The Board's published rules do not describe a step for an owner to withdraw a complaint once filed. They do say that if you file a second complaint yourself on the same PIN, the later one controls, and that a complaint filed by an attorney controls over later ones. If you have filed and want to stop, call the Board's office before your hearing and ask how.
Filing is free, and hearings are optional. The Board's FAQ says filing is free. It also says you will not be penalized for waiving a hearing, and that files with and without hearings get the same review.
The record: 16 tax years of Board decisions
PIN-level Board of Review decisions, tax years 2010 through 2025:
| Property | Decisions | Lowered | No change | Raised |
|---|---|---|---|---|
| All property | 6,933,428 | 46.1% | 53.8% | 5,111 (0.07%) |
| All residential | 5,756,227 | 48.7% | 51.2% | 4,459 (0.08%) |
| Houses and townhouses | 2,393,726 | 56.5% | 43.5% | 72 |
| Houses, owner-filed | 757,403 | 64.3% | 35.7% | 20 |
| Condo units | 2,810,234 | 42.9% | 56.9% | 4,350 (0.15%) |
| Two- to six-unit buildings | 497,012 | 47.9% | 52.1% | 15 |
Recent years look the same. In tax year 2024 the Board issued 490,231 residential decisions and raised 90. In tax year 2025 it issued 447,784 and raised 67.
Where the rare increases come from
Condo buildings, mostly. Of the 4,459 residential increases, 4,350 (97.6%) were condo units. They came from 327 complaints, most of them building-wide filings, and 4,200 of those units were in attorney-filed complaints. In those same complaints, 8,366 units were lowered and 4,350 were raised. In 263 of the 327 buildings, the total value still went down. When the Board revisits a whole building, some units can move up while the building as a whole comes down.
One year stands out. Tax year 2021, Chicago's reassessment year, produced 3,531 condo unit increases from 225 building complaints, all in the city's eight townships. For most of them the Board's stated reason was its condo analysis. In 220 of those 225 buildings, total value went down.
Houses: a handful, often record fixes. Of the 72 house and townhouse increases in 16 years:
- 17 were under 1%, and 9 were $10 or less of assessed value.
- 14 carried the Board's reason for a value backed by an Assessor recommendation, a restored earlier value, or an earlier decision.
- 16 were townhouses decided with the Board's condo analysis.
Some fall in more than one group. Of the 20 owner-filed house increases, 12 carried that record-correction reason, and 3 started from an Assessor value of $0. Several look like records being corrected, not penalties for filing.
When to look twice before filing
You bought recently, for well above the county's value. The Board's rules require you to disclose your purchase price if you bought within three years of the assessment date. If you paid much more than the Assessor's market value, your own closing papers point the other way. An overvaluation appeal is a weak fit. A uniformity argument may still work. Our guide to overvaluation versus lack of uniformity explains the difference.
Your county record undercounts your home. The Board is not limited to what you send. Its own description says it may act on information from other sources. If the record is missing an addition or a finished living area, fixing it could move the value up, not down. Check your property record first. Our guide to property record card errors shows where to look.
You own a condo in a building that files together. Building-wide filings can move individual units both ways, as the 2021 numbers show. The Assessor's rules let condo owners opt out of an association filing and file for their own unit. See condo association appeals.
You get a notice about a possible increase. Read it and respond. You have the right to be heard before any increase.
What to do
- Look up your PIN on the Assessor's site and check the property details: square footage, bedrooms, basement, garage.
- Compare the Assessor's market value with what similar homes nearby sold for.
- If the value is high and the record is right or overstated, file inside your township's window. County forms are free.
- Read every letter from the Board. Answer any notice by its deadline.
Where Censum fits
On Censum's free appeal check you enter a PIN or address and see appeal odds for your home, built from past Board of Review outcomes on similar homes, plus the appeal window that is open. Censum prepares appeal packets if you want help. The Board decides every appeal, and no one can promise a result.
The numbers behind this article
All counts are Censum's tabulation of the Cook County Board of Review Appeal Decision History dataset (Cook County open data, ID 7pny-nedm), queried November 11, 2026, covering tax years 2010 through 2025. They count PIN-level decisions, not complaints. "Raised" means the Board's total assessed value was higher than the Assessor's total value it started from; in the dataset this matches the "Increase" result exactly. "Residential" is the dataset's Residential major class. Houses and townhouses are classes 2-02 to 2-10, 2-34, 2-78 and 2-95. Condo units are class 2-99. Two- to six-unit buildings are classes 2-11 and 2-12. "Owner-filed" is the dataset's Individual/Pro Se filer type. Complaints were grouped by tax year and the dataset's appeal tracking number. Reason counts use the Board's own reason text in the dataset. "Building total went down" compares the sum of Assessor values with the sum of Board values for every PIN in the same complaint.
FAQ
Can the Board of Review raise my assessment if I appeal?
It has the power, but it rarely uses it on homes. From tax year 2010 through 2025 it raised 72 of 2,393,726 house and townhouse decisions.
Will I be warned before an increase?
Yes. State law requires written notice and a chance to be heard before the Board raises an assessment.
Can a school district ask for a higher value on my home?
Yes. Taxing districts and other taxpayers can file complaints that a property is under-assessed, and they must notify the owner. That can happen whether or not you file.
Can I withdraw my appeal?
The Board's published rules don't describe an owner withdrawal step. Call the Board's office before your hearing and ask.
Are condo owners at more risk?
Somewhat. Almost all residential increases were condo units in building-wide complaints, though most of those buildings still came out lower overall.
Does filing on my own make an increase more likely?
Not in the record. Owner-filed house appeals had 20 increases in 757,403 decisions and were lowered 64.3% of the time.
Sources
- Cook County Board of Review, Legal Background
- Cook County Board of Review, Official Rules (2025)
- Cook County Board of Review, Intervenor Valuation Rules
- Cook County Board of Review, Frequently Asked Questions
- Cook County Board of Review, How to Present a Case
- Cook County Assessor, 2026 Official Appeal Rules
- Illinois Property Tax Code, 35 ILCS 200/16-95 (Board powers; changes on its own motion require notice)
- Illinois Property Tax Code, 35 ILCS 200/16-120 (no increase without written notice and a hearing opportunity)
- Censum tabulation of the Cook County Board of Review Appeal Decision History dataset (Cook County open data), tax years 2010 to 2025; PIN-level decisions.
Sources accessed November 11, 2026.
Next step
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Censum LLC is a data and analytics company, not a law firm and not a tax advisor. Censum is independent and is not affiliated with Cook County or any government agency.