In tax year 2021, the Cook County Board of Review cut the assessed value of 69,488 residential properties in Chicago. Three years later, at the city's next reassessment, 43,626 of them came back to the Board with a new Assessor value above the one they had won.
The win was real. It had an end date. If you won a reduction, the next reassessment notice is the one to read closely.
Quick Answer
In Cook County, a Board of Review reduction on an owner-occupied home generally stays in effect for the rest of that three-year assessment cycle. At the next reassessment, the Assessor sets a fresh value, and the old reduction does not carry forward. Of 53,887 Chicago homes cut in 2021 that came back to the Board in 2024, 81.0% started above the value they had won. When your new notice arrives, compare it with your old value before the window closes.
How long a win lasts
Illinois law says that in Cook County, when the Board of Review lowers the assessment on a parcel with a residence occupied by its owner, the reduced value remains in effect for the rest of the general assessment period. The exceptions are a showing of substantial cause, or the Board's decision being reversed or modified on review.
Cook County reassesses one region every three years:
- South and west suburbs: 2026
- City of Chicago: next on the rotation, in 2027
- North suburbs: 2025, then 2028
So a reduction won in your reassessment year can carry through the next two tax years. A reduction won in the second or third year of the cycle helps for fewer years.
Two caveats. The rule is about owner-occupied homes. If the property is a rental, check each year instead of assuming the reduction held. And your bill can still rise during the cycle, because tax rates and the state multiplier change every year. Our guide to why a bill can rise after a lower assessment walks through that.
What happened to Chicago's 2021 winners
Chicago was reassessed in 2021 and again in 2024. That makes the city a clean test: take every residential property the Board cut in 2021 and look at what the Board saw in 2024.
Chicago residential properties:
- Cut by the Board in tax year 2021: 69,488.
- Back at the Board in tax year 2024: 53,887, or 77.5% of the 2021 group.
- Started 2024 above the 2021 Board value: 43,626, or 81.0% of those back.
- Cut again by the Board in 2024: 31,023, or 57.6% of those back.
- Still above the 2021 Board value after the 2024 decision: 39,751, or 73.8% of those back.
The typical jump was large. Among the 53,887 that came back, the median 2024 Assessor value was 12.5% above the value the Board had set in 2021. For houses and other non-condo property, the median was 21.1%, and 89.7% started higher. For condominium units, the median was 4.2%, and 69.4% started higher.
Three cautions:
- Some of the rise may be real. Prices can climb over three years. A higher number is not proof of an error.
- The record does not say who lived there. These counts include rentals as well as owner-occupied homes.
- 15,601 of the 2021 winners did not come back to the Board in 2024. The dataset has no 2024 value for them, so they are not in the shares above.
The second result matters as much as the first. The 2021 winners that came back were cut again 57.6% of the time. Other Chicago residential decisions in 2024 were cut 38.6% of the time. That is history, not a forecast for your home, but it says a past win is worth checking again.
What to do with this: if you are in Chicago, the 2027 notice is the one to watch. If you are in the south and west suburbs, your 2026 notice was that notice; check the Assessor's and the Board's calendars for any window still open in your township.
What happens at the reassessment
In a reassessment year the Assessor revalues every property in the region using recent sales and a new valuation model. Your home gets a new estimated market value, and the notice mails with a short appeal window.
The new value is not built on top of your win. If the model lands above the value the Board set last time, the reduction is gone unless you appeal again. That is what people mean when they say a win "crept back."
Sometimes the higher number is fair. Sometimes it repeats the problem you proved last time.
The three-number check
When your new notice arrives, put three numbers side by side.
1. The value you won. It is on your Board of Review decision. If you no longer have the letter, the assessed value on the bills after the win shows it.
2. The new value. It is on your reassessment notice. For a home, assessed value is 10% of the estimated market value, so multiply assessed value by 10 to compare market values.
3. What the market did. Look at sales of similar homes near you since your win. If they rose by roughly as much as your value did, the new number may be fair. If they did not, that gap is a signal worth checking.
Why winners skip the next round
The record cannot say why 15,601 of Chicago's 2021 winners did not return to the Board in 2024. Some may have appealed only at the Assessor, sold, or seen a fair value. But people who won before often skip the next round for predictable reasons:
- They assume the reduction is permanent.
- Their help was a one-year engagement, so nobody reminded them.
- The notice lands in a busy season and the window is a few weeks.
- They think a second appeal looks greedy. It does not. Each year's value stands on its own evidence.
What your old win tells you
Your past win is useful, with limits.
What carries over: if you won because the county had a fact wrong, such as square footage, bedroom count, or a finished basement you do not have, check the new property record card. If the error is back, that is strong evidence. Our guide to property record card errors shows where to look.
What does not: the comparable sales that won last time may be three years old now. The Board looks at current evidence, so refresh the comparisons.
Keep the decision letter, your old packet, photos and closing papers in one folder. They make the next file faster.
The numbers behind this article
The Chicago figures are Censum's tabulation of the Cook County Board of Review Appeal Decision History dataset, accessed November 7, 2026. They cover residential PINs in the city's eight assessment townships. "Cut in 2021" means a Board decision of Decrease for tax year 2021. "Back at the Board" means the same PIN has a tax year 2024 decision. The 2024 starting value is the Assessor's value shown in that 2024 record. Figures count PIN-level decisions, not appeals filed. PINs that were split or renumbered between 2021 and 2024 would not match and are not counted. Censum is independent and not affiliated with the Board or any county office.
Sources
- Illinois Property Tax Code, 35 ILCS 200/16-147 (reduced assessment of homestead property)
- Cook County Assessor, assessment calendar and deadlines
- Cook County Assessor, report noting Board values on owner-occupied homes remain for the triennial
- Cook County Board of Review, residential appeals
- Censum tabulation of the Cook County Board of Review Appeal Decision History dataset (Cook County open data), accessed November 7, 2026; PIN-level decisions.
FAQ
Does my Board of Review reduction carry over to next year?
For an owner-occupied home, it generally carries through the rest of that three-year cycle, unless substantial cause is shown or the decision changes on review. It does not survive the next reassessment.
Did Chicago's 2021 winners keep their lower values?
Not at the next reassessment. Of 53,887 Chicago residential properties cut in 2021 that came back to the Board in 2024, 43,626 (81.0%) started 2024 above the value they had won. After the Board's 2024 decisions, 73.8% were still above it.
Do I have to appeal every year?
Not necessarily. Within a cycle, a reduction on an owner-occupied home generally holds. In your next reassessment year, plan to check the new value. Rental owners should check every year.
Does winning once make it easier next time?
Prior appeal outcomes are one of the signals Censum weighs, and an accurate record helps. Chicago's 2021 winners that returned in 2024 were cut again 57.6% of the time. But each appeal is decided on that year's evidence. A past win is not a guarantee.
What if I sold the home?
The reduction belongs to the property's assessment, not to you. The new owner benefits from it until the next reassessment, and any future appeal is theirs to file.
Next step
When your reassessment notice arrives, run the free check again and compare the new value with the one you won. Check my property again
Censum LLC is a data and analytics company, not a law firm and not a tax advisor. You file your own appeal. Censum is independent and is not affiliated with Cook County or any government agency.