In the 2020 South and West reassessment, the Board of Review reduced 36,655 residential PINs. At the next reassessment, in 2023, 23,113 of them came back to the Board. For 98.8% of those, the Assessor's new value was above the value the Board had set three years earlier. The median new value was 39.1% higher.
The Board reduced 62.8% of them again. Residential PINs with no Board decision in the prior three years were reduced 49.0% of the time.
Another 9,255 of the 2020 wins had no Board decision in 2021, 2022 or 2023. Nobody refiled them.
The South and West is being reassessed again for 2026. The Board reduced 52,848 residential PINs there in 2023, and attorneys filed 35,972 of them. Those are this year's win-back list.
Quick Answer
A Board reduction on an owner-occupied home generally holds for the rest of its three-year cycle, then the reassessment sets a new value. In the latest cycle in each region, past winners that came back were reduced again more often than first-time PINs: 62.8% vs 49.0% in the South and West in 2023. Thousands of wins are never refiled. Find your own before you prospect.
What the last cycle shows
Residential PINs the Board reduced in one reassessment year, at the region's next reassessment:
- South and West, reduced in 2020: 36,655 PINs. 23,113 (63.1%) came back to the Board in 2023. 98.8% of those had a new value above the one they won, and 62.8% were reduced again, against 49.0% of first-time PINs. 9,255 (25.2%) had no Board decision in the next three years.
- Chicago, reduced in 2021: 69,488 PINs. 53,887 (77.5%) came back in 2024. 81.0% had a new value above the one they won, and 57.6% were reduced again, against 46.6% of first-time PINs. 10,031 (14.4%) had no Board decision in the next three years.
- North suburbs, reduced in 2022: 66,473 PINs. 53,340 (80.2%) came back in 2025. 99.0% had a new value above the one they won, and 66.8% were reduced again, against 53.5% of first-time PINs. 8,210 (12.4%) had no Board decision in the next three years.
"First-time" means a residential PIN with no Board decision in the three tax years before. Attorney-filed files show the same gap: in the South and West in 2023, 60.1% of returning wins were cut again against 42.2% of first-time PINs.
This is a pattern, not a law. In the cycle before, it ran the other way in two regions. South and West wins from 2017 were reduced again 36.0% of the time in 2020, against 44.9% for first-time PINs. Chicago's 2018 wins were reduced again 26.2% in 2021, against 37.8%. Only the North favored past winners both times.
So treat an eroded win as a lead to test, not a case already made. The record says these files deserve a look first. It does not say they will win.
The mechanism
Section 16-147 of the Property Tax Code covers Cook County. When the Board lowers the assessment of a parcel with an owner-occupied residence, the reduced assessment, subject to equalization, stays in effect for the rest of the general assessment period. The exceptions: an interested party shows substantial cause, or the Board's decision is reversed or modified on review.
The reassessment ends that protection. The Assessor revalues the region with a new model and new sales, and the won value is not the starting point. The new number may be fair. It may also repeat the problem your file already proved.
Two kinds of win-back
Eroded wins. The new value sits above the value your firm secured, and the market does not obviously explain the gap.
Wins never refiled. A client won once, then went quiet through the next reassessment. Some sold, and some got relief at the Assessor. The rest are open files nobody reopened.
Why they slip
- Engagement letters are often one-year.
- Clients assume a reduction is permanent.
- The notice goes to the owner, not to you.
- Intake is built around inbound calls, not your own history.
- The Board window is about 30 days, and it opens in a busy season.
How to find them in your book
- List prior wins. Every PIN where your firm secured a Board reduction in the region's last reassessment year, with the won assessed value. For the South and West, that is 2023.
- Pull the new value. Use the 2026 reassessment notice, or the Assessor's certified value once the township closes.
- Flag the gap. Mark parcels where the new value exceeds the won value by a threshold you choose, such as 10%. In 2023, 98.8% of returning South and West wins came back above the won value, so rank on the size of the gap.
- Test the market. Compare the increase with nearby sales of similar homes. A rise that tracks the market is weaker. A rise the market does not support is stronger.
- Check ownership and occupancy. A sale means the new owner is not your client. The carry-forward rule covers owner-occupied homes, so rentals behave differently.
- Rank by value, confidence and window. Recoverable value times modeled confidence, sorted by the township's Board dates.
Re-engaging without a cold pitch
A win-back contact is about the client's own file: "We lowered this assessment in the last cycle. The new reassessment value is higher than the value we won. Here is what we see, and here is the deadline."
Contacting a former client sits differently under the professional conduct rules than contacting someone who has never been a client. Confirm your approach and any required labels with your ethics counsel.
Where Censum Docket fits
Docket's Prospects & win-back lane surfaces eroded and never-re-filed wins in your territory, ready to reactivate. The opportunity queue ranks them by recoverable value and modeled confidence, deadline-boosted for live Board windows, and the protected-client guard keeps current clients out of prospecting.
Censum is not a legal referral service and never takes a share of legal fees. Your firm keeps the client, the judgment and the filing.
The numbers behind this article
Censum's tabulation of the Board's decision history, tax years 2017 through 2025, accessed November 7, 2026, at the PIN level. "Residential" is the dataset's major class. "Reduced" means a decision of Decrease. "New value above the won value" compares the Assessor value on the later Board decision with the Board's value from the earlier one, for PINs that came back. A PIN that was divided or renumbered drops out of the match, so "never came back" also counts some sold, split or renumbered parcels. South and West, Chicago and North are the county's three reassessment regions.
Sources
- Censum tabulation of the Cook County Board of Review Appeal Decision History dataset (Cook County open data), accessed November 7, 2026; PIN-level decisions.
- Illinois Property Tax Code, 35 ILCS 200/16-147, reduced assessment of homestead property.
- Cook County Assessor, Assessment and Appeal Calendar.
- Cook County Board of Review, Dates and Deadlines.
FAQ
Does a Board of Review reduction carry forward?
For an owner-occupied residence, generally yes, through the rest of the three-year cycle, under 35 ILCS 200/16-147. It does not carry past the next reassessment.
Do past wins win again?
In the latest cycle in each region they did more often than first-time PINs: 62.8% vs 49.0% in the South and West (2023), 57.6% vs 46.6% in Chicago (2024), 66.8% vs 53.5% in the North (2025). In the cycle before, two regions showed the opposite. History is not a forecast.
Is an eroded win automatically a good case?
No. Prices may have risen. The gap is a signal to test, not a conclusion.
What about commercial wins?
The owner-occupied carry-forward rule does not apply. Commercial values are often revisited sooner, so check them every year.
Should we contact owners who sold?
The new owner was never your client. Treat that as new-client outreach under the solicitation rules.
Does Censum file or represent clients?
No. Censum LLC is independent property-tax intelligence and docket tooling. It is not a law firm. The attorney files and makes every legal judgment.
Next step
Start with the wins you already have: every South and West PIN your firm won in 2023, against its 2026 value. See Docket's win-back lane
Censum LLC is independent and not affiliated with Cook County or any government agency.