Property tax appeals got much harder to win between 2021 and 2025
The Cook County success rate roughly halved in four years, from 31.9% to 16.2%, while the number of appeals stayed high. What the data shows, and what it does not explain.
If your neighbour tells you they won an appeal a few years ago and it was straightforward, they are not exaggerating. They were operating in a materially different environment.
The trend
| Tax year | Decided | Reductions | Success rate |
|---|---|---|---|
| 2021 | 373,626 | 119,354 | 31.9% |
| 2022 | 302,306 | 74,953 | 24.8% |
| 2023 | 243,415 | 52,169 | 21.4% |
| 2024 | 440,010 | 93,373 | 21.2% |
| 2025 | 362,508 | 58,886 | 16.2% |
| 2026 (partial) | 66,790 | 12,623 | 18.9% |
The success rate roughly halved. Appeal volume did not fall with it — 2024 saw the highest number of decided appeals in the series, at 440,010.
More people are appealing. Fewer are winning.
What might explain it
We can set out plausible causes. The data does not choose between them, and presenting a tidy story we cannot support would be worse than saying so.
Assessments catching up to the market
The most likely single contributor. House prices rose sharply from 2020, and assessment rolls lag the market by design — values are set as at 1 January and rebuilt on a three-year cycle.
In 2021, many assessments still reflected pre-surge values. As reassessments worked through, values moved closer to what properties were actually worth — and the gap an appeal could exploit narrowed.
On that reading the fall is not offices becoming stricter. It is there being less error to find.
Volume
440,010 decided appeals in one year is an enormous workload compressed into the months after each township's roll publishes. Whether that affects how marginal cases are treated is a fair question, and this data cannot answer it.
The composition of who files
If a rising share of filings are speculative — sent because a firm mailed everyone whose assessment rose, rather than because a specific disparity was identified — the success rate falls without anything changing about how appeals are judged.
2021 as the outlier
It is worth considering the trend from the other end. 2021 had both the highest success rate and the largest gap between agent-filed and owner-filed appeals (33.0% against 25.0%). It may simply have been an unusual year, with values set in unusual conditions, rather than a normal baseline from which things declined.
What it means for you
Discount second-hand experience. Advice from someone who appealed successfully in 2021 is advice from a different environment — roughly twice as favourable.
The base rate matters more now. At 31.9% a speculative filing was a reasonable gamble. At 16.2% it is not, and the case for checking the arithmetic before spending the evening is stronger.
The strong arguments are unaffected. The fall is in the overall rate, which pools every filing including the hopeful ones. A demonstrable record error — the county's file says 2,400 square feet and your survey says 1,900 — is not a matter of market conditions, and neither is a tight uniformity case against four near-identical neighbours.
Exemptions are unaffected entirely. They are statutory entitlements, not contested arguments. A Cook homestead exemption is worth around $750 a year regardless of what appeal success rates are doing, and it is granted on an application.
The caveats
This is the Assessor only; the Board of Review keeps its own record. 2026 is partial and its 18.9% may move as the season completes. And rates vary four-fold by township within any single year, so the county-wide figure is an average of very different places.
Everything here is counted from the Cook County Assessor's published appeal decisions, dataset
y282-6ig3, which anyone can download and check.