For attorney-filed appeals in tax years 2023 through 2025, the Cook County Board of Review's most common reason for granting a reduction was "analysis of comparable properties, a recent sale, and/or an update of property characteristics." It recorded that reason on 190,274 reductions.
Its most common reason for denying one, outside the condominium code, was the same sentence. 194,736 denials.
Same evidence type, same words, a coin flip. What separates the two piles is not whether a comparable grid was submitted. It is whether the grid survived a reading by someone with the same open data the firm has.
Quick Answer
For attorney-filed appeals in tax years 2023 through 2025, the Board's most common grant reason-analysis of comparable properties, a recent sale, and/or an update of property characteristics-appeared on 190,274 reductions. The same sentence led 194,736 denials (outside the condominium code). Another 3,453 denials cited a recent sale of the subject. The grid's search universe and exclusions decide which pile a file joins.
The word the Board put in its rules
Rule 19E of the Board's Official Rules, last updated July 27, 2026, says appraisal reports "shall avoid selective use ('cherrypicking') of data or application of valuation concepts inconsistent with USPAP." The rule is addressed to appraisers. The Board's analysts read paralegal-built grids with the same eyes, and a firm that treats Rule 19E as the standard for every grid loses fewer files to one question: where are the sales you left out?
The sale that sinks the file
One denial code makes the point in miniature. In the same three years, the Board denied 3,453 attorney-filed appeals because "a recent sale of the subject property" supported a higher market value than the assessment. The subject's own sale, in the county's own record, arguing the other side. A grid built from five low neighbors and no look at the subject's deed history is the purest form of selective data, and the Board found it 3,453 times.
Four questions the grid should answer before it is asked
**What was the search?** Neighborhood code, sale-date window, class, size band. "Five sales within half a mile, same class, 2024 and 2025, within 20 percent of the subject's living area" defines a universe. Five addresses do not.
**How many sales were in it?** Twelve returned, five shown, seven excluded with a reason a stranger could check: non-arm's-length transfer, gut rehab, demolition permit within the year.
**Closest fit, or lowest price?** Sort by similarity first. If two of the five most similar sales run above the subject's assessment, put them on the grid and adjust. An honest high comparable is worth more than a hidden one, because the analyst can find the hidden one.
**Is the assessment comparison as disciplined as the sales comparison?** A lack-of-uniformity grid compares assessed values, and the same rule applies. Six lower-assessed neighbors chosen from a block of twenty is selective unless the grid says why those six.
Timing
Rule 19B requires appraisals be dated within the triennial or no more than three years before the January 1 lien date. A paralegal's grid is not an appraisal, but the principle holds: sales as close to the lien date as the market allows, older sales labeled and explained. A prior-triennial sale used because the neighborhood has had no transactions is legitimate when labeled. The same sale dropped silently into a grid of 2025 sales is what the rule calls selective.
Where the counties' books split
Uniformity is the argument attorneys make most. Of attorney-filed residential decisions in 2023 through 2025 that the Board coded by basis, 383,447 rested on comparable-property analysis and 18,809 on cost, income, market data, or an appraisal. The comparable-based files won 49.5 percent of the time. The appraisal-and-market files, 35.6 percent.
Read that as the Board telling firms which evidence it finds easiest to check. A grid is verifiable in minutes against the open data. An appraisal is an opinion.
The header that turns a list into a record
Above the comparable table:
- Search universe: neighborhood code, class, date window, size band.
- Sales returned: N.
- Sales shown: M, sorted by similarity or an explicit adjustment order.
- Sales excluded, one line each, with the reason.
- Lien date, and the date of the most recent sale used.
- Subject's own most recent sale, with date and price, and how it was treated.
Ten minutes of a paralegal's time. It converts addresses into a record the Board can check and, having checked, believe.
The numbers behind this article
Decision counts are Censum's tabulation of the Cook County Board of Review Appeal Decision History dataset (county open data, 7pny-nedm), copy dated May 20, 2026; PIN-level decisions, tax year 2025 incomplete. "Basis" groupings follow the Board's own change and no-change reason codes. Censum is independent and not affiliated with the Board or any county office. Censum's evidence packets carry the search universe and the exclusions alongside the comparables, so the grid a firm submits brings its own audit trail.
Sources
- Cook County Board of Review Official Rules
- Censum tabulation of the Cook County Board of Review Appeal Decision History dataset (Cook County open data, 7pny-nedm), copy dated May 20, 2026; PIN-level decisions; tax year 2025 incomplete in that copy.
- Rules cited: Cook County Board of Review Official Rules 19B and 19E, last updated July 27, 2026.
FAQ
What does Rule 19E say about selective data?
Appraisal reports shall avoid selective use ("cherrypicking") of data or valuation concepts inconsistent with USPAP. Analysts read paralegal-built grids with the same standard.
How often did the subject's own sale sink an attorney-filed appeal?
3,453 denials in tax years 2023 through 2025 because a recent sale of the subject supported a higher market value than the assessment.
How did comparable-based residential files perform versus appraisal-and-market files?
Of attorney-filed residential decisions coded by basis in 2023 through 2025, comparable-property analysis (383,447) won 49.5 percent; cost/income/market/appraisal files (18,809) won 35.6 percent. Those are historical Board measurements, not a promise.
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
Look up the PIN's recent sales and the neighborhood sale universe, then attach a header that states the search, exclusions, and how the subject's own sale was treated. The attorney decides what goes in the complaint.
Censum LLC is independent and not affiliated with Cook County or any government agency.