Between tax years 2023 and 2025 the Cook County Board of Review issued 149,824 PIN-level decisions on commercial and industrial appeals. Attorneys filed 99.6 percent of them. The Board reduced the assessment in 48,029, a rate of 32 percent.
Among the reductions, the median cut was $17,408 in assessed value. The top quarter of winning files cut $65,976 or more, and 9,250 files cut $100,000 or more. At the 25 percent level of assessment that applies to commercial property in Cook County, a $100,000 assessed-value reduction is a $400,000 change in the county's opinion of market value.
So the commercial lane is where the money is, and it is also where two out of three files come back unchanged. The Board's Official Rules, last updated July 27, 2026, list the documents it expects for income property. Here is the list, in the order the Board reads it, with the paralegal's job for each item.
Quick Answer
Between tax years 2023 and 2025 the Board issued 149,824 commercial and industrial PIN-level decisions; attorneys filed 99.6 percent. It reduced 48,029 (32 percent). Among winners, 9,250 cut $100,000 or more in assessed value. Two of three files still come back unchanged-Rules 14B, 20, and 21 name the documents the Board expects for income property.
1. The Historical Summary Form
Rule 14B: "All parties shall submit a complete Historical Summary Form for all income producing properties other than class 2 residential subjects."
Every income parcel outside residential class 2. Office, retail, industrial, larger multifamily, and the less obvious ones: a mixed-use building with ground-floor retail, a paid parking lot, self-storage. "Complete" is the operative word. Revenue filled in and expenses blank reads as a more profitable property than the owner has.
Paralegal task: pull three years of operating statements before the township opens and reconcile them to the form line by line. Where the client's bookkeeping categories do not match the form, write the mapping down.
2. Three years of Schedule E, or the affidavit route
Rule 20: "the taxpayer or his/her attorney shall file with the Board a copy of Schedule E of the taxpayer's 1040 IRS form for the three years prior to the lien date."
For a 2026 complaint, that is 2023, 2024, and 2025. The 2025 return may not be filed when the township opens. The rule's structure allows an affidavit with income and expense statements instead, and the affidavit works, but the Board reads it as a substitute. Note in the file why Schedule E was not produced.
Entity-held property has no personal Schedule E. The equivalent is the entity return and its rental schedules. Accountants do not move on a thirty-day window, so this request goes out in the spring.
3. Rent rolls with totals, and leases the Board can check
Rule 20 says the Board "will consider lease summaries, audited financial statements, rent rolls with totals and representative samples of leases."
A rent roll that does not total, or totals to a figure that disagrees with the Historical Summary Form, will be noticed. The lease sample should include the largest tenant, any tenant with unusual terms (free rent, percentage rent, below-market renewal), and any tenant in default. The sample exists so the Board can confirm the rent roll reflects contract rent.
Paralegal task: a one-page reconciliation tying rent-roll totals to the form's gross income line, with a footnote for every variance. It saves the attorney the first five minutes of any hearing.
4. The vacancy affidavit
Vacancy is the argument the Board hears most and believes least without paper. Rule 21 lists the paper: a Vacancy-Occupancy Affidavit, dated photographs of the interior vacant space, and an affidavit "setting forth the duration of and the reason for vacancy, and the attempts made to lease the vacant space."
The third element is where files fail. "Attempts made to lease" means listing agreements, dated marketing materials, a showing log, correspondence with prospects. "Actively marketed" is a conclusion. If the vacancy has a public cause (a tenant bankruptcy, a fire, a code order), include the record.
5. The appraisal, if there is one
The Board does not require one. Where a firm submits one, Rule 19B requires it be dated within the triennial period or no more than three years before the January 1 lien date, and Rule 19E requires that reports "avoid selective use ('cherrypicking') of data or application of valuation concepts inconsistent with USPAP." Ask the appraiser before engagement how the report will show the comparables it rejected.
One more number from the Board's decision codes: for attorney-filed appeals in 2023 through 2025, the Board recorded 37,717 no-change decisions under "consideration given to cost, income, or market data and/or your appraisal." The Board read the income package and disagreed with it. That is a different failure from the 57,961 attorney-filed files where no documentation was submitted beyond the complaint form, and it needs a different fix: better inputs, not more of them.
6. Multi-PIN campuses
Rule 9 requires all related PINs on one complaint. For a center with outlots, a tower with a parking structure under its own number, or an industrial site where building and yard were platted separately, the income has to be allocated across PINs in a way the Board can follow. Choose the method before drafting and apply it in the Historical Summary Form.
Where the commercial book lives in 2026
Commercial and industrial decisions, tax years 2023 through 2025, South and West townships in this year's reassessment:
- **Proviso:** 6,391 commercial/industrial decisions; 2,028 reductions; 214 reductions of $100,000+ AV.
- **Thornton:** 6,124 commercial/industrial decisions; 2,440 reductions; 201 reductions of $100,000+ AV.
- **Worth:** 5,973 commercial/industrial decisions; 1,855 reductions; 258 reductions of $100,000+ AV.
- **Lyons:** 5,267 commercial/industrial decisions; 1,585 reductions; 228 reductions of $100,000+ AV.
- **Bremen:** 3,844 commercial/industrial decisions; 1,154 reductions; 95 reductions of $100,000+ AV.
- **Cicero:** 2,320 commercial/industrial decisions; 660 reductions; 90 reductions of $100,000+ AV.
- **Bloom:** 2,295 commercial/industrial decisions; 989 reductions; 105 reductions of $100,000+ AV.
- **Stickney:** 2,067 commercial/industrial decisions; 655 reductions; 195 reductions of $100,000+ AV.
Stickney is the smallest book in that table and produces nearly as many six-figure reductions as Lyons. Industrial corridors do that.
The packet, in reading order
- Historical Summary Form, complete.
- Reconciliation page: rent roll to gross income, variances footnoted.
- Rent roll with totals.
- Representative leases.
- Schedule E for three prior years, entity equivalent, or affidavit with statements.
- Vacancy-Occupancy Affidavit, dated interior photographs, leasing-effort file.
- Appraisal, if any, inside the Rule 19B window.
- Public records for any vacancy cause.
The numbers behind this article
Decision counts and reduction figures 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; counts are PIN-level decisions and tax year 2025 is incomplete. Levels of assessment are from the Assessor's published classification descriptions. Censum is independent and not affiliated with any county office. In Censum's commercial packets, income, expense, and cap-rate inputs are labeled by source, owner-provided or market reference, so the attorney knows which numbers the Board will be asked to trust.
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 9, 14B, 19B, 19E, 20, 21, last updated July 27, 2026.
FAQ
What is the Historical Summary Form requirement?
Rule 14B: all parties shall submit a complete Historical Summary Form for all income-producing properties other than class 2 residential subjects.
Which tax years of Schedule E does Rule 20 want for a 2026 complaint?
The three years prior to the lien date: 2023, 2024, and 2025. An affidavit with income and expense statements is the substitute route when Schedule E is not available; entity-held property uses the entity return and rental schedules.
How many attorney-filed files lost for no documentation beyond the complaint form?
57,961 in tax years 2023 through 2025-a different failure from the 37,717 no-change decisions coded to consideration of cost, income, market data, and/or appraisal.
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
For each commercial PIN still open this cycle, look up the parcel and assemble the packet in reading order: complete Historical Summary Form, rent-roll reconciliation, leases, Schedule E or affidavit, and vacancy file if claimed. The attorney decides what to file.
Censum LLC is independent and not affiliated with Cook County or any government agency.