The Illinois Property Tax Appeal Board treats a requested change of $100,000 or more in assessed value differently: taxing districts get notice, a court reporter is provided, and the school district can show up with its own appraiser. At $300,000 or more, judicial review of PTAB's decision goes straight to the appellate court.
Here is how often Cook County files actually reach those lines, from the Board of Review's own decision history for tax years 2023 through 2025:
- **Residential:** 425,806 reductions granted; 305 at $100,000+ AV; 44 at $300,000+ AV; median reduction $2,081.
- **Multifamily:** 10,594 reductions granted; 2,035 at $100,000+ AV; 713 at $300,000+ AV; median reduction $25,218.
- **Commercial and industrial:** 48,029 reductions granted; 9,250 at $100,000+ AV; 4,362 at $300,000+ AV; median reduction $17,408.
Residential files cross the $100,000 line seven times in ten thousand. Commercial files cross it one time in five. The PTAB intervention problem is a commercial and multifamily problem, and a firm's PTAB triage should start from that fact.
Quick Answer
For tax years 2023 through 2025, residential Board reductions numbered 425,806; only 305 crossed PTAB's $100,000 assessed-value line (44 crossed $300,000). Commercial and industrial crossed $100,000 in 9,250 reductions. PTAB petitions must be filed within 30 days of the Board's written decision; the Board's three-day re-review does not pause that clock. Triage commercial and multifamily first.
The clock
PTAB's guidance: a petition "must be filed within 30 days of the board of county review's written decision," and "your appeal will be rejected if you fail to file on time." Thirty days from the postmark of the Board's decision or from personal service. Mailed petitions and evidence count as filed on the postmark date.
The first act on a decision letter is recording the postmark, not the scan date. In a firm that batches mail, those can differ by a week.
The Board's three-day re-review window (Rule 26) runs at the same time. Asking the Board to look again does not pause PTAB's clock. If re-review comes back on day 28, two days remain.
What the Board says about pending PTAB matters
One decision code in the Board's history matters for anyone running both lanes. For attorney-filed appeals, 2023 through 2025, the Board issued 10,273 no-change decisions with this reason: "This parcel is currently the subject of a matter pending before PTAB for a prior year or the Assessor held prior Board of Review action."
A prior-year PTAB petition still open can hold the current-year Board appeal in place. A firm that files PTAB on a marginal file has, in effect, spent next year's Board appeal on that parcel too. That belongs in the triage math.
What goes in
For assessment years 2016 and after, PTAB wants one copy each of the petition form, the Board's final decision (or a favorable prior PTAB decision on the property), and all evidence. Over 500 pages, three collated sets. PTAB is a new proceeding; the Board's evidence does not travel automatically.
The appraisal question, in dollars
PTAB does not require an appraisal. It calls one the best evidence, expects it to examine "the three traditional approaches to value," and warns that when the appraiser does not testify, the absence "may diminish the weight afforded to the appraisal." An appraisal plus a testifying appraiser is a real fee against the amount in dispute after the Board's decision.
Convert before deciding. Residential property in Cook County is assessed at 10 percent of market value, commercial at 25 percent. A $100,000 assessed-value dispute is a $1 million market-value dispute on a house and a $400,000 one on a store.
A four-lane sort a paralegal can run on decision day
- **Accept.** The Board granted most of the request. Calendar next cycle.
- **Re-review only.** The Board missed something already in the record. Three days from the letter date. No new evidence.
- **PTAB, documentary.** Declined, meaningful dollars, strong on paper (uniformity grid, arm's-length sale, characteristic error the Assessor's record confirms). File within 30 days of postmark. Budget for the packet, not an appraiser.
- **PTAB, appraisal.** Large dollars, evidence needs a signature, likely to cross $100,000 in assessed value. Engage the appraiser before filing. Tell the client the taxing districts may intervene, and that next year's Board appeal on this parcel may be held.
Files not sorted by day ten go to the attorney by name with the postmark in the subject line.
The circuit-court lane
Illinois also allows paying under protest and filing a tax objection in the circuit court. It is a separate proceeding with its own rules and timing, it does not rescue a missed PTAB deadline, and choosing between the two is an attorney's forum judgment. This article does not summarize the objection rules; verify current statute before advising a client on that path.
The numbers behind this article
Reduction counts and thresholds 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 classification descriptions. Censum is independent and not affiliated with PTAB, the Board, or any county office. Censum's docket records the postmark and runs the three-day and thirty-day clocks side by side; whether to petition, and on what theory, is the attorney's call.
Sources
- Illinois Property Tax Appeal Board - Getting Started
- 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.
- Sources: Illinois Property Tax Appeal Board, "Getting Started" and "Practice and Procedures"; Cook County Board of Review Official Rules, Rule 26, last updated July 27, 2026.
FAQ
When does the PTAB thirty-day clock start?
From the postmark of the Board's decision or personal service. Mailed petitions and evidence count as filed on the postmark date. Record the postmark, not only the scan date.
Does Board re-review pause PTAB?
No. Rule 26's three-day re-review runs at the same time. If re-review returns on day 28, two days remain for PTAB.
How often did the Board hold files for pending PTAB?
For attorney-filed appeals in 2023 through 2025, 10,273 no-change decisions cited a matter pending before PTAB for a prior year or Assessor-held prior Board action.
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 each newly issued Board decision in the firm docket: capture the postmark, run the three-day and thirty-day clocks side by side, and have the attorney choose the lane. Censum does not petition PTAB.
Censum LLC is independent and not affiliated with Cook County or any government agency.