Attorneys filed at the Cook County Board of Review on 278,145 PINs in both tax year 2024 and tax year 2025. On 17,887 of them, 6.4%, the 2025 filing came from a different firm.
Over a full reassessment cycle the number is larger. Of the PINs attorney-filed in both 2021 and 2024, Chicago's last two reassessment years, 23.5% changed firms.
Clients rarely call to say they hired someone else. They stop answering, and the next time you look, another firm's code is on their parcel. The Board's record shows where, if you match it against your book.
Quick Answer
The Board's published decisions carry the filing attorney's code on every PIN, every year. Of PINs attorney-filed in both 2024 and 2025, 6.4% changed firms; across the 2021 to 2024 cycle, 23.5% did. Match the record to your client PINs once a year and you will see which clients a competitor filed on, where, and with what result. During the cycle, Board Rule 10 decides whose complaint counts: the first one filed.
How often clients move
PINs with an attorney filing in both years, and how many had no firm in common:
- 2021 to 2022: 253,642 PINs attorney-filed both years; 26,741 (10.5%) changed attorney code; 16,549 (6.5%) changed firm.
- 2022 to 2023: 244,461 PINs; 17,975 (7.4%) changed code; 14,526 (5.9%) changed firm.
- 2023 to 2024: 246,803 PINs; 26,318 (10.7%) changed code; 24,207 (9.8%) changed firm.
- 2024 to 2025: 278,145 PINs; 26,427 (9.5%) changed code; 17,887 (6.4%) changed firm.
- 2021 to 2024, one full cycle: 359,899 PINs; 97,302 (27.0%) changed code; 84,434 (23.5%) changed firm.
- 2022 to 2025, one full cycle: 299,274 PINs; 62,028 (20.7%) changed code; 54,933 (18.4%) changed firm.
Two readings matter. First, the code changes more often than the firm, because firms move files among their own attorneys. Watch the firm, not just the code. Second, the highest one-year rate, 9.8%, came in 2024, Chicago's reassessment year. Over a whole cycle, roughly one repeat PIN in five changed firms.
Some clients leave counsel altogether. 3,332 PINs filed by an attorney in 2024 were filed only pro se in 2025.
What the record shows, and when
After the fact: the decision record. Each decision carries the attorney code. Matched to your PIN list, it shows every client parcel where another firm filed, by township, class and result. Decisions post over months, so this signal lags the cycle.
One decision per PIN. In 2023, 2024 and 2025 the Board's published data has exactly one decision for each PIN each year. A second, competing complaint does not appear as a second decision.
During the cycle: Rule 10. The Board's Rule 10 says a taxpayer's initial complaint controls and later complaints for the same PIN are void. A taxpayer's own complaint overrides an attorney filing, and a later pro se filing controls. Attorneys substituting their appearance file the Board's Substitution of Representation form, and an email timestamp decides the attorney of record.
If another firm filed first, your complaint is the one that does not count. The in-cycle signal is the client conversation, before you file.
Why clients move
- A competitor reached them first in a reassessment year.
- Price: a lower percentage, or a flat fee.
- A neighbor, relative or condo board recommended someone else.
- Your firm did not contact them when the notice arrived.
- A result disappointed them and nobody explained why.
The record cannot tell you which reason applies. It tells you where to look.
How to run the match
- Clean your book to PINs. Fourteen digits, with condo units, parking and storage PINs listed separately.
- List your codes. Every attorney at the firm, plus predecessor firms.
- Pull decisions for your townships. At least the last three complete tax years. 2025 appeared complete in November 2026.
- Flag any client PIN with another firm's code. Note the township, class, year and result.
- Group the flags. One competitor sweeping a township shows up as a cluster. So does a condo building moving as a block.
- Separate the explainable cases. See below.
Read the flags carefully
Not every flag is a lost client:
- Sold properties. The parcel's new owner is not your client.
- Association filings. A condo association's attorney may file for every unit, including units whose owners are in your book.
- Attorneys who moved. A lawyer who changes firms takes a code with them. Firm names also vary in spelling from year to year.
- Multi-PIN properties. One engagement can generate many PIN-level decisions.
- Incomplete years. Check that the newest year has finished posting before you count.
Responding well
- Contact the client about their file, not the competitor. Ask what changed. Disparaging another firm rarely wins anyone back.
- Do not file a second complaint. Under Rule 10 a later complaint on the same PIN is void, and the client's own filing overrides yours.
- Fix the gap that caused it. Often that is reassessment-year outreach that started too late.
- Watch the next cycle. Clusters predict where a competitor will push next.
Where Censum Docket fits
Docket's win intelligence flags when a competitor files on one of your clients, and its territory map shows at-risk clients and your gap to the leader across all 38 townships. Matching runs on your uploaded book, 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.
The numbers behind this article
Censum's tabulation of the Board's decision history, tax years 2021 through 2025, accessed November 7, 2026, at the PIN level. A PIN "changed firms" when none of the firms on its attorney filings in the first year appears on its attorney filings in the second. Firm names were standardized for case, punctuation and suffixes such as LLC; an attorney code with no firm name counts as its own firm. Spelling changes, mergers and attorneys moving between firms can still register as a change. "Different attorney code" is the same test on codes alone.
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.
- Cook County Board of Review Official Rules, Rules 2 and 10, last updated July 27, 2026.
- Censum, 100,458 attorney-filed appeals died on paperwork.
FAQ
Is this monitoring my clients?
It is reading public decisions about parcels in your book. It does not involve contacting anyone or accessing anything private.
What happens if two firms file on the same PIN?
Under Rule 10 the initial complaint controls and later complaints for that PIN are void. A taxpayer's own complaint overrides an attorney filing. Resolve it with the client quickly.
Can I see competitor filings before decisions post?
Not from the published record, which shows one decision per PIN after the fact. The earliest signal is your own client contact before you file.
Should I contact a client who moved?
A current or former client relationship sits differently under the conduct rules than a stranger. Confirm your approach with your ethics counsel.
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
Run your client PINs against the 2025 decisions and list every parcel with another firm's code. See Docket's book-activity flags
Censum LLC is independent and not affiliated with Cook County or any government agency.