In tax year 2025 the Cook County Board of Review decided 523,042 PINs on 288,750 appeal numbers. Nearly half of those PIN decisions, 49.4%, came on appeals that covered more than one PIN. 496 appeals covered 100 or more PINs each, and the largest covered 989.
Those are mostly condominium buildings. Of the 496, 464 were mostly condo units, and 95.3% of their 129,388 PINs were condo units: one client relationship, one street address, hundreds of parcels. A prospect list built from names or addresses will miss most of them.
The book also moves. 17,887 PINs that attorneys filed in both 2024 and 2025 changed firms between the two years.
The fastest way to damage a client relationship in a reassessment year is to send that client a letter offering to become their attorney. Good prospecting starts with a list of who not to contact, keyed on PIN and rebuilt before every campaign.
Quick Answer
Before any prospect list, mailing or opportunity queue runs, load current clients, association units, partner-protected parcels, open matters and opted-out owners into a suppression list. Leave former clients off it: they are your best win-back leads, not people to avoid. Match on PIN, not name or address: in 2025, nearly half of all Board decisions came on multi-PIN appeals. Make it fail closed, so nothing goes out if the list does not load. Refresh it before every campaign, because 6.4% of repeat attorney-filed PINs changed firms in a single year.
The numbers that shape the list
Board decisions by appeal number, tax years 2024 and 2025:
| 2024 | 2025 | |
|---|---|---|
| PIN decisions | 571,841 | 523,042 |
| Appeal numbers | 272,195 | 288,750 |
| Appeals covering more than one PIN | 26,666 | 23,965 |
| Appeals covering 100 or more PINs | 594 | 496 |
| Share of PIN decisions on multi-PIN appeals | 57.1% | 49.4% |
And PINs attorney-filed in two years running:
| Years compared | PINs attorney-filed both years | Changed firms |
|---|---|---|
| 2024 to 2025 | 278,145 | 17,887 (6.4%) |
| 2021 to 2024 (one cycle) | 359,899 | 84,434 (23.5%) |
So what. One association file can put hundreds of PINs on your protected list. And a list built last season is already out of date: about one repeat PIN in sixteen changed firms in a year, and nearly one in four over a cycle.
What goes wrong without it
- Your own clients get a "new client" offer. It reads as if you forgot them.
- A condo association you represent sees its unit owners solicited. That puts the association relationship at risk.
- A referral partner's clients are targeted. Now you have a partner problem as well.
- Someone who asked not to be contacted is contacted again. That is a complaint waiting to happen.
- A parcel with an open matter gets prospected. Under Board Rule 10, the first complaint on a PIN controls and later complaints are void. A second complaint on a represented PIN is wasted work, and confusing for the owner.
What belongs on the list
- Every PIN your firm currently represents
- Every unit PIN in buildings where you represent the association
- Related PINs: condo parking and storage, and multi-PIN commercial campuses (Rule 9 puts them on one complaint)
- Parcels protected under referral or partner agreements
- Owners who opted out, by PIN and by mailing address
- PINs with open matters at any venue
Don't block more than you must
Every PIN on the list is an owner you will not contact. Keep it to the people you must not prospect, and nothing more.
Former clients do not belong on it. A client whose matter closed, who skipped a year, or whose old reduction has worn off already knows your firm, and you already know the property. Those are the warmest leads in your territory. Put them on a separate win-back list and contact them as former clients, not as strangers. See how to win back eroded wins.
Suppress a former client only when there is a reason to: they asked not to be contacted, or they have hired another firm for the parcel.
Match on PIN, not on names
Names and addresses fail in predictable ways. A condo building has one street address and hundreds of PINs. Owners change names, title is held in trusts and LLCs, and mailing addresses differ from property addresses.
The 14-digit PIN is the stable key. Match on it first. Use owner name and mailing address as a second check, not the primary one.
Make it fail closed
If the suppression list fails to load, is out of date, or is empty when it should not be, nothing should run. That rule is the whole point. A list that fails open will eventually send the one letter you most wanted to stop.
Practical controls:
- Refresh the suppression list before every campaign, not once a season.
- Record the list's version and date with each campaign.
- Block any campaign whose list is older than a set number of days.
- Check the count. A list for a firm with a few hundred association units should never load with a few dozen PINs.
Campaign controls after suppression
Suppression is the first gate. A clean campaign also needs:
- A frozen cohort. Lock the exact PINs approved, so the list cannot drift after approval.
- A record of what was sent. The creative, the claims in it and the landing page version.
- Delivery and rejection logs. Addresses rejected, duplicates removed, pieces returned.
- Honest measurement. A scan is not a lead. A signed engagement is not a won appeal. Count each stage separately.
The professional rules still apply
A clean list does not make a mailing compliant on its own. Written outreach to prospective clients must follow the Illinois rules on lawyer advertising and solicitation. Confirm current labeling and content requirements with your ethics counsel.
Where Censum Docket fits
Docket's protected-client guard lets you upload your book so your clients are kept out of other firms' prospect lists, and the opportunity queue applies the same check. Matching runs on the 14-digit PIN; a row that is not a valid PIN is rejected, not guessed at from an address. The guard fails closed: when a check has not run or a relationship is unclear, the row is held back instead of shown.
Your own book is not thrown away. Docket re-screens the parcels you upload for a fresh case and shows them to your firm only, and the queue has lanes for your past files that got no change and for past wins whose assessments have climbed back.
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, accessed November 7, 2026, at the PIN level. An "appeal number" is the tracking number in the Board's appeal ID; PINs sharing one number were decided under one appeal. A PIN "changed firms" when none of the firms on its attorney filings in the first year appears in the second, after standardizing firm names; spelling changes and attorneys moving between firms can still count as a change.
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 9 and 10, last updated July 27, 2026.
- Illinois Rules of Professional Conduct of 2010, Rules 7.1 to 7.6.
FAQ
How often should we refresh the list?
Before every campaign, and whenever engagements open or close. In a reassessment year that can mean weekly. Between 2024 and 2025, 6.4% of repeat attorney-filed PINs changed firms.
What about clients who sold their property?
Remove the sold PIN from protection once the relationship ends for that parcel. If the client bought another Cook County property, add that PIN.
Should opt-outs be by PIN or by person?
Both. An owner with several properties who opts out once expects never to hear from you about any of them.
Does suppression replace a conflict check?
No. It prevents unwanted outreach. Conflict checks for engagements remain a separate step.
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
Rebuild the list from current PINs, every association unit included, before the next mailing. See Docket's protected-client guard
Censum LLC is independent and not affiliated with Cook County or any government agency.