Commercial real estate carries a tax disadvantage built into the assessment itself — and most owners discover it only when the bill lands. In Cook County, commercial and industrial property is assessed at a higher percentage of market value than homes are, which means the same dollar of over-assessment hits a commercial owner roughly two and a half times harder. That math is the whole reason a commercial appeal is worth getting right, and worth getting right at the correct venue.
Quick Answer
Cook County assesses commercial and industrial property at 25% of market value versus 10% for homes, so an over-assessment costs roughly 2.5x more. You appeal first at the Assessor, where anyone can file (including an LLC), then at the Board of Review, where an entity-owned parcel needs counsel.
Why commercial owners pay for an error twice over
Cook County does not assess every property the same way. Homes (Class 2) are assessed at **10% of market value.** Commercial and industrial property (the Class 5 group — 5a commercial, 5b industrial) is assessed at **25% of market value.** The Illinois Constitution lets a county set the top class at no more than 2.5 times the lowest, and Cook sits right at that cap — 25% versus 10% is the 2.5x maximum.
Here is what that means in practice. Assessed value is then multiplied by the state equalization factor — **3.0355 for 2024 (the final figure from the Illinois Department of Revenue)** — before local tax rates apply. So an inflated *market-value* opinion on a commercial parcel flows into the bill at two and a half times the leverage of the same error on a home, and then gets multiplied again by the equalizer. A modest-looking overstatement of your building's value can translate into a meaningful, recurring overcharge. (Assessed value is a value figure, not a tax-savings figure — but it is the lever the whole bill turns on, which is exactly why it is worth reviewing.)
The two venues — and where the rule changes
A Cook County appeal has two separate offices, with two separate windows and two different rules about who is allowed to file.
**The Assessor's Office (first level).** Anyone can file their own appeal here, and that includes business entities. The Cook County Assessor's official appeal rules do not require anyone — individual or LLC — to be represented by an attorney or agent. If your only move is an Assessor appeal, an entity can file it itself.
**The Board of Review (second level).** This is where it changes, and where most owners get it wrong. Under the Board of Review's official rules, only **licensed attorneys** and **individual taxpayers representing property titled in their own name** may practice before the Board. An individual homeowner can still go pro se. But a **corporation, LLC, or condominium association** — and, by the same logic, any other owner that is not an individual holding title in their own name, such as a partnership or trust — **cannot represent itself** at the Board; it must be represented by a licensed attorney, and a non-attorney may not stand in for it.
Most commercial and income property is held in an LLC or corporation precisely for liability and tax reasons. So for the typical commercial owner, the sequence is: optional do-it-yourself at the Assessor, and **attorney-required, not attorney-optional, at the Board of Review.** That is the Board's rule, not a sales pitch — and it is the single fact that should shape how you plan a commercial appeal.
How a commercial appeal actually proceeds
The order of operations for an entity-owned commercial or industrial parcel:
- **Confirm how title is held** — your own name, or an LLC, corporation, partnership, trust, or association. For most commercial property it's an entity, and that one fact decides whether you can self-file at the Board.
- **Pin down your township window.** Cook County has no single countywide deadline. Each township opens and closes on its own staggered calendar, the last-file date is printed on your reassessment notice, and **there is no extension.** For 2026, the South and West suburban townships are in reassessment.
- **Build the value case.** Commercial appeals usually turn on a market-value argument — income/NOI for income property, recent sale, cost, or comparable assessments — not the residential "look at my neighbor's house" approach. The record matters: square footage, class, vacancy, and use all feed the number.
- **File at the Assessor first**, where an entity can file on its own, and then **at the Board of Review with counsel**, where representation is legally required for an entity.
What the record says about commercial appeals
Two things from the public Board of Review record are worth knowing before you start, both as base-rate context rather than any prediction about your parcel:
- Across the **17 South and West townships in the 2026 reassessment, about 20.6% of appeals are commercial or industrial.** Commercial is a minority of filings but a large share of the dollars at stake.
- Historically, **commercial grant base-rates run roughly 37–44%, below the residential rate of about 52%.** Commercial cases are decided on harder evidence, which is part of why they more often run through experienced counsel. These are historical rates from the Board's own record — they describe what has happened, not what will happen on any given appeal.
And the structural tell: **about 86% of Cook County Board of Review appeals are attorney-represented.** At the Board, the commercial market is overwhelmingly a represented market — partly by rule for entities, partly because the evidence bar rewards it.
Where Censum fits
Censum is built for exactly this path. Look up the parcel, see where its assessed value stands and where it sits in the township calendar, and — for entity-owned commercial or industrial property that needs counsel at the Board — get the appeal **prepared and ready for the attorney representation the Board requires,** through Censum's filing rails, on flat pricing. Censum is an independent intelligence and filing-rails vendor — the software the appeal is prepared on. It is **not** Cook County, not a government office, and **not a law firm**: the licensed attorney the Board requires is engaged and paid directly for the legal work, Censum never takes a share of that fee, and Censum does not provide legal representation or give legal or tax advice. The attorney requirement above is the Board's rule, stated as fact, not a Censum add-on.
FAQ
Why is commercial property taxed more heavily than homes in Cook County?
It's the assessment level. Cook County assesses commercial and industrial property (Class 5) at 25% of market value and homes (Class 2) at 10%. The Illinois Constitution caps the top class at 2.5 times the lowest, and Cook is at that cap — so a commercial over-assessment carries about 2.5x the leverage of the same error on a home.
Can I appeal my company's commercial property myself?
At the Assessor's Office, yes — an LLC or corporation can file its own appeal there. At the Board of Review, no. A corporation, LLC, or condo association — and any other non-individual owner, such as a partnership or trust — cannot represent itself at the Board and must be represented by a licensed attorney.
What if I personally own the building in my own name?
Then you can file pro se at both the Assessor and the Board of Review. The attorney requirement at the Board applies to entities — LLCs, corporations, partnerships, trusts, and associations — not to an individual representing property titled in their own name.
How is a commercial appeal different from a residential one?
Commercial appeals usually argue market value through income (NOI), sales, cost, or comparable assessments, and lean on the property record — class, square footage, use, vacancy. Residential appeals more often rest on comparable homes. The evidence bar is generally higher, which is part of why commercial cases tend to run through experienced counsel.
Is Censum a law firm or a tax consultant?
No. Censum is an independent intelligence and filing-rails vendor — the flat-fee software appeals are prepared on. It prepares appeals and gets entity-owned parcels ready for the attorney representation the Board requires; that attorney is engaged and paid directly for the legal work and Censum never takes a share of that fee. It does not practice law, provide legal representation, or give legal or tax advice.
Next step
Start with the parcel, not the paperwork. Look up your commercial or industrial PIN to see where the assessed value stands and where your township sits in the calendar — and, if it's entity-owned and headed to the Board of Review, get it routed toward the representation the Board requires. Censum is independent and is not affiliated with Cook County.