Quick Answer
Three offices touch your number. A local assessor produces the first assessed value. The county's Chief County Assessment Officer reviews and equalizes it. An independent Board of Review hears complaints and corrects assessments "as appears to be just." Knowing which is which tells you exactly where a challenge goes.
Most owners treat "the property tax" as one faceless number that shows up on a bill. It is not one number and it is not one office. Under the State of Illinois' own assessment methodology, the value behind your bill passes through a chain of hands — and each hand has a different job, a different deadline, and a different amount of power to change what you owe. The villain in this story is quiet: an over-assessment that was set once, never questioned, and is now compounding into every bill until somebody makes the machine look at it again.
Here is the machine, in order.
Step 1 — The local assessor produces your number
Outside Cook County, the State assigns "primary assessment responsibility" to township and multi-township assessors. Inside Cook County, an elected County Assessor makes the original assessment instead. Either way, this is the office where your number is born.
A point the IDOR training manual makes bluntly: **the assessor does not create the value of your property.** In the State's words, "the assessor does not create the value of your property. The assessor simply has the statutory responsibility to accurately value property." Value is set in the marketplace — by what buyers and sellers actually do. The assessor's job is to *measure* that value accurately and consistently, parcel by parcel.
What does the assessor actually hold?
- **Your property record card.** The assessor maintains a public record card for every parcel — legal description, land size, building dimensions and types, sales history, and building permits pulled. Per the State, these cards are public information and owners are entitled to view and copy them. If the record says your house has a finished basement it doesn't have, or square footage it doesn't have, that is the assessor's record driving your value.
- **The statutory target level.** Illinois sets a statutory assessment level of "one-third or 33 1/3 percent of market value, unless set otherwise by law" (the State cites Sections 9-145 and 9-175). That 33 1/3% level is in the State's manuals. Cook County is the "set otherwise by law" case: its classification ordinance assesses residential property at roughly 10% and commercial-industrial at roughly 25% — those Cook-specific percentages come from the county classification ordinance, *not* the IDOR training manuals, so treat them as Cook-local and verify against the current ordinance before relying on them.
- **A deadline.** In most non-commission counties, assessors are to complete their assessments by June 15 and certify the books back to the county. After that, for that year, the township assessor can no longer revise your assessment.
That last line matters more than it looks. Once the assessor's window closes, your number moves up the chain — and so does the only place left to fix it.
Step 2 — The county reviews, equalizes, and oversees
The next office is the **Chief County Assessment Officer (CCAO).** In most counties this is a supervisor of assessments; in Cook and St. Clair it is an elected County Assessor. The State defines the CCAO as the official appointed or elected "to assist township assessors in completing original assessments and to review their work," with "the power to revise and equalize assessments." The CCAO is also the Clerk of the Board of Review — the same office sits at the table when complaints are heard.
Two CCAO functions decide whether your number is fair:
- **Review and revision.** The CCAO examines the assessment books, reviews the township assessors' work, and "makes changes when deemed necessary." Your assessor's first number is not the last word at the county level.
- **Equalization.** Illinois requires assessments across areas and classes to sit at the same level. The State defines the equalization factor as the factor "applied to local assessments to bring about the percentage increase or decrease that will result in an equalized assessed value equal to one-third of the market value." If a township is running above or below the statutory level, the CCAO can apply an equalization factor — a multiplier — to bring it into line. Your **Equalized Assessed Value (EAV)** is your assessed value multiplied by the State equalization factor, and the EAV (after qualifying exemptions) is what the tax rate is actually applied to.
For context that lives outside the IDOR manuals: Cook County's 2024 final equalization multiplier was certified at 3.0355. That is an IDOR certification figure, not a training-manual definition — verify the current year's certified multiplier before quoting it. The doctrine in the manual is the durable part: equalization exists so that "the tax burden is distributed fairly among property owners," not to inflate any one bill.
So by the end of Step 2, your number has been produced by the assessor and reviewed-and-equalized by the county. Notice what hasn't happened yet: nobody has heard *your* objection. That is the third office.
Step 3 — The Board of Review hears your complaint
The **Board of Review** is where an owner's challenge actually goes — and the State calls it "the final local authority on local property assessment."
What it is, in the State's own description:
- A **3-member body**, appointed or elected in each county, "to ensure a uniform and equitable local property assessment."
- Members with "experience and training in property appraisal and property tax administration," structured so two members are from one political party and one from another — a deliberately bipartisan, **independent** review body, separate from the assessor who set your value. The CCAO serves as its Clerk.
What it does that you can use:
- **It corrects assessments in both directions.** The board reviews on written complaint that a property "is over assessed or under assessed." A core listed duty is to "lower individual assessments when it is determined the assessments are too high," done "in accordance with Section 16-55 of the Illinois Property Tax Code." It can also raise assessments that are too low — the board cuts both ways, which is exactly why method-grounded evidence matters.
- **It is bound to correct toward fairness.** Section 16-55 of the Property Tax Code, quoted verbatim in the State's township manual, states: "On written complaint that any property is over assessed or under assessed, the board shall review the assessment, and correct it, as appears to be just, but in no case shall the property be assessed at a higher percentage of fair cash value than other property in the assessment district prior to equalization by the board or the Department." The board corrects two distinct things: an assessment set **above market value** (overvaluation), and one set at a **higher percentage of value than other property** in the district (lack of uniformity). In practice, owners prove an over-assessment by comparing their parcel to similar homes — but the statutory yardstick is all property in the assessment district, not "comparable" property alone. If your house is carrying a heavier share of the burden than it should, that is the exact thing the board exists to fix.
- **It runs on a clock.** Assessment complaints "shall be filed on or before 30 calendar days after the date of publication of the assessment list." In counties of 3,000,000 or more inhabitants — that is Cook — the board "shall, from time to time, publish notices which specify the date and place at which complaints may be filed." Miss the window and the machine does not look at your number again until next year.
This is the whole point of understanding the structure: your evidence is wasted on the assessor's counter after June 15, and the CCAO's equalization isn't a venue for a one-parcel argument. The Board of Review is the room built to hear "my assessment is too high" — whether the argument is that the value sits above the market or that it sits at a higher percentage of value than other property in the district — and it is the room with a deadline.
Where you fit — and what to do with this map
Put the chain together and the owner's path is obvious:
- The **assessor** produced your number from a property record card you are entitled to inspect.
- The **county / CCAO** reviewed and equalized it.
- The **Board of Review** is the independent body that will correct it "as appears to be just" — if you bring a method-grounded reason inside the filing window.
The over-assessment doesn't announce itself. It hides in a record card with the wrong square footage, or in a value that sits above the market, or at a higher percentage of value than the property around you. The structure above is not trivia — it tells you which office holds the record, which office holds the equalization math, and which office holds the only door that reopens your number. Walking in knowing the machine is the difference between "I think my taxes are too high" and a complaint aimed at the body that is statutorily required to make it just.
If the property is owned by an LLC, corporation, trust, or condominium association, an attorney is generally required to file at the Board of Review — but this is a board rule and it varies, so confirm the specific board's rules before you file. For any appeal, the practical move is to work with your attorney or a property-tax filing firm; the substance is method and evidence, not paperwork bravado.
Censum exists to hand you the first piece of that evidence: where your assessment actually sits, in plain terms, before any deadline runs. We are independent property-tax intelligence and filing-rails — not the county, not a law firm, and not your counsel of record. Start by seeing the number and where it stands.
FAQ
Who actually sets the value behind my property tax bill?
A local assessor produces the initial assessed value — a township or multi-township assessor in most Illinois counties, or the elected County Assessor inside Cook County. The State is explicit that the assessor "does not create the value" of your property; the market sets value, and the assessor's statutory job is to measure it accurately and consistently. From there the county and the Board of Review review and can revise it.
What does the Chief County Assessment Officer (CCAO) do?
The CCAO assists township assessors, reviews their work, and has "the power to revise and equalize assessments." Equalization means applying a factor — a multiplier — so assessments across areas and classes reach the same statutory level, defined by the State as an equalized assessed value equal to one-third of market value. The CCAO also serves as Clerk of the Board of Review.
What is the Board of Review and why does my challenge go there?
The Board of Review is a 3-member, bipartisan, independent body the State calls "the final local authority on local property assessment." Section 16-55 of the Property Tax Code, quoted in the State's township manual, says that on written complaint a property "is over assessed or under assessed, the board shall review the assessment, and correct it, as appears to be just, but in no case shall the property be assessed at a higher percentage of fair cash value than other property in the assessment district prior to equalization by the board or the Department." That covers two grounds — an assessment above market value and one set at a higher percentage of value than other property — which is why it is the venue built to hear an over-assessment challenge.
What is the deadline to challenge my assessment?
Under the State's rules, an assessment complaint "shall be filed on or before 30 calendar days after the date of publication of the assessment list." In counties of 3,000,000 or more — Cook County — the board publishes notices specifying the dates and place to file, which vary by township. Confirm your township's published window with the Board, because after it closes the assessment for that year generally stands.
Can I just go back to the assessor to fix my number?
Only within the assessor's window. Once the township assessor completes the assessment and certifies the books (by June 15 in most non-commission counties), the State says that assessor "no longer can revise an assessment for that year." After that, corrections route through the CCAO and, for a filed complaint, the Board of Review — which is why the structure, and the deadline, matter.
Does Censum file my appeal or decide my value?
No. Censum is independent property-tax intelligence and filing-rails and acts as Merchant of Record; it is not the county, not a law firm, and not your counsel of record, and nothing here is legal or tax advice. We show you where your assessment sits using the State's method so you can decide whether it is worth reviewing with your attorney or a filing firm. For entity-owned property, an attorney is generally required at the Board of Review — confirm that board's rules.