Assessor or Board of Review: where to appeal and when

The short answer

Start with the Cook County Assessor's Office if your township is open there. Then, if you are not satisfied, file with the Cook County Board of Review when it opens your township.

You do not have to choose. The Board of Review says it is not bound by the Assessor's decision, and you are at no disadvantage whether the Assessor granted or denied a reduction. Filing is free at both.

Two offices, two jobs

The Assessor sets the taxable value on all of the more than 1.8 million parcels in Cook County. Each year it reassesses one part of the county, and in 2026 that was the south and west suburbs.

The Board of Review is a separate, quasi-judicial agency, independent of the Assessor. Under Illinois law, on a taxpayer's written complaint it reviews the assessment and can confirm, revise, correct, alter or modify it. Its decision sets the final county valuation on your property for that tax year.

Neither office sets your tax rate. The Assessor says it does not set levies, rates or bills, and the Board notes that exemptions, local levies and tax rates also shape your bill.

Side by side

The table sums up what each office's own rules and pages say for homeowners.

Based on the Assessor's appeal rules and online-filing pages, and the Board of Review's rules and FAQ. Procedures can change; check each office's current page before filing.

Timing: what usually comes first

Your township opens at the Assessor when its assessment notices are mailed. The last date to appeal there is printed on your notice and on the Assessor's calendar, and the Assessor treats it as a hard deadline.

The Board of Review opens townships after the Assessor has assessed them. It says filing dates vary every year and are not set in advance, and that "All townships are opened a minimum of 30 days." You can pre-register online before your township opens, using your township, name, property address and PIN.

As of early October 2026, the Board had published dates only for its first two groups of townships. Our deadlines page adds the rest as they are announced.

Why it can make sense to use both

Each office looks at your case separately, and their evidence rules differ. If the Assessor lowered your value, you can still ask the Board of Review to look again. If the Assessor said no, the Board is not bound by that answer.

What makes either appeal strong is the same: comparable homes in your neighborhood that resemble yours in size and style, proof of any wrong characteristic, and filing before your township's deadline. Many appeals end with no change, so clear evidence matters. A free check against similar homes is a quick way to see whether your assessment looks out of line.

Which one fits your situation right now

• Your township is open at the Assessor. File there now. The Board of Review stays available as a second chance later.
• The Assessor has closed, the Board has not opened yet. Pre-register with the Board online and use the time to gather comparables and a photo.
• Both windows have closed. The Board says you must wait until the next assessment year. A factual error in your record can still go to the Assessor.
• You have a Board decision you disagree with. You can ask for a Re-Review within 3 days of the decision letter, or appeal to PTAB within 30 days of the postmark date on the decision notice. See PTAB after the Board of Review.

Can the Board of Review raise my assessment?

The law lets the Board revise an assessment in either direction. But it says an assessment cannot be increased unless the taxpayer is first notified in writing and given a chance to be heard.

In practice, increases are rare. Our calculation from the same open dataset found 14 increases among 81,783 self-filed residential overvaluation appeals for tax year 2025.

Prior years: only one office can help

The Board of Review cannot change a past year: its jurisdiction is limited by law to the current year. A closed Board of Review window means waiting until the next assessment year.

For factual errors in earlier years, such as wrong square footage, the Assessor handles Certificates of Error. The Assessor's 2026 guidelines say that if you are unhappy with a Board of Review decision, the right path is PTAB or the Circuit Court, not a Certificate of Error. See Certificates of Error for missed exemptions.

Evidence you can reuse

The core of your case is the same at both offices: comparable homes with their PINs, recent sale documents, or proof that a characteristic is wrong. See how to pick comparables.

For the Board of Review, add a short written brief and a recent color photo of the front of your home. The Board's staff can help you organize your file, and its hearings for self-represented homeowners are held by phone. For the full filing walk-through, see how to appeal step by step.