Missed the deadline: your options

First, find out which deadline you missed

Cook County has two separate appeal windows each year. The Assessor's calendar says property owners may file with the Assessor's Office and at the Board of Review, and it lists both sets of dates.

• Assessor window: opens when your township's notices are mailed. The last date to file is printed on your notice.
• Board of Review window: opens later, after the Assessor has finished your township.

If you missed only the Assessor's date, the Board of Review may still be ahead of you. The box at the top of this page shows which townships are open now, and our deadlines page lists every township.

Missed the Assessor? Look to the Board of Review

The Board of Review opens townships for appeals after the Assessor has assessed them. Its FAQ says dates "vary annually" and "are not set in advance," and that "All townships are opened a minimum of 30 days."

If your township has not opened at the Board yet, you can pre-register through the Board's online portal. The Board says pre-registering "ensures that a homeowner's appeal will be on time." You need 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. Dates for the rest will be posted as they open.

Filing at the Board is free, and its staff can help with your appeal. The Board requires a photo of the property you are appealing.

Are late filings accepted?

At the Assessor, no. Its rules call township closing dates "hard" deadlines and say it will not accept any appeal or evidence after the closing date, except in cases of an Assessor system error. If that happened to you, keep proof such as screenshots or an error email.

At the Board of Review, a mailed complaint counts as filed on the U.S. Postal Service postmark date. We found no rule allowing late filings, so treat the close date as a hard deadline.

Once a township closes at the Board, its FAQ says owners "must wait until the next assessment year to file an appeal." The Board also cannot hear appeals for prior years.

Both windows closed? A Certificate of Error may help

A Certificate of Error is the Assessor's way to correct a bill after the assessment for that year is final. There are two kinds: one for missing exemptions, and one to correct a property's assessed valuation.

The Assessor's 2026 guidelines say a Certificate of Error for valuation "may be filed for any reason that a current year assessment appeal may be filed." They strongly recommend filing it together with a current-year appeal in SmartFile. A standalone request can wait several months before it is entered.

There is a time limit. The guidelines quote state law: no such certificate "shall be executed for any tax year more than 3 years after the date on which the annual judgment and order of sale for that tax year was first entered."

Keep expectations realistic. Requests can be denied, and if you already appealed that year at the Assessor or the Board, a request based only on a difference of opinion about value is less likely to succeed. Factual errors, such as wrong square footage, or damage from a fire or flood are stronger.

Missed an exemption instead?

If you qualified for an exemption but it was not on your bill, the Assessor's Certificate of Error page offers a refund route. It currently lists tax years 2025, 2024, 2023, 2022 and 2021 for homestead exemptions such as the homeowner, senior and Senior Freeze exemptions.

You need a photo ID and proof that you were eligible in each year you claim. The Senior Freeze must be filed every year, so a missed year is a common gap.

See our guide to Certificates of Error for missed exemptions and our exemptions guide.

What to gather now

Whichever route is still open, the same papers help. Gather them now so you can file the day a window opens.

• Your 14-digit PIN and any Assessor notice for the property.
• A dated photo of the outside of your home. The Board of Review requires one.
• Proof of any wrong facts on your record, such as square footage or building details.
• If you bought within two years of January 1 of the appeal year, your closing papers. The Assessor's rules require you to disclose the sale date and price.
• A short list of similar homes nearby and their assessed values.

The Assessor requires all supporting evidence to be filed by the township closing date, not afterward. Our guide to choosing comparables helps with the last item.

Already through the Board of Review?

If the Board has decided your appeal and you disagree, you may go further to the Illinois Property Tax Appeal Board (PTAB) or circuit court. The Board's FAQ says this comes after first appealing to the Board.

A PTAB petition "must be filed within 30 days of the postmark date" of the Board's written decision notice. PTAB says late appeals are rejected, and there is no fee to file.

Our PTAB guide covers the next steps.

Keep paying your bill

Do not hold back payment while you sort this out. The Board of Review says not to wait for its decision to pay, and PTAB says taxes still come due during an appeal.

Any reduction from a later appeal or a granted Certificate of Error would come back as a lower future bill or a refund.

How not to miss it next year

The Assessor puts it simply: "If you missed your appeal period in a previous year, you may appeal the following year when your township is open for appeals."

1. Find your township with the Assessor's address search.
2. Bookmark our deadlines page and the Assessor's calendar.
3. Open any Assessor notice the day it arrives. The last file date is printed on it.
4. Pre-register at the Board of Review once pre-registration opens for the year.
5. Check your home ahead of time so you are ready to file the day your township opens. You can check your home free.

If an appeal is granted and nothing about the property changes, the Assessor says the new value stays in place until the next reassessment.