Illinois Property Tax Appeal Deadlines 2026, Township by Township

If you searched for the Cook County property tax appeal deadline, you found a dozen different answers. That is because there are dozens of deadlines. Cook County runs appeals township by township, and every township gets two separate windows each year: one at the Cook County Assessor and a second, later one at the Cook County Board of Review. Confirm your township, assessment year and filing office. An Assessor notice does not establish the separate Board of Review deadline.

Outside Cook, Illinois counties use one window: 30 days after the township assessment list is published, with Will County as the worked example below. The current Assessor table below was checked November 3, 2026; historical closed dates are separated from the current filing windows. Check the official calendar before filing, because new dates can be published after this article is checked. This guide also covers missed windows and the 30 day clock for the state Property Tax Appeal Board.

Current filing dates checked November 3, 2026. South Chicago Township's Assessor window runs through December 15. The separate Board of Review Group 3 filing window closes November 6, only for Lyons, Northfield, Stickney and West Chicago. Confirm your actual township rather than assuming a neighborhood name identifies it.

Before buying help: Filing with either Cook office is free. Use the official Assessor calendar or Board schedule to confirm the correct route. Our free Cook address check shows available records and supported findings; a match alone does not establish an appeal case. Preview the worked Illinois kit example before considering the optional $29 guide and workbook. You gather and verify its evidence and file yourself. The separate $49 Audit depends on county/address evidence and supplies the filing or valuation output those findings support. Neither product files for you or guarantees savings.

Why Cook County has no single deadline

Cook County reassesses each property once every three years. The Assessor's calendar splits the county into two groups, South and West Suburban Cook County, and North Suburbs and City of Chicago, and in 2026 every township in both groups gets its own appeal window with the Assessor, reassessment year or not.

The Assessor's own guidance is plain: "Typically, you have 30 days to file an appeal after receiving your reassessment notice. The last date to file an appeal for that year is printed on your notice." In practice the 2026 windows have run 42 or 43 days from the notice date to the last filing date. Do not compute your own deadline from that pattern. Use the date on your notice or in the table below.

After the Assessor's window closes, the same township later gets a second window at the Board of Review. In the Board's own words, it "is a separate, quasi-judicial agency independent of the Assessor," it "is not bound by the final determination of the Assessor," and "you are at no disadvantage if the Assessor has granted or denied a request to reduce the assessment." You do not need to have filed with the Assessor to file with the Board of Review, and filing at both is free.

Cook County Assessor windows open at the November 3 check

These are the dates on the official Assessor calendar, checked November 3. This is a dated snapshot, not an automatic extension or a promise that a listed window is still open when you read it. Use the current official last-file date and save your submission confirmation.

Earlier versions listed seven of these townships as awaiting dates. Their dates are now published. November 4 update: Bloom's newly published notice date is November 3 and its last filing date is December 17, independently checked on the official calendar. All 38 townships now have published Assessor dates; that does not mean every window remains open. The Cook County guide and deadline directory provide the site's current source-linked window listings.

Cook County Assessor dates that had passed by November 3

The regular Assessor filing dates below had passed by November 3. Check the separate Board of Review schedule for your township; an Assessor deadline does not establish whether the Board of Review window is open.

Cook County Board of Review deadlines for the 2026 session

The Board uses its own calendar, independently of the Assessor. Its 2026 session schedule and official Group 3 announcement, rechecked November 3, list these groups. Groups 1 and 2 are retained as closed historical context.

November 16 is the evidence deadline for a timely Group 3 complaint, not an extension of the November 6 filing window. Check current evidence instructions and save the Board's filing receipt. Do not use South Chicago's December 15 Assessor date to file a Board complaint; it is a different office and township scope. Check the Board's current dates and deadlines for other groups or changes.

The Board of Review complaint is filed online and is free. Cook County publishes its own complaint form and rules on the Board of Review site rather than a statewide form. Illinois has no statewide appeal form at all.

What happens if I missed both Cook County windows?

It depends on which window you missed.

Missed the Assessor, Board of Review still ahead. File at the Board of Review when your township's group opens. It is an independent appeal, it takes the same evidence, and it is open to every parcel once per tax year whether or not you filed with the Assessor.

Missed the Board of Review too. The 2026 assessment stands, and the next chance is the 2027 Assessor window for your township. There is no late filing at either body. The state Property Tax Appeal Board cannot help here, because PTAB only hears appeals from a Board of Review decision.

Filed at the Board of Review and lost. The Board's FAQ says that "after first appealing to the Board of Review, you may choose to appeal further to the Cook County Circuit Court or the Property Tax Appeal Board (PTAB)." Most homeowners choose PTAB, and the clock is short. PTAB's rule: "A petition for appeal to the PTAB must be filed within 30 days of the postmark date of written notice of the board of review's decision." There is no charge for filing with PTAB. Residential owners use PTAB's residential appeal form (PTAB-1-A), and written evidence goes in with the form; if it is not ready, you must request an extension in writing when you file. PTAB warns that "the time frame required to resolve such appeals is difficult to project," and its decisions are reviewable in court under the Administrative Review Law.

Owners waiting for a 2027 window can prepare now. The worksheets in the $29 Illinois kit are built for that: review your property record, list the errors to investigate and plan your evidence before the window opens. The kit does not find comparables for you and does not file anything; it organizes the work.

Will County property tax appeal deadline 2026

Will County is simpler than Cook, but its 2026 window has already closed. The Will County Board of Review complaint portal states: "The Board of Review Complaint Portal will be open for new complaint submissions from August 12, 2026 through September 14, 2026." That matches the statewide rule for counties outside Cook: a complaint must be filed within 30 days after the township assessment list is published (35 ILCS 200/16-55).

Two Will County specifics worth knowing for 2027. Every complaint must include a written argument, and starting in 2026 any attorney filing on an owner's behalf must have a notarized authorization on the county's current form. If you filed by September 14 and receive an unfavorable decision, the same 30 day PTAB clock above applies.

What evidence wins a Cook County residential appeal?

The Assessor's residential appeal page says the most common basis is uniformity: your home is assessed higher than comparable homes nearby. Its instruction on comparables is specific. "Select homes within your neighborhood code that closely resemble your own home in both size and style. If you submit homes that are very different from yours, they will not be considered as comparables."

Two other grounds are accepted. Overvaluation, supported by "recent closing statements, or purchase prices of homes similar to yours." And incorrect property information, supported by "dated photos, a property deed, or other evidence." Our guides on finding comparables and on whether your house is over-assessed cover how to build each of these.

The uniformity case is the one our Cook County data is built for. The free calculator pulls the assessed values of similar homes in your neighborhood from the county's roll, which is exactly the comparison the Assessor and the Board of Review ask for.

Do I have to appeal every year in Cook County?

No. The Assessor states: "Once you have appealed your reassessment, you do not need to do it each year, unless the characteristics of your property have changed significantly due to new construction, demolition, vacancy, or other issues." Appealing again in a non-reassessment year is allowed, since every township gets a window every year, and it can make sense if comparable assessments around you dropped or your property record has an error.

How do I find my Cook County township?

Your township is printed on your reassessment notice and on your tax bill. If you do not have either, search your address on the Cook County Assessor's website and the township appears in the property details. Our Cook County page shows which windows are open today for each township once you have the name.

Sources

• Cook County Assessor, Assessment Calendar and Deadlines, checked November 3, 2026; current and closed Assessor tables updated from that check.
• Cook County Assessor, Overview of How Appeals Work and Residential Appeals pages, read September 14, 2026.
• Cook County Board of Review, Dates and Deadlines 2026 Session (township open and close schedule PDF), re-read November 3, 2026 for Group 3 filing and evidence dates; Groups 1 and 2 retained as historical context.
• Cook County Board of Review, Frequently Asked Questions, read September 14, 2026; historical dates for the 2025 session, read August 12, 2026.
• Illinois Property Tax Appeal Board, Filing Your Appeal and Frequently Asked Questions, read September 14, 2026.
• Will County Board of Review complaint portal, read September 14, 2026.
• 35 ILCS 200/16-55 and 35 ILCS 200/16-110, Illinois General Assembly.

The county controls filing dates. This article contains dated checks; always confirm the current official calendar and your notice before filing. The Board of Review, PTAB and Will County sources above retain their separately stated review dates.