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. The only date that matters is the one for your township, and it is printed on your reassessment notice.

Outside Cook, Illinois counties use one window: 30 days after the township assessment list is published, with Will County as the worked example below. This guide lists every 2026 date the Cook County Assessor and the Board of Review have published so far, read from their own calendars on September 14, 2026, plus what to do if you missed a window and the 30 day clock for the state Property Tax Appeal Board.

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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.

Which Cook County townships are open with the Assessor right now?

These townships can file an appeal with the Cook County Assessor today. Dates come from the Assessor's assessment calendar, which the county updated on September 14, 2026.

Proviso is the newest row. The county published it on September 14, 2026, the same day its notices went out.

Filing with the Assessor is free and is done online. The Assessor says an appeal "can be done online in as little as 20 minutes." The live countdown for each open township is on our deadline rail and on the Cook County page.

Cook County townships whose 2026 dates are not published yet

As of September 14, 2026 the Assessor has not published 2026 notice or filing dates for these twelve townships: Bloom, Hanover, Jefferson, Lake, Niles, North Chicago, Orland, Palatine, Rich, Schaumburg, South Chicago and Thornton.

If you live in one of these townships, your window has not opened. Your notice will carry the date when it does. Based on the rolling schedule so far, these townships should open between late September and December, but the county has not said so and neither should anyone else. We re-read the Assessor's calendar every few hours and add each township to the deadline rail the day the county publishes it.

Cook County townships whose 2026 Assessor window has closed

If your township is below, the Assessor will not accept a 2026 appeal from you. Your route is the Board of Review window for your township, covered in the next section.

Cook County Board of Review deadlines for the 2026 session

The Board of Review opens townships in groups, and each group gets about 30 days to file plus roughly ten more days to submit evidence. The Board's 2026 session schedule, a PDF the Board regenerated on September 14, 2026, lists two groups so far.

Group 1 hearings are scheduled for October 5 through October 7, 2026. Group 2 is open right now. If you are in Berwyn, Cicero, Elk Grove, Lakeview, Maine or Palos and missed the Assessor window this summer, this is your second chance and it closes September 29.

Every other township, including Lyons, Northfield, Stickney, West Chicago and the nine townships currently open with the Assessor, will get a Board of Review group later in the session. The Board has not published those dates. For scale, the 2025 session's final group, Lake, Orland, Palatine, Schaumburg and Thornton, ran from January 5 to February 3, 2026, so expect the 2026 session to run into early 2027.

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, page updated September 14, 2026, read September 14, 2026.
• 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), file dated September 14, 2026, read September 14, 2026.
• 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.

Deadlines change when the county says they change. We re-read these sources on a schedule and correct this page when they move.