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. The Assessor tables below are a September 30, 2026 snapshot; the Board of Review table is separately dated. 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.

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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.

Cook County Assessor deadlines checked September 30, 2026

The following filing dates had not passed as of September 30, 2026. This is a dated snapshot, not a live statement that every window below remains open. Verify your township on the official Assessor calendar and use its last filing date, not a guessed number of days after the notice.

Lake, Palatine, Orland and Jefferson now have published dates. Earlier versions of this article listed them as unpublished; the table above corrects that outdated snapshot.

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 dates not listed at the September 30 check

The Assessor calendar did not list 2026 notice or filing dates for these eight townships when checked September 30: Bloom, Hanover, Niles, North Chicago, Rich, Schaumburg, South Chicago and Thornton.

An absent date in this snapshot does not establish your current filing status. Check your notice and the official calendar for newly published dates. Our deadline rail also links to the official sources. Do not wait for an article update to confirm your deadline.

Cook County Assessor dates that had passed by September 30

The regular Assessor filing dates below had passed by September 30. 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 of Review opens townships in groups, and each group gets about 30 days to file plus roughly ten more days to submit evidence. The table below preserves the first two groups from the Board's September 14, 2026 schedule. Both filing dates have now passed. It is not a complete current schedule: check the Board of Review dates and deadlines for later groups and changes.

The September 14 schedule listed Group 1 hearings for October 5 through October 7 and Group 2 evidence due October 9. An evidence deadline is not an extension of the filing deadline: Group 2's September 29 filing date has passed. Confirm evidence and hearing arrangements directly with the Board.

Other townships have separate Board of Review dates. Do not infer them from the Assessor table or from last year's schedule; use the Board's current calendar.

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 September 30, 2026; 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), 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.

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.