The deadline printed on a Cook County assessment notice is the Assessor’s deadline. It is not the last date you can contest your value. Cook County runs two separate first-level appeals—one at the Cook County Assessor’s Office, then one at the independent Board of Review—and it is the Board, not the Assessor, whose decision “sets the final county valuation on the property for that tax year,” in the Board’s own words.
Most homeowners only hear about the first window, because it arrives with a mailed notice. The second opens later, on dates the Board says are “not set in advance.” In the 13 townships whose Board of Review windows have already closed this year, it opened between 27 and 69 days after the Assessor’s window shut. Treat the first as the cheap first try and the second as the one that counts—and put the second on your calendar before the first one closes.
Every township opens for appeals every year, not only in its reassessment year. The Assessor’s calendar says so directly for the off-year townships: “Even though the townships listed below are not scheduled to be reassessed in 2026, property owners still have an opportunity to file an appeal.” So a Wheeling or Palatine homeowner whose value didn’t move this year has a window too. The table below is the Assessor’s calendar as last updated September 29, 2026.
| Township | Calendar section | Notice mailed | Last day to file with the Assessor |
|---|---|---|---|
| Calumet | South & west suburbs (reassessed 2026) | Aug 20 | Oct 2 |
| Hyde Park | North suburbs & City (off-year) | Aug 26 | Oct 8 |
| Leyden | North suburbs & City (off-year) | Aug 31 | Oct 14 |
| Worth | South & west suburbs (reassessed 2026) | Sep 1 | Oct 15 |
| Wheeling | North suburbs & City (off-year) | Sep 9 | Oct 22 |
| Proviso | South & west suburbs (reassessed 2026) | Sep 14 | Oct 27 |
| Lake | North suburbs & City (off-year) | Sep 16 | Oct 29 |
| Palatine | North suburbs & City (off-year) | Sep 22 | Nov 4 |
| Orland | South & west suburbs (reassessed 2026) | Sep 24 | Nov 6 |
| Jefferson | North suburbs & City (off-year) | Sep 29 | Nov 12 |
Thornton, Rich and Bloom (south and west) and Schaumburg, North Chicago, Niles, Hanover and South Chicago (north and City) have not opened yet and show no dates. Lemont, Stickney, Lyons, Bremen, Northfield, Barrington and West Chicago have closed at the Assessor, and the calendar shows no Board of Review dates for them yet. Dates move, so check the Assessor’s calendar and the Board’s dates page for your township before you plan around any of them.
Look at the spacing in that table. Notice-to-deadline runs 43 or 44 days for every open township, and 42 to 47 days for the closed ones. The Assessor’s own FAQ says appellants “typically” have 30 days. The calendar says six weeks. Go by the last-file date on your notice, not by the FAQ’s rule of thumb.
The two appeals look similar from the homeowner’s side and are different institutions. The Assessor sets the value; the Board of Review is, in its own description, “a separate, quasi-judicial agency independent of the Assessor.”
| Assessor appeal | Board of Review appeal | |
|---|---|---|
| Opens | When the township opens; last-file date is printed on your notice | After the Assessor has assessed the township; dates “not set in advance”; pre-registration allowed |
| 2026 length | 42–47 days from notice to last-file date | About 30 days (Aug 3–Sep 1 and Aug 31–Sep 29 in the completed townships) |
| Cost | Free | Free |
| How to file | Online; the Assessor says “as little as 20 minutes” | Online, in person, at satellite offices, or at a Commissioner’s outreach seminar |
| Evidence | Uploaded in the online system; forms vary by property type | Photo of your property required (Rule 18); comps and other documents up to 5 days before the hearing |
| Effect | A determination the Board is “not bound by” | “Sets the final county valuation” for the year |
| Next step | Board of Review | Property Tax Appeal Board (PTAB): petition due within 30 days of the postmark of the Board’s decision notice; no filing fee |
The Board window is easy to miss because nothing on your notice tells you when it is. Across the 13 townships that have finished both stages in 2026, the gap between the Assessor’s last-file date and the Board’s opening day ran from 27 to 69 days, with a median of 49. The Board then kept each township open for roughly 30 days.
| Township | Assessor last-file date | Board of Review window | Days between |
|---|---|---|---|
| Elk Grove | Aug 4 | Aug 31–Sep 29 | 27 |
| Cicero | Jul 31 | Aug 31–Sep 29 | 31 |
| Palos | Jul 17 | Aug 31–Sep 29 | 45 |
| Berwyn | Jul 6 | Aug 31–Sep 29 | 56 |
| River Forest | Jun 2 | Aug 3–Sep 1 | 62 |
| Norwood Park | May 26 | Aug 3–Sep 1 | 69 |
The pattern is that Board windows come in batches, and your township’s batch depends on when the Assessor finished with it, not on when your own Assessor window closed. A homeowner who files with the Assessor in early October and then stops watching could easily have a Board window open and close before the next property tax bill arrives.
Pre-register now. The Board’s FAQ says “You can pre-register your complaint if your township has not opened yet however if your township has closed for appeals this year, you must wait until next year.” If your township is open at the Assessor but not yet open at the Board, pre-registration is the one step that doesn’t depend on guessing a date.
The Assessor appeal is a low-stakes first try, because losing it, or only half-winning it, doesn’t weaken your position at the Board. The Board’s FAQ answers the question directly: “Can I file an appeal even if I have received a reduction with the Assessor’s office? Yes. The Board is not bound by the final determination of the Assessor. You are at no disadvantage if the Assessor has granted or denied a request to reduce the assessment.”
If the Assessor reduces your value to where your evidence says it belongs, you may be done. If it denies you, or gives you a partial reduction, the same evidence package goes to the Board, which decides independently. Nothing in the Board’s FAQ makes an Assessor filing a prerequisite for filing with the Board, so missing the first window isn’t necessarily fatal if your township’s Board window hasn’t opened.
The first window is the loud one. The second is the one with the final say.
Whether either is worth your time is a separate question, and the Assessor is blunt about it: “If the property characteristics on this notice are correct and the estimated market value is within 10 percent of what you think your home is worth then it is unlikely that an appeal would change your property’s assessed value enough to significantly affect its property tax bill.” If your number is inside that band, skip both. If it is well outside, or the property characteristics listed are wrong, build the evidence once and use it twice. The comparable sales guide covers how, and record errors are the easiest case to win.
Individual homeowners can represent themselves at the Board; entities cannot. The Board’s FAQ says properties “held by corporations (LLC, LLP and any other corporate entities) must be represented by counsel” under Board Rule 1. A condominium association must also use an attorney to appeal for the whole building, though individual unit owners may file their own signed appeals.
The Assessor says: “Once you have appealed your reassessment once, 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.” That is a statement about Cook County’s three-year cycle, and it is not how most states work. See why most reductions don’t carry forward before assuming it applies anywhere else.
The Assessor addresses this on its appeals page: “You do not need to hire anyone to file an appeal for you. Filing an appeal is free and can be done online in as little as 20 minutes. You may have received a notice in the mail from a property tax firm… These notices do not come from our office and are sent by firms which charge you a fee based on their estimates of how much they think they can save you.” That is the county’s framing, and there are cases where paying someone makes sense, such as entity-owned property or a large commercial parcel. The DIY-versus-hire matrix and the contingency-fee math lay out the trade, and this guide helps you tell a county notice from a paid solicitation.
An appeal never changes when you pay. The Board’s FAQ asks “Should I wait to pay my taxes until I receive a decision from the Board of Review?” and answers “No.” The first installment is, by law, 55% of the previous year’s total bill and is due March 1. The second installment “cannot be calculated until the Board of Review has concluded its review of every appeal for all 38 townships,” so it arrives only after your decision. The pay-while-you-appeal guide covers the cross-state version.
The payoff also lags by a year. The Assessor says changes “will be reflected in your second installment tax bill the year following your reassessment,” with the example that reassessments received in 2021 affected the bill issued in summer 2022. A 2026 appeal therefore shows up in summer 2027. Even then, a lower assessment doesn’t translate one-for-one: the Assessor notes that a change in your assessment “does not lead to the same increase (or decrease) in your property taxes,” because your bill depends on levies, exemptions and the total assessed value of your community. The Cook County burden-shift post explains why a flat assessment can still come with a rising bill.
If you lose at the Board, the next stop is the Illinois Property Tax Appeal Board. Its FAQ gives 30 days from the postmark of the Board of Review’s decision notice and says “There is no charge for filing an appeal with the PTAB.” See what to do after a denial.
A closed window usually means waiting a year. The Board’s FAQ says “The Board’s jurisdiction is limited by law to the current year,” and the Assessor says that if you miss your period in a reassessment year, “you may appeal the following year when your township is open for appeals.” Since every township opens annually, next year’s window exists. Use the time to gather photos and comparable sales, and read how deadlines work across states so the same thing doesn’t happen twice.
This week, in order
1. Find your township using the Assessor’s township lookup, then find its last-file date on the calendar. 2. Compare your notice’s estimated market value to what you think your home would sell for; if it is within 10%, stop. 3. Otherwise file the free online appeal with the Assessor before the date on your notice. 4. Pre-register a Board of Review complaint if your township hasn’t opened there yet. 5. Photograph the property and collect comparables now, since the Board requires a photo and takes documents up to five days before a hearing. 6. Check the Board’s dates page about a month after the Assessor window closes. 7. Keep paying your bills on time.
What this guide doesn’t settle. Every date and rule here comes from the Assessor’s calendar and appeals page, the Board of Review’s FAQ, and the PTAB FAQ, read on October 2, 2026. We did not find the Board’s published position on whether a Board review can raise an assessment; if that matters for your property, ask Board staff at 312-603-5542 before you file. The state-level framework is in the Illinois property tax appeal guide.
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