Cook County, Illinois · Chicago
Cook County property tax appeal guide
Chicago's county, and the only Illinois county that classifies: residential property is assessed at 10% of market value rather than the statewide 33⅓%. Complaints are filed township by township on the dates in each township's notice, so there is no single Cook deadline. Cook is a uniformity jurisdiction: the winning evidence is comparable ASSESSMENTS of similar homes, which is exactly what our per-parcel Cook data produces, and the Board of Review gives every township a second, independent appeal window after the Assessor's closes. The county assesses more than 1.8 million parcels of all classes (Cook County Assessor); our database carries 1.59 million Cook residential Class 2 parcels, measured, which is the residential universe an appeal comparison draws from. You appeal through the Cook County Assessor / Cook County Board of Review; Illinois uses A written complaint to your County Board of Review (Illinois has no statewide form) filed with the County Board of Review.
A free, independent Board of Review complaint is open for these six townships through September 29. This is a second appeal after the Assessor window; supporting evidence is due October 9.
Source: Cook County Board of Review — 2026 Session township open/close schedule (PDF) · verified September 2, 2026Cook runs rolling township-by-township windows. Barrington Township was reassessed on 2026-08-11 and the Assessor accepts appeals through 2026-09-23. Filing with the Assessor is free, and a separate Board of Review window opens later for the same township.
Source: Cook County Assessor — assessment calendar and deadlines · verified August 26, 2026Cook runs rolling township-by-township windows. Bremen Township was reassessed on 2026-08-12 and the Assessor accepts appeals through 2026-09-24. Filing with the Assessor is free, and a separate Board of Review window opens later for the same township.
Source: Cook County Assessor — assessment calendar and deadlines · verified August 26, 2026Cook runs rolling township-by-township windows. Lemont Township was reassessed on 2026-08-17 and the Assessor accepts appeals through 2026-09-29. Filing with the Assessor is free, and a separate Board of Review window opens later for the same township.
Source: Cook County Assessor — assessment calendar and deadlines · verified August 26, 2026Cook runs rolling township-by-township windows. Calumet Township was reassessed on 2026-08-20 and the Assessor accepts appeals through 2026-10-02. Filing with the Assessor is free, and a separate Board of Review window opens later for the same township.
Source: Cook County Assessor — assessment calendar and deadlines · verified August 26, 2026Cook runs rolling township-by-township windows. Hyde Park Township was reassessed on 2026-08-26 and the Assessor accepts appeals through 2026-10-08. Filing with the Assessor is free, and a separate Board of Review window opens later for the same township.
Source: Cook County Assessor — assessment calendar and deadlines · verified August 26, 2026Cook runs rolling township-by-township windows. Leyden Township was reassessed on 2026-08-31 and the Assessor accepts appeals through 2026-10-14. Filing with the Assessor is free, and a separate Board of Review window opens later for the same township.
Source: Cook County Assessor — assessment calendar and deadlines · verified September 2, 2026Cook runs rolling township-by-township windows. Worth Township was reassessed on 2026-09-01 and the Assessor accepts appeals through 2026-10-15. Filing with the Assessor is free, and a separate Board of Review window opens later for the same township.
Source: Cook County Assessor — assessment calendar and deadlines · verified September 2, 2026Dates not yet published by the county. Windows are announced through the year; check the official calendar or leave your address and we watch it for you. Leyden and Worth left this list on September 1 when the county posted their dates, so it does move.
Official calendar: Cook County Assessor — Assessment Calendar and Deadlines (page last updated 9/1/26)- New Trier township: 4,246 homes flagged, a $69.3M assessed-value gap
- Evanston township: 2,536 homes flagged, a $23.1M assessed-value gap
- Oak Park township: 2,507 homes flagged, a $17.0M assessed-value gap
- Norwood Park township: 1,466 homes flagged, a $6.4M assessed-value gap
- Riverside township: 1,120 homes flagged, a $6.1M assessed-value gap
- Rogers Park township: 1,045 homes flagged, a $5.2M assessed-value gap (condo stock undercounted)
- River Forest township: 673 homes flagged, a $7.9M assessed-value gap
Cook County appeal deadline
No single statewide date, Cook County runs township by township; other counties are 30 days after the assessment list is published.
Illinois has no single statewide deadline. In Cook County, complaints are filed township by township on the dates printed in the township's reassessment notices (35 ILCS 200/16-115), so your window depends on where you live and reopens each reassessment cycle. In every other county, the deadline is on or before 30 calendar days after your township's assessment list is published (35 ILCS 200/16-55). Check your county Board of Review's calendar for your township's dates.
How to appeal in Cook County
1. Watch for your township's reassessment notice
In Cook County, townships are reassessed on a rolling three-year cycle and each mails its own notice; your filing window runs from that notice (35 ILCS 200/16-115). Outside Cook, watch for your township's assessment list to be published.
2. File a complaint with the Board of Review
Cook County: file by your township's deadline. Every other county: file on or before 30 calendar days after the assessment list is published (35 ILCS 200/16-55). There is no filing fee. Note that the statute calls this a complaint, not an appeal, at this stage.
3. Build your evidence
Two arguments work. Overvaluation: recent sales of similar homes show your market value is too high, which you prove by a preponderance of the evidence. Lack of uniformity: comparable properties are assessed lower per square foot than yours, which under Kankakee County Board of Review v. Property Tax Appeal Board, 131 Ill. 2d 1 (1989), requires clear and convincing evidence.
4. Board of Review decision
The Board of Review reviews your complaint and may correct your assessment (35 ILCS 200/16-95 in Cook). It issues a written decision.
5. PTAB or Circuit Court (optional)
If you disagree, you may appeal to the state Property Tax Appeal Board within 30 days of the board's written decision (35 ILCS 200/16-160). Alternatively, you may pay under protest and file a tax objection in Circuit Court after exhausting the Board of Review (35 ILCS 200/23-5, 23-10).
Cook County property tax FAQ
What is the property tax appeal deadline in Cook County, Illinois?
No single statewide date, Cook County runs township by township; other counties are 30 days after the assessment list is published. Illinois has no single statewide deadline. In Cook County, complaints are filed township by township on the dates printed in the township's reassessment notices (35 ILCS 200/16-115), so your window depends on where you live and reopens each reassessment cycle. In every other county, the deadline is on or before 30 calendar days after your township's assessment list is published (35 ILCS 200/16-55). Check your county Board of Review's calendar for your township's dates.
What form do I use to appeal in Cook County?
Illinois uses A written complaint to your County Board of Review (Illinois has no statewide form), filed with the County Board of Review. There is no filing fee to appeal.
What is the property tax appeal deadline in Illinois?
There is no single statewide date. Cook County files township by township on the dates printed in each township's reassessment notice (35 ILCS 200/16-115). Every other county runs 30 calendar days from publication of the assessment list (35 ILCS 200/16-55). Check your County Board of Review's calendar.
Other Illinois counties
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