Cook County property tax appeal 2027: deadline, forms and how to file
To appeal a Cook County assessment, file with the Cook County Board of Review online at appeals.cookcountyboardofreview.com, by mail or in person; in Illinois the deadline is 30 days after the township assessment list is published (Cook County uses township filing windows). Confirm the exact date on your notice or with the assessor; we add each county's 2027 date here when it is published.
The Assessor mails a reassessment notice township by township and opens that township for appeals; the notice prints the last date to file. The assessment roll is also published in a print newspaper. 2026 (south and west suburbs reassessed): notices went out from 4/13/2026 (Norwood Park) through 10/8/2026 (Thornton); north-suburb and Chicago townships are opened as their rolls are ready. The Board of Review opens a township after the Assessor has finished it. Cook reassesses on a triennial cycle; City of Chicago reassessment years are 2024 and 2027.
Data as of 20 Oct 2026 · Cook County Board of ReviewCheck your own assessment
Free. We compare the value on your notice with recent sales of similar homes nearby and tell you whether an appeal is worth filing. Have your assessment notice and tax bill handy.
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How to file in Cook County
- Step 1
File the appeal
Online at appeals.cookcountyboardofreview.com with the account number on your notice. State the grounds the county recognises.
- Step 2 · before the hearing
Prepare and submit your evidence
Overvaluation must be shown by a preponderance of the evidence; a uniformity (equity) claim needs clear and convincing evidence. The strongest evidence is a recent arm’s-length purchase of your home, or an appraisal as of January 1. Otherwise use at least three comparable sales, or for equity at least three similar nearby homes with their assessments and property record cards, in a grid. Bring a photo of your home and its property record card.
- Step 3
Meet, then hear
An assessor appeal with Cook County Assessor comes first; if you decline the offer, the Cook County Board of Review hears the case. Most reductions happen at the first step.
Before you file: how to read your notice · evidence that works · informal vs formal hearing · when not to appeal
Forms
| Form | Number | Use | Format |
|---|---|---|---|
| 2026 Real Estate Assessed Valuation Complaint (Board of Review) | — | Paper complaint to the Cook County Board of Review (original filed in person or mailed to 118 N. Clark Street, Chicago). The Board encourages online filing; fax filing is not permitted. A 2027 version was not yet posted as of 2026-10-20. | |
| Residential Property Appeal Form (Assessor, consolidated 2026 fillable) | — | Paper residential appeal to the Cook County Assessor, only when online filing is not possible; anyone filing on behalf of another owner must file online (Assessor Rule 4). Mail or drop off at the address on the form. | Fillable PDF |
| Board of Review online appeal (BOR Portal) | — | Online complaint to the Board of Review; owners can pre-register a complaint before their township opens. A township that has closed cannot be filed until the next year. | Online |
| Assessor online appeal (SmartFile) | — | Online appeal to the Cook County Assessor for residential (class 2), condo/co-op, commercial/industrial, vacant land and omitted-property filings while the township is open. An email address is needed to create an account; a filing ID and docket number are emailed. | Online |
| Attorney Authorization Form, 2027 Session (Board of Review) | — | Authorization an attorney must submit before the complaint is finalized online (Board Rule 2); posted for the 2027 session. Corporations and LLCs must appeal through an attorney; a consultant may not represent a homeowner at the Board. | Fillable PDF |
| General Affidavit 2026 (Board of Review) | — | Supporting affidavit that may be submitted with a Board of Review complaint. | |
| Residential Appeal (Property Tax Appeal Board) | PTAB-1A | Only after the Board of Review decides: the state appeal, due 30 days after the board’s written notice. Can also be filed online through PTAB eFile. | Fillable PDF |
Appeal levels
| Level | Who hears it | Deadline | Cost |
|---|---|---|---|
| Assessor appeal | Cook County Assessor | Date printed on your reassessment notice (township window) | Free |
| Board of Review | Cook County Board of Review | While your township is open (at least 30 days) | Free |
| Property Tax Appeal Board | Illinois Property Tax Appeal Board (state) | 30 days after the Board of Review’s written decision | No filing fee |
| Court | Circuit court (administrative review), or a tax objection in Cook County circuit court | 35 days after the PTAB decision; tax objections follow the tax-bill penalty date | Court costs |
What evidence the board accepts
Overvaluation must be shown by a preponderance of the evidence; a uniformity (equity) claim needs clear and convincing evidence. The strongest evidence is a recent arm’s-length purchase of your home, or an appraisal as of January 1. Otherwise use at least three comparable sales, or for equity at least three similar nearby homes with their assessments and property record cards, in a grid. Bring a photo of your home and its property record card.
Cook County questions
When is the Cook County appeal deadline for 2027?
It depends on your township. 2027 reassesses the City of Chicago: the Assessor opens each township when its notices mail, and the Board of Review then opens it for at least 30 days. Dates are not set in advance; the Assessor’s date is printed on your notice.
How do I appeal my assessment in Cook County?
File online at appeals.cookcountyboardofreview.com, or file the 2026 Real Estate Assessed Valuation Complaint (Board of Review) with the Cook County Board of Review, Board of Review: 118 N. Clark Street, Chicago, IL 60602 (Assessor: 118 North Clark Street, Third Floor, Room 320, Chicago, IL 60602).
Should I appeal to the Assessor or the Board of Review?
Both, if you can. The Assessor’s window comes first and is printed on your notice; the Board of Review opens your township afterwards. A Board of Review complaint is required before you can go to the state Property Tax Appeal Board.
What evidence works best?
A recent arm’s-length purchase of your home or an appraisal as of January 1. Otherwise, at least three comparable sales, or three similar nearby homes with lower assessments, with property record cards and photos.
How do I contact the Cook County Assessor's Office?
Mail: Board of Review: 118 N. Clark Street, Chicago, IL 60602 (Assessor: 118 North Clark Street, Third Floor, Room 320, Chicago, IL 60602). Phone: 312-603-5542 (Board of Review); Assessor 312-443-7550. Hours and walk-in details: cookcountyassessoril.gov.
What if the Board of Review says no?
Appeal to the Illinois Property Tax Appeal Board within 30 days of the board’s written decision. There is no fee, and you can file online through PTAB eFile. A lowered value on an owner-occupied home carries over for the rest of the assessment period.
Check whether yours is over-assessed
Nearby counties
Lake County · DuPage County · Will County · Kane County · Kendall County · McHenry County · Kankakee County
- Cook County Assessor: Assessment and Appeal Calendar (last updated 10/17/26)
- Cook County Assessor: Overview of How Appeals Work
- Cook County Assessor: File an Appeal Online
- Cook County Assessor: Residential Appeals
- Cook County Assessor: Official Appeal Rules
- Cook County Assessor: Residential Appeal Form page
- Cook County Assessor: 2026 Guidelines for Filing Appeals (3.13.2026)
- Cook County Assessor: The Cook County Property Tax System (reassessment years)
- Cook County Board of Review: home
- Cook County Board of Review: Dates and Deadlines
- Cook County Board of Review: 2026 township open/close dates (PDF)
- Cook County Board of Review: Forms
- Cook County Board of Review: Residential appeals
- Cook County Board of Review: Official Rules
- Cook County Board of Review: Frequently Asked Questions
- Cook County Board of Review: online appeal portal
- 35 ILCS 200/16-110 (Cook board of review notice and complaints)
- Illinois State Board of Elections: County Officers directory
- 35 ILCS 200/16-55 — Board of Review complaints
- 35 ILCS 200/12-10 — Publication of assessments
- 35 ILCS 200/16-160 — Appeal to the Property Tax Appeal Board
- Illinois DOR — Assessment Appeals
- Property Tax Appeal Board — Filing your appeal
- Property Tax Appeal Board — FAQ
- needs_verification: deadlineDate: no 2027 township open/close dates published on cookcountyassessoril.gov or cookcountyboardofreview.com as of 2026-10-20; the Board says dates are not set in advance.
- U.S. Census Bureau, county population estimates (2024) and county gazetteer (2024).