Cook County property tax appeal deadlines by township

Each township gets its own dates, reassessment year or not. The Assessor mails assessment notices and then takes appeals until the township's deadline. Later the Board of Review opens the township's complaint window, in groups, with an evidence deadline after it. A Property Tax Appeal Board appeal follows the Board's decision.

Dates come from the Assessor's calendar page (opens in new tab) and the Board of Review's open-and-close PDF (opens in new tab) (version created October 13, 2026, 10:32 a.m. CDT). The Board re-issues that PDF at the same address, so we re-read it at every check.

Download every row as CSV · Add every dated deadline to your calendar (.ics)

Board Rule 8 makes the postmark date the filing date for a complaint sent by mail. Postmarkr letters don't come with a USPS-confirmed mailing date, so file complaints through the Board's own channels, not through us.

Calendar last checked October 13, 2026. We re-check every week while appeal windows are open.

The eight City townships are reassessed again in 2027, and the County hasn't published 2027 dates. In the last City reassessment, the first notices went out on March 18, 2024 and the last Board window closed on February 4, 2025. If 2027 follows that pattern, the first City notices would go out around March 2027 and the last Board windows would close early in 2028. Treat that as a planning guess, and use the County's 2027 dates once they're posted.

Cook County publishes the Assessor's and the Board of Review's parcel data on its open data portal (opens in new tab), and every dataset downloads as CSV. These six cover what an appeal letter needs. Each sample query returned data on October 13, 2026. County queries can take a minute; retry if one times out.

Add a filter to the dataset's CSV address, in this pattern:

https://datacatalog.cookcountyil.gov/resource/uzyt-m557.csv?$where=year=2026 AND township_name='Jefferson'&$order=pin&$limit=50000&$offset=0

Filter on township_name or township_code, never on the first digits of the PIN: those are the area and section, not the township. Open data writes Lake View with a space, where the Assessor and the Board write Lakeview. Page through a large township with $offset=0, 50000 and so on. Some numbers come back with a trailing .0 (year 2026.0, value 16335.0): filter on the number and strip the .0 before you print.

Every dataset says to zero-pad PINs to 14 digits. Spreadsheet apps drop the leading zero, and north-suburban PINs start with 0, so keep the column as text or print it dashed (01-01-100-044-0000). The portal won't join datasets for you, and Parcel Addresses has no township column, so build the list in steps:

1. Parcels and values for one township: Assessed Values for this year and the township, paged 50,000 rows at a time. Drop class EX (exempt) and parcels valued at 0.
2. Prior value: the same dataset for last year, board_tot only. Join it to step 1 on pin in your spreadsheet or script.
3. Addresses: Parcel Addresses for this year, a few hundred PINs per request (the URL gets long), or download the year once and join on pin locally.
4. Optional: remove PINs already in Assessor – Appeals for this year, every name on your do-not-contact list, and names that a recent Parcel Sales buyer has replaced.
5. Deadline: add the township's date from the calendar above.
6. Split the result into files of 100 rows, one file per batch.

Values print exactly as typed, so format money and dates in the CSV. Our CSV import removes a leading -, +, = or @ from every cell, so “-3.2%” would print as “3.2%”: write pct_change in words.

Every merge field needs a value in every row, or that row is rejected. Drop exempt parcels (class EX, value 0) and parcels with no prior-year value before you upload.

We check for duplicates on name and address, so an owner with several PINs at one mailing address gets one letter. List all of that owner's PINs in the one letter, or mail the others in a separate batch.

None of these datasets names an open license. The County's terms of use (opens in new tab) say:

“NO WARRANTY, EXPRESSED OR IMPLIED, IS MADE REGARDING ACCURACY, ADEQUACY, COMPLETENESS, LEGALITY, RELIABILITY OR USEFULNESS OF ANY INFORMATION POSTED ON THE COUNTY WEBSITES. … THE COUNTY PROVIDES THIS INFORMATION ON AN “AS IS” BASIS.”

“DATA CAN ALSO QUICKLY BECOME OUT OF DATE.”

“By use of this system and any data contained therein, you agree that your use shall conform to all applicable laws and regulations and you shall not violate the rights of any third parties.”

The Board of Review dataset's description (opens in new tab) adds:

“All data provided here is prepared for internal purposes by the County of Cook only is provided to the public as a courtesy. … Cook County provides the data for personal use “as is”. The data is not guaranteed to be accurate, correct, or complete. Information provided should not be used as a substitute for legal, business, tax, or other professional advice.”

Lists built from the County's published open data are public records; the sender is responsible for following the professional rules quoted below, honoring every request to stop, and Postmarkr's Acceptable Use Policy. Whether your mailing fits these terms is your decision.

Each rule below is quoted from its official text, with the date we last checked it. We don't say whether a letter meets any of them; that decision is yours. For the labeling and filing rules in other states, see lawyer direct-mail rules by state.

At the Assessor, no representative is required (Rule 5). Before the Board of Review, only attorneys and owners representing themselves may practice (Rule 1).

Rule 7.3(c) names the outside envelope. Postmarkr mails each letter in a double-window envelope, behind an address page we add; your return address prints at the top of that page, in capital letters, and shows through the upper window. A return address can carry a company line of up to 40 characters, printed on its own line under the name. The address form has no company field: import your return address on the Addresses page from a spreadsheet whose company column reads ADVERTISING MATERIAL, then choose it as the batch's return address. You decide whether window display meets your state's rule.

ISBA Opinion 12-04 (opens in new tab) reads the Illinois rule as requiring those exact words: a solicitation labeled “promotional” instead does not meet it. ISBA Opinion 90-37 (opens in new tab) (1991, under the earlier rule) said to label the letter as well as the envelope, and some firms still print the words at the top of the letter too. ISBA opinions are advisory, not binding.

This is a starting point for a property tax appeal solicitation letter, not finished copy. Postmarkr has no shared or starter templates: each firm saves its own. Paste the text below into a new letter template under Templates, write the bracketed parts in your own words, and keep the fields in double braces. Each field must be a CSV column with the same name. A template can hold up to 20 fields.

[Firm letterhead: firm name, office address, phone, website]

Re: Property {{pin}}, {{property_address}} ({{township}} Township)

Dear {{name}},

The Cook County Assessor has mailed a 2026 assessment for the property above. Public records list these assessed values:

After last year's Board of Review: {{prior_value}}
Assessor's 2026 notice: {{new_value}}
Change: {{pct_change}}

These are assessed values, not market values. The Assessor's appeal deadline for {{township}} Township is {{deadline}}. After that, the Board of Review holds its own filing period for the township.

You can file an appeal yourself at the Assessor's office at no cost, and you do not need a lawyer to do so. [Optional line; your firm decides.]

[Firm name] represents property owners in assessment appeals. If you would like us to review your assessment, contact us by {{deadline}} and give your reply code {{code}}: [phone], [email] or [web address]. [State the fee basis exactly as your engagement letter describes it.]

Responsible attorney: [Name], [Firm name], [office street address, city, state, ZIP].

If you do not want letters from us, tell us by [phone/email/web] and quote code {{code}}. We will not write to you again.

[Signature block]

The responsible-attorney line is there for Rule 7.2(a) and the opt-out line for Rule 7.3(b)(1): keep your opt-out list and remove those rows from every later CSV. The template leaves out outcome, refund and savings statements, and anything that could pass for a notice from the Assessor, the Board or the County.

Whether to write again after a letter goes unanswered is your decision. If you decide to, this is the structure:

[Firm letterhead]

Re: Property {{pin}}, {{property_address}} ({{township}} Township)

Dear {{name}},

We wrote to you on [date of first letter] about the 2026 assessment for the property above ({{new_value}}; {{pct_change}} from {{prior_value}}). The Assessor's appeal deadline for {{township}} Township is {{deadline}}.

[Same contact paragraph, reply code {{code}}, fee-basis sentence.]

Responsible attorney: [Name], [Firm name], [office address].

If you do not want letters from us, tell us by [phone/email/web] and quote code {{code}}. We will not write to you again.

Start its CSV from the first one and remove every row that replied, opted out or has already filed (the Assessor Appeals dataset shows filed appeals, with a lag). Refresh the deadline from the calendar.

Today a batch takes up to 100 recipients and $1,000, so a 2,000-letter mailing is 20 batches.

1. Build one CSV per township from the open data: the address columns (name, address_line1, address_line2, city, state, zip) and the 9 merge-field columns.
2. Split it into files of 100 rows. Our CSV import also stops at 500 rows and 25 columns per file.
3. Start a bulk send, choose your saved letter template and upload one file. We check every row's merge fields before you go further.
4. Check the preview of the merged letters and the batch total, then pay by card.
5. Each letter gets a status timeline, with USPS scan updates when available, and a PDF of exactly what was printed.

Postmarkr prints and mails USPS First-Class letters; a one-page black-and-white letter is $2.05 all in. It doesn't send Certified Mail, issue a Certificate of Mailing, give a USPS-confirmed mailing date or include return envelopes.

More guides for law offices are on the law firm mailing hub.