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Cook County property tax appeal

Cook County property owners appeal their assessment with the Cook County Assessor while their township is open (usually about 30 days after the reassessment notice), free and online, and then, if needed, with the Board of Review. Open now: Proviso until October 27, 2026; Orland until November 6, 2026; Thornton until November 23, 2026; Rich until December 4, 2026; Lake until October 29, 2026; Palatine until November 4, 2026; Jefferson until November 12, 2026; Schaumburg until November 19, 2026; North Chicago until November 24, 2026; Niles until December 3, 2026; Hanover until December 7, 2026.

Evidence pack for a Cook County property

Property Tax Appeal Evidence Pack, $49. PDF and JSON, usually ready in about a minute. Data only: you file the appeal yourself, directly with the assessing office.

Appeal dates by township

Reassessed in 2026 (south and west suburbs)

Cook County township appeal dates: Reassessed in 2026 (south and west suburbs)
TownshipAssessor appealsNotice mailedLast file dateBoard of Review window
ProvisoOpen until October 27, 2026September 14, 2026October 27, 2026Not posted
OrlandOpen until November 6, 2026September 24, 2026November 6, 2026Not posted
ThorntonOpen until November 23, 2026October 8, 2026November 23, 2026Not posted
RichOpen until December 4, 2026October 21, 2026December 4, 2026Not posted
BloomNot open yet——Not posted
River ForestClosedApril 20, 2026June 2, 2026August 3, 2026 to September 1, 2026
RiversideClosedApril 24, 2026June 8, 2026August 3, 2026 to September 1, 2026
Oak ParkClosedMay 6, 2026June 18, 2026August 3, 2026 to September 1, 2026
BerwynClosedMay 20, 2026July 6, 2026August 31, 2026 to September 29, 2026
CiceroClosedJune 17, 2026July 31, 2026August 31, 2026 to September 29, 2026
PalosClosedJune 3, 2026July 17, 2026August 31, 2026 to September 29, 2026
StickneyClosedJune 29, 2026August 12, 2026Not posted
LyonsClosedJuly 23, 2026September 3, 2026Not posted
BremenClosedAugust 12, 2026September 24, 2026Not posted
LemontClosedAugust 17, 2026September 29, 2026Not posted
CalumetClosedAugust 20, 2026October 2, 2026Not posted
WorthClosedSeptember 1, 2026October 15, 2026Not posted

Not reassessed in 2026 (north suburbs and the City of Chicago)

Cook County township appeal dates: Not reassessed in 2026 (north suburbs and the City of Chicago)
TownshipAssessor appealsNotice mailedLast file dateBoard of Review window
LakeOpen until October 29, 2026September 16, 2026October 29, 2026Not posted
PalatineOpen until November 4, 2026September 22, 2026November 4, 2026Not posted
JeffersonOpen until November 12, 2026September 29, 2026November 12, 2026Not posted
SchaumburgOpen until November 19, 2026October 6, 2026November 19, 2026Not posted
North ChicagoOpen until November 24, 2026October 9, 2026November 24, 2026Not posted
NilesOpen until December 3, 2026October 20, 2026December 3, 2026Not posted
HanoverOpen until December 7, 2026October 22, 2026December 7, 2026Not posted
South ChicagoNot open yet——Not posted
Norwood ParkClosedApril 13, 2026May 26, 2026August 3, 2026 to September 1, 2026
Rogers ParkClosedApril 17, 2026June 1, 2026August 3, 2026 to September 1, 2026
EvanstonClosedApril 22, 2026June 4, 2026August 3, 2026 to September 1, 2026
New TrierClosedMay 7, 2026June 22, 2026August 3, 2026 to September 1, 2026
LakeviewClosedMay 28, 2026July 13, 2026August 31, 2026 to September 29, 2026
MaineClosedJune 5, 2026July 21, 2026August 31, 2026 to September 29, 2026
Elk GroveClosedJune 22, 2026August 4, 2026August 31, 2026 to September 29, 2026
West ChicagoClosedJuly 10, 2026August 21, 2026Not posted
NorthfieldClosedJuly 24, 2026September 4, 2026Not posted
BarringtonClosedAugust 11, 2026September 23, 2026Not posted
Hyde ParkClosedAugust 26, 2026October 8, 2026Not posted
LeydenClosedAugust 31, 2026October 14, 2026Not posted
WheelingClosedSeptember 9, 2026October 22, 2026Not posted

Cook County Assessor's Assessment & Appeal Calendar (updated 10/22/26), refreshed regularly.

How to file (official route)

Cook County Assessor's Office, then the Board of Review. You file directly with this office, by its deadline. Filing is free and you do not need to hire anyone, the Assessor says.

The evidence pack

For one Cook County parcel, from official assessment records: the Assessor's mailed and certified values and the Board of Review's final value for every year published, the characteristics on record, the Assessor's and the Board's past decisions for the PIN, sales of the same class in the Assessor's neighborhood (closest in building area first), the neighborhood's assessment-to-sale ratio, median and COD, and the township's dates. Data only: the pack compiles public assessment and sales records. It is not an appraisal or an opinion of value, not legal or tax advice, and HeritageDeed does not file appeals or represent property owners.

Questions

When is the Cook County property tax appeal deadline?

It depends on the township: each opens when the Assessor mails its reassessment notices and stays open about 30 days. Open today: Proviso (last file date October 27, 2026), Orland (last file date November 6, 2026), Thornton (last file date November 23, 2026), Rich (last file date December 4, 2026), Lake (last file date October 29, 2026), Palatine (last file date November 4, 2026), Jefferson (last file date November 12, 2026), Schaumburg (last file date November 19, 2026), North Chicago (last file date November 24, 2026), Niles (last file date December 3, 2026), Hanover (last file date December 7, 2026). The table on this page lists all 38 townships.

Is it free to appeal property taxes in Cook County?

Yes. The Assessor says filing an appeal is free, can be done online in as little as 20 minutes, and that you do not need to hire anyone to file it. Mailers from tax appeal firms are not from the Assessor.

Can I appeal to the Board of Review after the Assessor?

Yes. Owners can appeal with the Assessor and at the Board of Review; the Board's filing window for each township opens after the Assessor certifies the township and is on the same calendar.

How is a Cook County assessed value calculated?

The Assessor estimates market value; for residential property the assessed value is usually 10% of it, for commercial property typically 25%. Cook County reassesses each township every three years (the south and west suburbs in 2026); the evidence pack converts the published assessed value back to that market value for class 2 and class 5 property only.

What if I missed my township's deadline?

The Assessor says you may appeal the following year when your township opens again, and the Board of Review window may still be ahead: check the table.

Should I appeal?

The Assessor's rule of thumb: if the characteristics on your notice are correct and the estimated market value is within 10 percent of what you think the home is worth, an appeal is unlikely to change the bill much. The evidence pack shows the characteristics on record and what similar homes nearby sold for; the decision is yours.

Order the evidence pack

Property Tax Appeal Evidence Pack, $49. PDF and JSON, usually ready in about a minute. Data only: you file the appeal yourself, directly with the assessing office.

Also free: property history lookup, recently sold homes and the zoning lookup. Buying a property? Order a title search: owner, deeds, mortgages and liens, $49 per report.