What is the Cook County Triennial Reassessment?

Every summer in Cook County, we get our second installment property tax bill for the prior year.  This June, for example, we’re expecting the bill for the second half of last year.  The bills tend to go up a bit each year, but every three years, you open that envelope and recoil.  How could your taxes go up so much?  After all, the last two years they hardly increased at all!  Did they find a platinum mine under your house?

Unfortunately, no.  There’s no platinum mine, nor have you struck gold or oil.  You’ve just been struck by the triennial reassessment. The Cook County Assessor’s office has divided Cook County into thirds, and each year, one-third of the county is reassessed.  One year, the Cook County Assessor’s office reassesses all properties in the City of Chicago.  The next year they reassess the north and northwest suburbs.  And the year after that, they reassess the south and southwest suburbs.  If your area is being reassessed in 2021, you will see the increase (or decrease, but how likely is that?) in your second installment 2021 tax bill.  You won’t get that bill, however, until June of 2022.

So when is your area being reassessed? Check out the chart below and find your township.

Reassessment Years 2021 and 2024


  • Hyde Park
  • Jefferson
  • Lake
  • Lakeview North
  • Rogers Park
  • SouthWest

Reassessment Years 2022 and 2025


  • Barrington
  • Elk Grove
  • Evanston
  • Hanover
  • Leyden
  • Maine
  • New Trier
  • Niles
  • Northfield
  • Norwood Park
  • Palatine
  • Schaumburg
  • Wheeling

Reassessment Years 2023 and 2026

  • Berwyn
  • Lyons
  • River Forest
  • Bloom
  • Oak Park
  • Riverside
  • Bremen
  • Orland
  • Stickney
  • Calumet
  • Palos
  • Thornton
  • Cicero
  • Proviso
  • Worth
  • Lemont
  • Rich

There is a good chance you will see a change in your tax bill the year after you are reassessed.  As the City of Chicago is being reassessed this year, Chicago residents can expect a change in their 2021 tax bill, due and payable in 2022.  Something to look forward to right?