Fair Assessment

Cook County, Illinois · checked 16 October 2026

Missed the Cook County property tax due date?

The second installment of 2025 Cook County property taxes was due on Thursday 1 October 2026, two months later than usual. If you haven't paid, the cost of waiting is lower than it used to be, but it grows every month.

Want the answer for your own case? Use the tool, then read on for the details.

Check if my home is over-assessed

What being late costs

  • Any unpaid balance is charged 0.75% interest per month from the day after the due date. That's 9% a year.
  • The rate used to be 1.5% a month (18% a year). A 2023 state law cut it in half.
  • Example: on a $3,000 balance, each month late adds about $22.50.
  • Taxes left unpaid for long enough can be offered at the county's tax sale, which adds much bigger costs and puts your ownership at risk. Don't let it get that far.

What to do now

  1. Pay what you can. The Treasurer accepts partial payments, and interest only runs on what's still unpaid.
  2. Pay online for free at cookcountytreasurer.com: search by address or 14-digit PIN and pay from a bank account (you'll need the account and routing number).
  3. Or pay in person at Chase branches across Illinois and more than 100 community banks in the Chicago area.
  4. If you have a mortgage escrow, check with your lender before paying. They may have paid already, and paying twice just creates a refund you have to chase.

Check whether the county owes you money

On the same Treasurer website you can search for refunds (about $105 million was waiting to be claimed) and check for missing exemptions (about $19 million). A missing homeowner or senior exemption is the most common reason a bill is higher than it should be. Exemptions checklist.

Bill too high? Fix next year's now

Paying late doesn't stop you appealing. Your assessment can be appealed whether or not the bill is paid, and several townships are still open with the Assessor this autumn. See if yours is open.

Check if my home is over-assessed

Sources: Cook County Treasurer, 29 September 2026 (due date, 0.75% interest, payment options, refunds and exemptions); WTTW, 18 August 2026. Read 16 October 2026.