Second-installment property tax bills for tax year 2025 were due Thursday, October 1, 2026; an unpaid balance now accrues interest of 0.75% a month. The Cook County Treasurer posted about 1.8 million bills online on August 18 and mailed them on or before September 1. You do not need the paper bill to pay: search by 14-digit PIN or address on the Treasurer's site, pay from a bank account free, or by card with a 2.08% fee.
The 2025 tax year schedule
| Installment | Covers | Due |
|---|---|---|
| First installment 2025 | 55% of the 2024 total bill, an estimate | April 1, 2026 (extended from March 1) |
| Second installment 2025 | The balance: the 2025 assessment, the 2025 rate and equalizer, and your exemptions, minus the first installment | October 1, 2026 |
| First installment 2026 | 55% of the 2025 total | due date set by the Treasurer early in 2027 |
Cook County bills a year in arrears, so the bill due October 1, 2026 is for tax year 2025. It is the first bill that reflects the 2025 assessment for townships reassessed in 2025 (the north suburbs) and the exemptions granted for 2025.
Why the second installment can be bigger than the first
The first installment is a flat 55% of last year's total bill. The second carries everything that changed since: the new assessment, the new tax rate and equalizer, and any exemption added or lost. A reassessment, a rate increase or a missing exemption shows up in full on the second installment. If yours jumped, check the exemptions first, then the assessment behind them.
Read the bill before you pay it
- Exemptions. The Homeowner Exemption ($10,000 of equalized value), Senior Exemption ($8,000), Senior Freeze, Disabled Persons and Veterans exemptions print on the bill. A missing one is corrected with a Certificate of Error through the Assessor and refunded by the Treasurer, not by an appeal. See how a Certificate of Error works.
- Assessed value and equalizer. The 2025 equalizer is 3.03. The assessed value should match your 2025 notice or, if you appealed, the reduced figure.
- Rate. Composite 2025 rates run from about 6.4% in New Trier to 19.0% in Thornton; Chicago is 6.85% in most of the city. See 2025 rates by township.
- Escrow. If a lender pays from escrow the bill still shows online under your PIN; check it anyway, because exemptions and assessment errors are yours to catch.
What late payment costs
Unpaid balances accrue 0.75% per month, 9% a year, for tax year 2023 onward under Public Act 103-555. Interest is charged by the month or part of a month with no daily proration: on a $6,000 balance, one day late costs the same $45 as thirty days late. Partial payments are accepted and reduce the balance that accrues interest.
This bill cannot be appealed. Next year's can.
The October 1 bill is closed: the 2025 assessment was appealable in 2025 and the 2025 rate is set. What you can change is the 2026 assessment behind next year's bill, and for the south and west suburbs 2026 is a reassessment year with median increases of 20–27% (see the township numbers). The Assessor's 2026 windows run township by township through the fall, the last closing in late November (Schaumburg November 19, Thornton November 23); the Board of Review follows each township after the Assessor certifies it, and it is open now for West Chicago, Lyons, Northfield and Stickney, through November 6. The deadlines page has every township.
To see what your bill would have been at a corrected assessment, run the free property check; it shows your bill history for 20 years alongside the assessments that produced it. If you cannot find your bill online, see how to look up a Cook County tax bill.
