Cook County property taxes are billed in two installments for each tax year, a year in arrears. For Tax Year 2025, the first installment was due Wednesday, April 1, 2026, and the second installment is due Thursday, October 1, 2026 (Cook County Treasurer).
| Tax year | First installment | Second installment |
|---|---|---|
| 2025 (paid in 2026) | Wednesday, April 1, 2026 | Thursday, October 1, 2026 |
| 2024 (paid in 2025) | Tuesday, March 4, 2025 | Monday, December 15, 2025 |
| 2023 (paid in 2024) | Friday, March 1, 2024 | Thursday, August 1, 2024 |
The first installment is an estimate: 55% of the prior year's total tax. The second installment carries the new assessment, the new tax rates and your exemptions, less what you paid on the first. Its date moves from year to year, as the table shows, because the bill can only be issued once the county's assessments and rates are final.
A U.S. Mail payment is on time if its postmark is on or before the due date; a private carrier counts the day it arrives. After the due date, unpaid tax accrues interest of 0.75% a month.
Other Illinois counties set their own due dates; these are Cook County's. For the ways to pay, see how to pay Cook County property taxes, and for what is on the October bill, the 2025 second installment.