The original due date to file and pay Illinois individual income tax for calendar year filers is April 15, 2025. Cook County Treasurer's Office - Chicago, Illinois.The due date for Tax Year 2024 First Installment is Tuesday, March 4, 2025. Make a payment online. Tax Year 2024 First Installment Property Tax Due Date: Tuesday, March 4, 2025 ; Tax Year 2023 Second Installment Property Tax Due Date: Thursday, August 1, 2024. Simply click the "Set up a Payment Installment Plan with IDOR" link. The Department of Finance offers payment plans to motorists with outstanding parking, compliance, red light camera or automated speed enforcement violations. All due dates assume that the date falls on a business day. If the due date falls on a holiday or weekend, the due date will be the next business day. Payment is due on the 28th of each month unless you are enrolled in the optional UI-Pay Payment Plan.