Cook County property tax due dates — and why this year's bill is late
Verified against the Cook County Treasurer's official dates as of July 2, 2026. The headline: the Tax Year 2025 second-installment bill — the one that reflects new assessments — is running about two months late, expected around September 2026.
Official due dates
| Tax year | Installment | Due date |
|---|---|---|
| 2025 | Second | Not yet announced — officials say ~2 months late; bills expected around September 2026 |
| 2025 | First | Wednesday, April 1, 2026 |
| 2024 | Second | Monday, December 15, 2025 |
| 2024 | First | Tuesday, March 4, 2025 |
| 2023 | Second | Thursday, August 1, 2024 |
Always confirm on the Treasurer's Important Dates page — dates above were checked July 2, 2026.
Why the second installment matters more
The first installment is simple: it's 55% of last year's total bill, no matter what happened to your assessment. All the real news — your reassessment, exemption changes, the new state equalizer, and local tax rates — lands in the second installment. That's the bill that jumps.
Why recent bills jumped
On the most recent completed bills (Tax Year 2024, due December 2025), the average Cook County homeowner increase was about 16% — and some Chicago West and South side neighborhoods averaged over 100%, per county officials and reporting by WTTW. The Tax Year 2025 bills arriving around September 2026 carry the North suburbs' 2025 reassessment; the South and West suburbs are being reassessed in 2026, with those changes hitting bills in 2027 — but their appeal windows are open township-by-township right now, when notices arrive.
What you can do about it
You can't change the due date, but you can check the number behind the bill. Two minutes with your PIN tells you what your new assessment means in dollars — and whether it rose more than comparable homes in your tax code, which is the basis of an appeal:
→ Estimate your new bill (PIN auto-fill)
→ Check you're getting every exemption you qualify for
Think your assessment is too high? A licensed appeal service can check for free.
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See how much I could saveOwnwell is a licensed appeal service. There's no upfront cost to check — they only charge if they win you a reduction.