Cook County Property Tax Appeal Deadlines for 2026

By Harsha N Hegde

Cook County has two main appeal windows each year — one through the Cook County Assessor’s Office, and another through the Cook County Board of Review. Both offer homeowners a chance to challenge their property’s assessed value, but the deadlines differ by township and follow separate timelines.

1. Assessor’s Office Appeal Deadlines

The Assessor’s Office opens for appeals first. Each township’s filing window generally lasts about 30 days, beginning soon after reassessment notices are mailed.

For 2026:

• Reassessments will take place in the South & West Suburban Cook County.
• Townships such as Cicero, Stickney, Lyons are open for appeals at this time.
• The North and City townships were reassessed in earlier years, but property owners there can still appeal annually even in non-reassessment years.

You can check the current schedule anytime on the official Cook County Assessor’s Office website.

If you miss your township’s deadline, you must wait for the Board of Review phase.

2. Board of Review Deadlines

The Board of Review is the second stage of the appeal process. It opens after the Assessor has certified assessments for each township. The Board’s schedule also runs township-by-township, typically from late summer through early winter. For the 2026 assessment year, most townships are expected to open for Board of Review appeals between August and December 2026.

You can track filing dates on the Cook County Board of Review portal. The Board accepts online filings and generally gives 30 days to submit your appeal once a township opens.

3. What Happens if You Miss Your Deadline?

Unfortunately, if both appeal windows close, you’ll need to wait until the following year to file again. However, appealing every year — even in non-reassessment years — helps ensure your property value stays fair compared to neighbors. See our related article: Why You Should Appeal Your Cook County Property Assessment Every Year

Can I appeal to PTAB if I miss the Board of Review deadline?

No. To file an appeal with the Illinois Property Tax Appeal Board (PTAB), you must have first filed an appeal with the Cook County Board of Review and received a final decision. PTAB only reviews decisions made by the Board of Review — it cannot accept new cases directly from property owners who missed the Board of Review filing window.

If you miss both the Assessor’s and Board of Review appeal deadlines, your only remaining options are:

• Wait for the next assessment year to appeal again, or
• Pursue a Certificate of Error (CofE) if there’s a clear factual mistake (such as an incorrect property class or exemption issue).

You can file a Certificate of Error through the Assessor’s Office, but it’s limited to specific correction types — not general valuation disagreements.

4. Due Dates for Property Tax Payments

The appeal deadlines are separate from tax payment deadlines.
For reference:

• First Installment 2026 taxes (based on 2025 assessments) will be due around March 1, 2026.
• Second Installment is typically due in August or September 2026, once the final rates are set.

Check your tax bill or the Cook County Treasurer’s website for exact dates.

5. Key Takeaways

• There are two opportunities to appeal every year — first with the Assessor, then with the Board of Review.
• Appeal windows vary by township.
• Missing your township’s window means waiting until next year.
• You cannot go directly to PTAB unless you first appealed to the Board of Review.
• Even if your township isn’t being reassessed, you can still appeal annually to maintain fairness.

FAQs

Is it too late to appeal my Cook County property taxes for 2026?

Not yet — the Assessor’s Office and Board of Review release deadlines on a rolling basis by township.

Can I appeal every year?

Yes. Illinois law allows property owners to appeal annually, even in years when their township isn’t reassessed.

What is the difference between the Assessor’s Office and the Board of Review?

The Assessor’s Office sets the initial assessed values. If you disagree with that value, you can first appeal there. If you’re not satisfied after receiving a decision, you can appeal to the Board of Review.