Why You Should Appeal Your Cook County Property Assessment Every Year

Cook County properties are reassessed once every three years, but you don’t have to wait until your next reassessment to appeal. The Illinois Property Tax Code allows property owners to file an appeal every single year, and doing so can protect you from paying more than your fair share.

Here’s why annual appeals make sense.

1. Errors in property data can persist for years

Assessment records sometimes contain incorrect data such as building square footage, construction type, or lot size. If those errors remain uncorrected, they carry forward each year and inflate your assessed value. Appealing annually ensures these inaccuracies are caught early and corrected promptly.

2. Comparable properties might have received larger reductions

Even if your township isn’t being reassessed this year, your neighbors might have successfully appealed and lowered their assessments.
When that happens, your property can become unequally assessed compared to similar homes on your block — a strong basis for a “lack of uniformity” appeal. Regular appeals help you maintain parity with your neighborhood’s assessment level. Data clearly says appealing yourself has a much higher success rate.

3. Market conditions change every year

Real estate values rise and fall based on market demand, interest rates, and neighborhood trends. A value that was fair last year could now be overstated. By appealing yearly, you can ensure your property’s assessed value stays aligned with current market conditions.

4. Successful appeals can yield multi-year benefits

A reduction obtained in a non-reassessment year can still lower your tax bill for that year and sometimes set a lower base going forward. Waiting for the next triennial reassessment can mean overpaying for two extra years unnecessarily.

5. The law explicitly allows annual appeals

Sec. 35 ILCS 200/9-85 of the Illinois Property Tax Code supports your right to appeal each year:

In counties with 3,000,000 or more inhabitants, the county assessor shall have authority annually to revise the assessment books and correct them as appears to be just; and on complaint in writing in proper form by any taxpayer, and after affording the taxpayer an opportunity to be heard thereon, he or she shall do so at any time, until the assessment is verified.

6. The process is easier than most homeowners think

Both the Cook County Assessor’s Office and the Cook County Board of Review accept appeals online.
Each township has specific filing windows that open once per year:

Filing an appeal takes only a few minutes — and with tools like SquareDeal, you can generate strong comparable-property evidence automatically.

Example Timeline

Year	Reassessment Status	Can You Appeal?	Typical Reason
2025	Reassessment Year	✅ Yes	New market value assigned
2026	Non-Reassessment	✅ Yes	Neighbors’ assessments reduced
2027	Non-Reassessment	✅ Yes	Market softens or property condition changes

Key Takeaway

Even though Cook County reassesses each township only once every three years, you can and should appeal every year if your property is over-assessed or not uniform with similar homes.
Annual appeals help you stay ahead of market shifts, prevent over-taxation, and keep your valuation fair.

About the Author

Harsha N Hegde is the founder at squaredeal.tax, a DIY platform that helps homeowners protest unfair property tax assessments. He has helped thousands of homeowners save money using comps-based evidence and practical guidance.

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Why You Should Appeal Your Cook County Property Assessment Every Year