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Can I appeal a prior year’s assessment?
Generally no—you can't file a regular appeal for a prior year after the deadline passes. But a Certificate of Error may correct a verifiable factual mistake (wrong square footage, non-existent/demolished structure, misclassification, wrong unit count), applying to the current year and up to three prior years, possibly with a refund. A COE can't be used merely because you think the value was too high or you missed the deadline.
Are You Overpaying?
Is your assessment too high? Check your potential savings in under a minute.
ATTORNEYS & CPAs, EVERY VENUE
In 2025 our clients were 1.7 times as likely to win a reduction at the Assessor, and 1.3 times as likely at the Board of Review, as clients of attorneys with 100+ decided residential appeals (2.2 times at the Assessor in 2026 so far, as of October 29, 2026).
Instant property analysis from county data
Licensed Illinois tax attorneys & CPAs
Every level: Assessor → Board of Review → PTAB or Circuit Court
Source: Cook County Assessor and Board of Review public appeal records. Past results do not guarantee a similar outcome.
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$0 Upfront cost — no fee unless your assessment is reducedOur fee is 25% of first-year savings, only if your assessment is reduced.
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