The Assessor, the Board of Review & beyond
What is a Certificate of Error in Cook County?
A Certificate of Error is a way to correct a factual mistake on your assessment — like a missing homeowner exemption or wrong square footage — even outside the normal appeal window, and often for prior tax years. The Assessor issues it and the Board of Review certifies it. It fixes errors of fact, not disagreements about value.
If you simply think your value is too high, that is an appeal. If the county has a fact wrong or you were owed an exemption you never received, a Certificate of Error is the right tool.
Check your address — freeSee your own assessment math before you file. You keep 100%.