What must an EA do after finding a client return error?

The EA should promptly advise the client of the error, omission, or noncompliance and explain the potential consequences. That is the core Circular 230 duty when the practitioner knows of a client error.

The advice should be concrete. Identify the affected return or form, explain why the prior position may be wrong, describe possible tax, penalty, interest, or carryforward effects, and recommend a correction path if correction is appropriate. The EA should also document the communication and the client's decision.