19 CFR 111.39: Advice to client.

(a) Withheld or false information. A broker must not withhold information from a client relative to any customs business it conducts on behalf of a client who is entitled to the information. The broker must not knowingly impart to a client false information relative to any customs business.

(b) Due diligence. A broker must exercise due diligence to ascertain the correctness of any information which the broker imparts to a client, including advice to the client on the proper payment of any duty, tax, or other debt or obligation owing to the U.S. Government.

(c) Error or omission by client. If a broker knows that a client has not complied with the law or has made an error in, or omission from, any document, affidavit, or other record which the law requires the client to execute, he must advise the client promptly of that noncompliance, error, or omission. The broker must advise the client on the proper corrective actions required and retain a record of the broker's communication with the client in accordance with §§ 111.21 and 111.23.

(d) Illegal plans. A broker must not knowingly suggest to a client or prospective client any illegal plan for evading payment of any duty, tax, or other debt or obligation owing to the U.S. Government.