After a transaction is completed, which personal information about a client does NOT need to be destroyed?

The correct response highlights that clients' signatures on stored records do not need to be destroyed after a transaction is completed, as they serve as legal evidence of the agreement and consent in a transaction. Signatures are often important for the validity of contracts and can be required for future reference, audits, or legal purposes.

In contrast, the other types of personal information listed are considered sensitive and should be treated with a higher degree of confidentiality. Clients’ social security numbers, bank account information, and identification numbers can be used for identity theft or fraud, necessitating their destruction to protect clients’ privacy and security post-transaction. By retaining clients' signatures, a firm can ensure necessary documentation is available while also adhering to legal and regulatory requirements.