Final answer:
An Investment Adviser must record a transaction in a client's account by the end of the next business day after the transaction has been executed, according to U.S. regulations.
Step-by-step explanation:
Under U.S. regulatory standards, an Investment Adviser (IA) is required to record a transaction in a client's account promptly, typically by the end of the next business day after the execution of the transaction. This requirement is part of the Investment Advisers Act of 1940 and the rules around books and records that investment advisers must maintain. These records must be accurate and reflect the transactions in a timely manner to ensure that the IA is acting in the best interest of the client at all times.