Final answer:
The Bank Secrecy Act requires the use of a Currency Transaction Report for transactions exceeding $10,000 in a single day to combat money laundering and other illegal activities.
Step-by-step explanation:
The federal requirement that mandates the use of a Currency Transaction Report (CTR) if a single customer engages in money service transactions totaling $10,000 in a single day is the Bank Secrecy Act (BSA).
This act requires financial institutions to assist U.S. government agencies in detecting and preventing money laundering.
When transactions meet or exceed this threshold, banks and other financial institutions are required to file a CTR with the Financial Crimes Enforcement Network (FinCEN), which includes information about the transaction and the customer who conducted it. This is to monitor for illegal activities, such as tax evasion or money laundering.