The SEC has adopted rules that require “large traders” to register with the Commission and receive unique identification numbers. The traders must then provide their broker-dealers with their ID numbers when they make trades, and the broker-dealers must record the ID numbers as part of their recordkeeping and transaction reporting requirements. A “large trader” is a “person whose transactions in exchange-listed securities equal or exceed two million shares or $20 million during any calendar day, or 20 million shares or $200 million during any calendar month.” Relevant to the Series 79, 62, 55, 7, 26, and Series 24 exams.
Source: SEC Release 2011-154
Further Reading: Analysis by the Securities Technology Monitor