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To clear a trade a broker/dealer needs the following four departments: Order Department, Purchase and Sales Department, Margin Department, and a Cashiering Department.

The flow of an order through a clearing firm
1. Order department transmits the order to the appropriate market center for execution.
2. Purchase and Sales Department generates confirmations and matches trades.
3. Margin Department determines whether monies and securities are due.
4. Cashiering department takes delivery of monies and securities.

Introducing firms do not have these departments. They introduce their clients to a clearing firm. This relationship is "fully disclosed" to the customers. For example, on customer statements: "Newport Securities as introduced to National Financial"