When the entity that contracts with the client is also the booking entity, the choice of booking entity determines the entity that is the party to the trade, how much can be offset on close-out netting, and with whom collateral is delivered. Otherwise, the entity that contracts with the client is the sales entity, and it enters into an intragroup trade with the booking entity. FSA materials use the phrase "booking entity" for the group company that carries a trade, and "booking strategy" for the purpose of moving trades within a group.
On this site, "booking" means deciding which legal entity's books carry a trade. It is a different meaning from trade capture, which is recording an executed trade in a system. The "accounting branch" that the FSA uses in supervising foreign bank branches is not a legal entity but the branch that manages the trades.