Internalization
From ACT Wiki
1.
The practice where customer trades are executed internally within a brokerage or through intermediaries rather than through an exchange.
The brokerage keeps any money it may make on the spread (the difference between the purchase price and the sale price).
2.
A reduction in the collateral needs of a broker, resulting from the presence of both long and short client positions.
3.
Netting of transactions within a group of businesses, thereby reducing the number and cost of external transactions.
Also written 'internalisation'.