Rehypothecation

The practice by banks and brokers of using, for their own purposes, assets that have been posted as collateral by their clients. Clients who permit rehypothecation of their collateral may be compensated either through a lower cost of borrowing or a rebate on fees. 

In a typical example of rehypothecation, securities that have been posted with a prime brokerage as collateral by a hedge fund are used by the brokerage to back its own transactions and trades. While rehypothecation was a common practice until 2007, hedge funds became much more wary about it in the wake of the Lehman Brothers collapse and subsequent credit crunch in 2008-09.