A clearinghouse is a financial institution that acts as a middleman between buyers and sellers in a market, ensuring that transactions take place even if one side defaults. If one side of a deal fails, a clearinghouse can step in to fill the gap, thus reducing the risk that a failure will ripple across financial markets. In order to do this, clearinghouses ask their members for “margin”–collateral that is held to keep them safe from their own actions and the actions of other members.