What it is:
A clearinghouse is an intermediary between buyers and sellers of financial instruments.
How it works/Example:
Clearinghouses take the opposite position of each side of a trade. When two parties agree on the terms of a transaction, a clearinghouse sits in the middle, acting as both the buyer and the seller. Clearinghouses exist to ensure the smooth functioning of financial markets. Fewer transactions would take place if sellers were worried that buyers would refuse to pay them, and vice versa. A clearinghouse ensures that transactions happen as planned.
For example, if you agree to sell your 100 shares of Company XYZ to John for $10,000, the clearinghouse ensures that John is delivered the 100 shares and you are delivered $10,000. It also records and reports the transaction to everyone involved. Either way, the clearinghouse is responsible for ensuring that the transaction happens in an accurate and timely manner.
Clearinghouses operate in most areas of the business world. For example, in the futures markets, clearinghouses ensure that the buyers and sellers fulfill their obligations related to the futures contract being traded and oversee the proper delivery of the underlying instrument. A country's central bank (e.g. the Federal Reserve in the U.S.) acts as a clearinghouse for checks, interbank payments, foreign exchange transactions, and other fund transfers in the banking system.
Why it matters:
Clearinghouses, acting as middlemen between buyers and sellers, provide both efficiency and stability to the financial markets they serve. However, they take on a high amount of risk because they act as both buyer and seller for a brief moment in almost every transaction. If a buyer fails to pay for the securities he has purchased, the clearinghouse must seek recovery of the funds or wait for them to become available.
Because the clearinghouse is on the hook if either party defaults on their agreement, they generally will not process transactions for traders who take on too much risk. To mitigate risk, clearinghouses also often require traders to deposit additional funds into their brokerage accounts in order to maintain minimum "margin requirements." These funds ensure that the clearinghouse will have access to enough funds to offset losses incurred by traders to get in over their heads and fail to meet their financial obligations.