A bill of exchange is a written order from a party (drawer) directing another party (drawee) to pay a specified sum of money to a payee. It must contain an unconditional order to pay a definite amount of money and include a specified time of payment. There are typically three parties to a bill of exchange: the drawer, drawee/acceptor, and payee. A bill of exchange can be used as a written proof of debt and is useful in settling accounts, especially in foreign trade.