Challenge: Banks, brokers, and dealers in the forex markets allow a high amount of leverage, which means that traders can control large positions with relatively little money of their own. Leverage in the range of 100:1 is a high ratio but not uncommon in forex. A trader must understand the use of leverage and the risks that leverage introduces in an account. Extreme amounts of leverage have led to many dealers becoming insolvent unexpectedly.
The broker basically resets the positions and provides either a credit or debit for the interest rate differential between the two currencies in the pairs being held. The trade carries on and the trader doesn't need to deliver or settle the transaction. When the trade is closed the trader realizes their profit or loss based on their original transaction price and the price they closed the trade at. The rollover credits or debits could either add to this gain or detract from it.
One unique aspect of this international market is that there is no central marketplace for foreign exchange. Rather, currency trading is conducted electronically over-the-counter (OTC), which means that all transactions occur via computer networks between traders around the world, rather than on one centralized exchange. The market is open 24 hours a day, five and a half days a week, and currencies are traded worldwide in the major financial centers of London, New York, Tokyo, Zurich, Frankfurt, Hong Kong, Singapore, Paris and Sydney—across almost every time zone. This means that when the trading day in the U.S. ends, the forex market begins anew in Tokyo and Hong Kong. As such, the forex market can be extremely active any time of the day, with price quotes changing constantly.