Periodically, you'll want to determine the effect changes in exchange rates are having on your business. Even if you make no changes to an unpaid foreign-currency transaction, its value will be affected when exchange rates change. For example, if the US dollar has a higher value at the end of the month than it had when you made your sale or purchase overseas, you'll lose some money on your sales, but you will make money on purchases. On the other hand, if the US dollar is falling in value, sales made earlier in another currency will be worth more in US dollars, but your purchases will cost you more.
Businesspeople generally are concerned with both the potential effect of exchange rates on transactions that haven't been completed yet and the actual effect on them once they've been closed.