An invoice in foreign currency exists if the currency in the invoice is different from the local currency defined for your company code.The buyer enters the currency that is used when placing a purchase order with a foreign vendor in the purchase order itself. Usually you receive an invoice in the currency specified in the purchase order, but you can also enter the invoice in a different currency.An exchange rate between the foreign currency entered and your local currency must be stored in the system. You can define different exchange rates for different periods.