Navision allow you to create customer with foreign currency. To speficy the currency for a customer, open the Customer Card. Select the Foreign Trade tab.
Whenever we deal with foreign currency, of course we will have currency exchange rate. Navision allow users to maintain currency exchange rate by date. To maintain the currency exchange rate, Click on Financial Management --> General Ledger --> Periodic Activities --> Currency --> Currencies. Select a currency code and then click on the Exch. Rates.
Navision will picked the exchange rate based on the posting date of your document. For example, if you post an invoice before 01/01/1999, Navision will take 3.592419 as the exchange rate. If you post an invoice on 2/1/2000, then Navision will take 2.40 as the exchange rate. Cool isn't it ? As long as you maintain the exchange rate, Navision will be able to pick the exchange rate accordingly.
How if you forgot to update the exchange rate but have posted an invoice. For example, you forgot to maintain the 2nd line from the example above (01/01/2000) and you posted your invoice on 2/1/2000. Navision will take the exchange rate on 01/01/1999, which is the 3.592419. Later only you found out that you forgot to maintain the exchange rate but the invoice already posted. So, you can update the exchange rate accordingly and then run the Adjust Exchanges Rates function. Navision will adjust back the value for you by adding additional adjustment line to the detailed customer ledger entries.