Multi-currency affects many accounts and balances in your company file.
Once you turn the Multi-currency feature on, you cannot turn it off again, so be absolutely sure you want to turn it on.
You can assign a currency to most types of accounts, including customers, vendors, bank and credit card accounts, accounts receivable, and accounts payable.
Income and expense accounts always use your Home currency.
Your Home currency is the currency of the country where your business is physically located.
You can only assign one currency to each account or contact name, and you have to add a new account for each different currency that you will use in transactions.
After you turn Multi-currency on, new fields appear on some screens:
Once an account has had a transaction posted to it, you can no longer change the account's currency,
See the following articles for more information about the Multi-currency feature