Purchases and cash withdrawals you make abroad are debited in euros either to your bank account (debit) or credit facility (credit).
When you make a purchase or withdraw cash in a currency other than the euro, the wholesale rate of the currency used in either the Mastercard Europe or Visa International system (depending on the card) is applied. A currency adjustment (2.25% of the transaction amount at the most) is added to the wholesale rate.
The wholesale rate is determined according to the date on which the transaction is transmitted to Mastercard Europe or Visa International. The exchange rate used for a card transaction is given in the transaction details on the account statement of the account linked to the card or on the credit card invoice.
You can view indicative exchange rates on the international pages of Mastercard and Visa.