debit cards, as the authorization holds can expire before the transaction is settled. Additionally, some agencies use the requirement of a credit card as a tool to screen high-risk customers, as credit cards usually require a good credit history, and all that is needed for a debit card is a checking account. Another example of a transaction that may settle for an amount different from the amount authorized is a transaction incurred in a currency different from the currency in which the card is denominated. The final, settled, transaction amount will be based on the exchange rate in effect on the settlement date. Since that rate is generally not known at the time of authorization, the banks will use an estimated amount based on the exchange rate at the time of authorization. References External links Visa International Operating Regulations Banking terms