If you don't have enough money in the right currency for the card payment you're attempting, but you do have enough money in another currency which allows alignments, money will be taken from the currency you have sufficient funds in, and exchanged into the currency you are making the payment in.
For example, if you are trying to make a €20 euro transaction and have a 0 balance in euros on your account, but you do have $100 USD, the money will be exchanged and taken from your pot of USD funds in order to complete the payment and allow the card to pay the merchant in the currency requested. This is called alignment.
Please note alignment is not possible in every one of the 20 card currencies. Currency alignment will not take place for transactions in the following currencies: Czech koruna, Romanian new leu, Turkish lira, Israeli new shekels, and Singapore dollars. If you attempt a transaction in any of these currencies and do not hold enough of that currency to complete it, the transaction will decline.
