Many of us have already heard of — or painfully experienced — foreign transaction fees.

It happens almost always after we return home when we get our credit card statements. A foreign transaction fee is for anything you purchased abroad — ranging from 1% to 3% of your total purchase.

And the confusion often happens when foreign merchants offer you the convenience of charging you in dollars instead of the local currency.

This is especially true on cruise ships, where all transactions are done in U.S. dollars. But the ship isn’t registered in the U.S., and all of its financial dealings are routed through banks overseas.

What’s the key to avoiding those foreign transaction fees? Don’t just check where the travel provider is based, or where you departed from, but where the travel provider does its banking.