A handful of money mistakes account for most of the avoidable cost on an international trip: paying foreign transaction fees on a card that could have avoided them, accepting dynamic currency conversion at the point of sale, misjudging which currency is actually being quoted, and letting a bank’s own fraud system freeze a card mid-trip. All four are avoidable with checks that take minutes, done before departure rather than after a statement or a declined transaction ruins an afternoon.

Tell your bank before you fly, not after a card gets declined

The single most common money problem abroad has nothing to do with theft or exchange rates. It is a card that stops working because a bank’s own fraud system flagged an unusual overseas transaction and froze the account. It is entirely avoidable: tell every card issuer travel dates and destinations before leaving, not just for a primary card but for a backup one too, since an unregistered backup card is not actually a backup. While doing that, check each card’s foreign transaction fee and each bank’s ATM fee policy directly, since not every card charges one and the ones that do rarely advertise the percentage clearly at the point of use.

Decline “pay in your home currency”

When a card terminal or ATM abroad offers to convert a charge into a home currency on the spot, known as dynamic currency conversion, the exchange rate applied is almost always worse than a card issuer’s own rate. Paying in the local currency instead is usually the cheaper option, and this applies whether the offer comes from a restaurant terminal, a hotel front desk or an ATM screen.

What to actually carry

There is no single right ratio of cash to card, since it depends on the destination, but the underlying logic holds everywhere: cards for most spending, since a lost card can be frozen while lost cash cannot, plus a modest amount of local cash on arrival for taxis and small vendors before locating a reliable ATM, and a separate emergency reserve kept apart from an everyday wallet for the scenario where a card is lost or frozen entirely. Where ATM access is not reliable or widespread, that shifts the calculation toward carrying more cash and relying less on card transactions, which is worth checking specifically for the destination rather than assuming it works the way it does at home.

Using ATMs abroad safely

A few habits do most of the work: use machines attached to a bank branch where practical rather than a freestanding one in a tourist area, which is both more likely to carry a card skimmer and more likely to charge a steep flat fee; cover the keypad when entering a PIN regardless of how safe the location feels; and decline the ATM’s own currency-conversion offer for the same reason a card terminal’s version should be declined.

Know which currency is actually being quoted

In parts of the Riviera Maya, prices are commonly quoted in US dollars even though the local currency is the Mexican peso, a detail that changes what “cash on hand” should actually mean for a trip to that region. The pattern is not unique to Mexico’s Caribbean coast: resort areas across the wider Caribbean commonly quote in US dollars alongside a local currency, and some, like the Bahamas, peg their own currency to the dollar at a fixed rate specifically because of how much of the local economy is dollar-facing. That does not mean a card or cash in the local currency is unnecessary; it means checking which currency a specific receipt, rate or tip request is actually denominated in, rather than assuming the number on the page is automatically in the currency in your wallet. Multi-country Europe trips carry their own version of the same problem across eurozone and non-eurozone countries; our eurozone currency basics guide covers that case specifically.

If something goes wrong anyway

Know a bank’s international support number in advance, since the domestic one may not work from abroad or may be expensive to call. Arrange, before leaving, for someone at home who can access funds on your behalf if genuinely stuck, rather than improvising that arrangement over an international call. A US embassy or consulate can help in a genuine emergency, though this is not a routine backup plan and exists specifically for travellers left unexpectedly without funds through unforeseen circumstances.

The full breakdown of cards, ATMs and cash strategy for any international trip is in our money abroad guide, and tipping practice at all-inclusive resorts specifically is covered in our tipping and etiquette guide.