Definition
Dynamic currency conversion (DCC) is a payment technology that, when you pay by credit card abroad, instantly converts the bill into your card's home currency (for Korean cards, Korean won) instead of charging the local currency. Seeing the amount in your own currency at checkout looks convenient. But the intermediary payment processor adds a poor exchange rate and extra fees, so you end up paying more.
The "Double Conversion" Trap Hiding Behind a Friendly Screen
When you travel abroad, the card reader often asks you to pick between something like "USD" and "KRW" (Korean won). Choosing your home currency feels reassuring because the price looks familiar. But it's actually a shortcut to paying a high fee.
When a foreign terminal processes a payment in won, the local payment network applies its own high exchange rate. On top of that, it adds a conversion fee of 3-8%. Technically, this is called dynamic currency conversion (DCC).
And the trouble doesn't stop there. A Korean card company can't process an amount billed in won overseas directly. The charge goes through an international card network (Visa, Mastercard, and so on), where it goes through a double conversion: "won to dollars, then dollars back to won." You end up paying conversion fees twice, a few percent more than if you had paid in the local currency.
A Bit More Precisely: What Happens on the Financial Network
In the one or two seconds it takes to swipe your card, a complex exchange of messages takes place between the payment terminal (POS) and the servers of the payment processor (VAN/PG). The terminal reads the first digits of the card number (the BIN) and immediately figures out that the card was issued in Korea.
Once the system knows the country, it automatically runs a currency conversion calculation and shows a screen that says, "In your country's money, that's this much." This feature was originally developed as a convenience for tourists, to show them a fixed amount with no exchange-rate risk.
Today, however, it has turned into a business model in which local merchants and payment processors share the fee revenue. If you choose your home currency, the processor's own rate and fees, which are unfavorable to you, apply instead of the standard exchange rate.
The Surest Way to Avoid the Rip-Off Fee
When a card terminal abroad shows a currency choice screen, always choose the local currency (dollars, yen, euros, and so on). When you shop on overseas websites or use hotel booking apps, it's also safest to keep the payment currency set to the local currency or US dollars (USD).
To guard against mistakes, sign up for your card company's overseas won-payment block service in its app before you leave Korea. With this service on, the card company automatically declines any payment request made in won, which shuts out DCC fees at the source.
If your receipt shows an amount in "KRW" instead of the local currency, ask the clerk right away to cancel the authorization and charge you again in the local currency. Once the payment is completed and approved, it is very hard to get the fee back.
Common misconceptions
Paying in Korean won (KRW) abroad is a better deal because you don't have to work out the exchange rate.
Paying in won adds a won-payment fee (about 3-8%) and triggers two conversions, so it actually costs more.
Since the card was issued in Korea, paying in won abroad is the default.
The default in international payments is the local currency. Won payment is an add-on service that intermediaries offer to earn extra fees.
Where you meet it
You're checking out at a hotel front desk abroad, and the card terminal screen asks you to choose between won (KRW) and the local currency.
You set the currency to won when booking a flight on an overseas website, and your card statement shows a bigger amount than you expected.
In one sentence
Choosing won when paying abroad adds an unfavorable exchange rate and double fees, so always pay in the local currency.