DCC (Dynamic Currency Conversion) = when you pay abroad in your home currency, the merchant's side converts for you and pads the rate by 3%โ7% (sometimes more). It's sold as "convenience" but quietly costs you.
How does DCC happen?
Precondition: you're abroad and the local currency โ your card's settlement currency. Example: you're in France, the price is โฌ100, and your card settles in CNY. Since EUR โ CNY, the terminal (which reads your card as a CNY card) offers: "pay in EUR (local) or CNY (your currency)?" โ your choice decides who converts:
You pick
Who converts
Currency sent to network
Result
EUR (local) โ
Your card network converts near mid-market
EUR
Cheaper
CNY (DCC) โ ๏ธ
Merchant converts on the spot, +3%โ7%
Already CNY
Overpay
Don't reverse the causality: "transaction currency ends up = card currency" is the result (symptom) of DCC, not the cause. The cause is being abroad (local โ card currency) AND choosing home currency. So if a foreign purchase posts directly in your home currency (instead of local currency converted by your bank), you were most likely DCC'd.
What it looks like
At the terminal or checkout, you see: "Pay in CNY (your currency) or local currency?" with a helpful "1 EUR = 8.1 CNY" rate. That rate is usually the marked-up DCC rate. Just choose local currency to avoid it.
How to tell if you were DCC'd
Check the statement: if a foreign purchase posts directly in your home currency (not the local one), it was likely DCC. Compare the price, the amount charged and that day's mid-market rate โ if your effective rate is more than ~3% above mid-market, it's almost certainly DCC.
Check it instantly: use CardAbroad's receipt checker โ enter the price, the amount charged and the mid-market rate to see the markup % and how much extra you paid.