The terminals in Portugal definitely show a DCC prompt but the implementation is very tricky. The experience feels designed by the merchant banks to get you to inadvertently go for DCC. I would ALWAYS have them place the reader down on the table in front of you before tapping and keeping it until a receipt has been printed.

The implementation in Portugal (both at merchants and at ATMs) seems to be:

1. Ask if you want to be charged in USD (1) or Euros (2).
2. It then asks again using completely different verbiage: ACCEPT CONVERSION (1) OR REJECT CONVERSION (2).

The 2nd prompt is what may catch you out, because if you don't read it properly, you might assume it's asking you to continue the transaction, but it's NOT, it's still the DCC. Also, if you hand the terminal back to the merchant after just the first prompt, then they can then still (inadvertently or purposely) DCC you.

My experience with this has been that tourist spots have "mistakenly" DCCed me more than others, which make it seem less like a mistake as one would assume they're more familiar with foreign cards than the local establishments where it doesn't happen. In one scenario, a merchant literally saw me hit EUR and I told him EUR please and then he grabbed the machine before the second prompt and out popped a receipt with DCC on it.

And the setup you described is unlikely compliant with Visa/MC DCC implementation rules. I have seen the "are you sure?" prompt in the past on an ATM, but I forget where that was.

At least this is unlike some implementations in China where there is no DCC prompt at all. The terminal just DCCs you.

I know you used quotes around mistakenly, but I wouldn't give any merchants the benefits of the doubt when it comes to DCC. I hope in the above situation you either had the merchant void and rerun the transaction without DCC or promptly disputed the amount.

In the future, I am likely to file complaints with Visa or MC, depending on which card I use, since it appears that they've been following up on merchant complaints with surcharging. I imagine that they might follow up with a DCC complaint as well.

Thanks for the reminder about this. Just checked my Hong Kong hotel bill, and it was not back-office manipulated. (Although last time I was in China, the back office did manipulate and I successfully disputed.)

Congratulations on the successful dispute.

Back office DCC from hotels is usually less of a problem outside of the US and Canada since the checkout process is more active in the sense that one often goes down to the front desk to settle the bill and release the hold that the reception placed on the card on file at check in. In the US and Canada, especially at limited service properties, it's possible to bypass the front desk completely with an app-based check in. When checking out, it's often possible to use the app, at least for Marriott, Hilton, and Hyatt, after confirming the e-mail version of the bill.

Outside of the US and Canada, I always stop by the desk as a best practice to close out the bill.

Yes, that is was I did and my bill was charged in RMD and zeroed-out. When I got back, it all of a sudden was charged in dollars, which resulted in a $60 extra expense. I disputed that and Chase ended up refunding the entire hotel bill (when the hotel did not respond to them), saying that I could not just dispute the $60 extra.

Scotiabank ATM in Oaxaca, MX, offers conversion from Mexican Pesos to US Dollars for a convenience fee of a mere 14%. No, thanks.

Chase will just automatically resolve with a credit adjustment:

"We resolved your dispute.Checkmark We resolved your dispute.
We credited your account for $1.00, which you'll see on your next statement."

It depends on the amount of the dispute. While I understand it's not worth it for the card issuer to go the full chargeback route, it won't change the merchant's bad behavior by issuing a courtesy credit.

At any rate, I'm happy that you aren't out any money personally.

Related question, not quite DCC but this seems like the crowd that would know. Hypothetical: Hotel in Mexico quotes $50 USD for an upgrade. The bill is in pesos, so the hotel picks a terrible conversion rate on the bill, 20% wrong, say. Would a credit card dispute yield any help (quoted $50, but charged $60 is the logic)?

I would insist on the hotel quoting prices in pesos. Then, try to pay via Amex. If they don�t accept it, then make sure you choose pesos if a choice of a currency is given.

I have only stayed in a few hotels in Mexico, but two Hilton properties, one in Cancun and one in Puerto Vallarta, billed in USD natively without DCC. Some things were priced in MXN, but the hotel ran my card in USD at the point of sale. There was a conversion to MXN that seemed in line with the exchange rate. I don't know if non-local cards are billed in USD as well and only local cards would use MXN. A third hotel billed in MXN.

In the situation you described, you'd have little recourse if the transaction occurred in MXN, but my guess is that the above property might be like those two Hiltons and use USD as the currency denomination.

Inserting the card could alternatively result in signing using your PIN code before you see the receipt. The only safe method is to film the whole transaction and use the film as evidence.

If you tap your card and don't sign anything, how would the merchant prove that you have consented to using DCC if disputed?

Given that fact that the OP user profile posts a location in LA, my reasonable assumption is that the card the OP would use is likely to be a chip-and-signature card. You are correct that there's little recourse for terminals that (improperly) force DCC after a PIN entry.

In the tapped payment scenario, it's just as easy to ask how would you prove that you opted out of DCC?

What should - but probably won't - happen is to require merchants offering DCC to provide a quote slip, which was/is common in some Southeast Asian locations, or a currency selection on the final receipt, which is common in Hong Kong. That would show customer intent for any currency selection and be a valid piece of evidence you could provide to your card issuer if the merchant subsequently forced DCC.

I've long been curious about what percentage of customers really accept DCC, and finally found a scholarly article today indicating that in some cases it's around 50%. In some ways it's surprising to me that it's taken so long for social scientists to run an experiment on who is most likely to accept DCC (spoiler: it correlates with financial literacy) - it seems like it could be a fun dissertation topic for someone studying economic sociology or psychology...

Financial literacy no doubt plays a role about knowledge of DCC, but even knowing it exists doesn’t mean that users always see the prompt.

With the advent of mobile POS and contactless in Europe, and the fact that the tap point is at the top of the machine, many users are not aware the option even showed up, especially because it doesn’t show up always at every merchant. I sometimes feel like a jerk asking to hold onto a machine from a store clerk, only for the DCC prompt to not even appear in that situation, but they’re often too fast to hit Accept if you don’t.

Placing that burden on users is bad, but unfortunately I don’t think there’s any incentive for anyone to enforce better flows. The networks and banks make a ton of money on foreign transactions, and most transactions, especially in Europe don’t see the prompt given the shared Euro currency so it’s not a priority.