You should use their one time payment cards to be safe

Payment processing gateways can see what type of card you're using and many one-time/prepaid cards will be rejected for recurring service or deposit related billing.

Many if not most merchants I deal with refuse those. Which is terribly annoying when it's a shop with clunky checkout flow.

I'm baffled by the fact that the system is designed in any way to enable merchants to know that the card you're paying with is a single use card.

They run two transactions, the first being £0 and it resets the card number causing the second to fail.

That sounds like a bug on Revolut's side. It's supposed to be one payment per number, right?

No, it’s strategic. Feature not a bug. As someone who has integrated with Visa/MC/Amex using old school SOAP APIs, you will get higher quality context about what’s going on with the card when you hit it with a zero dollar transaction. Can’t say for sure if they are doing it primarily to avoid supporting this virtual card thing. But I found it conventional in my fintech stint

Parent is saying Revolut should handle both the 0 payment and the subsequent real payment without resetting the number so that this workflow succeeds. They’re not saying to fix the double charge attempt, which as you say gives more information.

They're saying £0 isn't a payment and Revolut should ignore it. It's not a Revolut bug but it's missed functionality for sure.

I'm not sure, the merchant is running a dummy payment transaction presumably for this scenario so they can avoid people not giving them a card to charge at will.

This is where the card numbers that you can generate are best because you can delete the card afterwards.

This is simply not true. You're not talking about the same type of card. Tell me one website that doesn't allow Revolut one-time virtual cards (note that these are not prepaid cards)

I have Revolut and have encountered this a number of times.

The flow is usually that the merchant runs a check against the card by doing a £0 transaction rather than the correct card active check which resets the card number and causes the second transaction of the correct amount to fail.