Foreign transaction fees on cards tapped for Tube?

Each journey is not individually charged. The system tracks the taps then charges the card used only one time in the early morning of the next day.

There's only a single charge for a card with a foreign transaction fee.

Helpful, thank you

Could you add one of the 3 no fee cards to a phone and have the fourth person tap in and out with phone?

Is that considered a different form of payment?

Jean I'm not sure. It would certainly be handy if so.

I think you can avoid all of this by purchasing a Travelcard (doesn't have a fee like Oyster). Or by setting up an account on the TfL app. Or both?
https://tfl.gov.uk/fares/how-to-pay-and-where-to-buy-tickets-and-oyster/travelcards-and-group-tickets

If you and your wife have a joint credit card where you each have your own card with the same account number, you can both tap your cards on the same train.

Most cards that charge a foreign transaction fee charge a percentage of the amount charged. So whether you are charged after each transaction or just once at the end of the day, it’s all the same. If you are charged a per transaction flat fee, then that would be different.

Does your card charge a flat fee per transaction or a percentage?

My credit card with a foreign transaction fee (FTF) charges 3%. I think that is pretty typical of cards with an FTF. The daily cap for zone 1-2 is 8.90 GBP. If a person with a card with an FTF hit the cap, they’d be paying an extra 27p a day (about 37 cents U.S.). I don’t think that is much to worry about.

Ah, so percentage of a daily fare isn't much.

Without getting too into the weeds, my daughter's friend, who is traveling with us might be working with a debit card, which I know sometimes have set fees. I'll check with her which card she is bringing.

My wife and I do have duplicates of the same fee free cards (Chase Sapphire Reserve and Amex Platinum) so we could cover the group with those. Which I suppose would involve trusting teenage girls in a great shopping city with some really high credit limits ;)

the uniqueness of the payment is composed of both the account on the card and the method of payment. So if the card is put on a couple of phones and a watch or fitbit, one can use the card, one the watch or fitbit and the couple of phones.

Nigel, thanks for confirming.

Thanks Nigel

You can add one card to multiple phone pay apps. Apple Pay / Google Pay generates a pseudo card number unique to that phone. This is passed to TfL rather than the actual card number when you tap, so it sees them as separate payment devices. Just make sure to tap with the same phone or card each time to preserve the fare capping.

ck99 thanks for the definitive answer :)