Paying with your phone abroad: does Apple Pay or Google Wallet need data?

At the till, the payment does not travel over your data

A contactless payment with your phone is a short-range exchange between the phone and the card reader, using NFC. The reader then sends the payment through the shop's own network. Card issuers say this plainly in their help pages: you can pay in a store without a network connection, but you need one to pay in apps and online.

Apple adds a detail that matters on the road: when you use Apple Pay, the number transmitted to the merchant is a device account number, not the number printed on your card. In Wallet you can see its last four digits on the card's details screen, which helps if a receipt shows digits you do not recognise.

In practice, this means you can step off a plane with no signal and still pay for the train into town at a contactless barrier, or for a coffee at the airport.

Five things to have ready before you fly

• The card already added to Apple Wallet or Google Wallet. Adding one means your bank has to check it, so do it at home, with a connection and time to spare.
• A card your bank allows: Google says its bank decides whether its cards work with Google Wallet, and Apple Pay takes cards from participating banks in the countries where it is available.
• On Android: NFC switched on, a screen lock set up and Google Wallet chosen as the default payment app. Google lists all three as requirements.
• A charged phone. A wallet with no battery is no wallet.
• A physical card in your bag, for terminals that do not take mobile payments.

Apple says Apple Pay is accepted wherever you see the contactless symbols, and Google says the same for its contactless or Google Pay marks.

Where you do need a connection

Buying a museum ticket on a website, paying for a ride in an app or booking a hotel on your phone are online payments, and those go through the internet. Many of them also ask for strong customer authentication: a confirmation in your bank's app or a code by text. The app needs data; the text goes to your phone number, not to a data line. Our guides on getting bank SMS codes abroad and on two-factor authentication while travelling explain how to keep both working.

The other thing that needs a connection is your bank talking to you: payment notifications, a fraud check that asks you to confirm a purchase, or a card you need to unlock in the app. A data-only eSIM such as Snoozim's covers that part while your usual line stays available for texts.

Paying with a watch, and when the battery is low

On an Apple Watch, Apple's steps are to double-click the side button, let the default card open and hold the display near the reader until you feel a tap. Google notes that paying with a smartwatch also depends on your location, as you have to be in a country or region where that feature is supported.

Express Mode is a separate case. It lets some transit cards and payment cards set for transit work without waking or unlocking the iPhone, and Apple says power reserve keeps some of these Express Mode cards working for up to five hours when the iPhone needs charging. It does not apply if you switch the phone off yourself, and it is meant for transit gates, not for every payment. The ordinary payment at a shop till still needs a phone with battery.

When the terminal asks which currency to use

Outside your own currency, some terminals and cash machines offer to charge you in your home currency instead of the local one. That is a currency conversion, and its cost depends on who does it. The EU's consumer rules say that your card provider, your bank, the trader or the website carrying out the transaction must tell you the amount of any currency conversion fee before you agree to the purchase.

The same rules require banks to charge the same for a payment in euros across the EU as for an equivalent payment at home. What your own card charges outside that case is in its terms and conditions, so the person to ask is your bank, before the trip rather than at the till.

If the payment does not go through

Google's troubleshooting list is a good order to follow on any phone: hold the phone against the reader a few seconds longer, look for the NFC symbol on the terminal, make sure the phone is unlocked, open the wallet app before you pay, try another reader, and confirm the shop accepts mobile payments. If it still fails, contact your bank or use a different payment method.

If the phone itself is lost, putting it in Lost Mode with Find My suspends the cards you use with Apple Pay. Our lost or stolen phone guide has the full order of steps.