How to Receive Bank OTP Codes While You Are Abroad

A one-time passcode is sent as an SMS to a phone number, and that number is your home one. It has nothing to do with which plan is carrying your data, so buying a travel eSIM does not move your passcodes onto it and cannot. The question is therefore narrower than it looks: what has to remain true about your home line for an SMS to reach it while you are in another country.

The short answer is that the SIM has to be present in a phone that is switched on and registered to some network. Incoming SMS is almost always free to receive while roaming, and on most phones it does not require mobile data to be enabled on that line at all.

Three things, and only the first is non-negotiable:

1. 1The home line is active and registered. The physical SIM or eSIM profile is in the phone, the line is enabled, and it has found a network. Airplane mode with no exceptions breaks this; so does removing the SIM to make room for a travel one.
2. 2Voice roaming is permitted on that line. SMS rides the signalling channel that voice uses, so a line barred from roaming entirely will not receive one.
3. 3Data roaming — optional, and usually the thing to leave off. Text SMS does not need it. This is the setting that produces surprise bills, and switching it off does not stop passcodes arriving.

That third line is the one worth internalising, because the common advice to "turn off roaming" is ambiguous and people apply it to the wrong switch. Data roaming off, line on, is the setup you want.

The reason eSIMs made this easier is that they removed the trade-off. A dual-SIM phone runs your home line and a travel plan at the same time, so you no longer choose between receiving your bank codes and having affordable data. Apple documents the mechanics of using Dual SIM on iPhone, and Google documents the same arrangement for dual SIMs on a Pixel phone — pick which line handles calls, texts and data, and the phone uses it automatically.

The configuration that works:

• Home line: on, data roaming off. It receives calls and SMS, and costs nothing while idle on most tariffs.
• Travel eSIM: on, set as the default line for mobile data.
• Default voice line: your home number, so an outgoing call still shows the number your bank has on file.

Set the data line explicitly rather than trusting the default. A phone that picks the home line for data is the single most expensive misconfiguration in this whole subject, and it is silent until the bill.

In rough order of how often each turns out to be the cause:

• The home SIM was taken out to fit a local one. A physical swap forfeits the number, and with it every passcode. This is the failure an eSIM exists to avoid.
• Call and SMS forwarding was left on. A forwarding rule set months ago quietly diverts the message. Dialling *#21# reports it and ##002# clears every rule — see the guide to USSD and GSM codes.
• The bank blocks foreign delivery, or its SMS provider does. Some institutions genuinely will not send to a roaming line. This one is not fixable from your side and is the reason to check before travelling.
• The passcode is going to an app, not an SMS. Many banks moved to in-app approval, which needs data rather than a signal — and that data can perfectly well come from the travel eSIM.
• Prepaid home line expired. A prepaid number can lapse while you are away, taking the line down with it.

Sometimes the home line genuinely cannot come with you — a lapsed prepaid number, a work phone, a bank that will not send abroad. In that case move the second factor off SMS before you travel rather than trying to rescue it afterwards. It is the direction the standards are pushing anyway: the current revision of NIST’s digital identity guidelines on authentication classes a passcode delivered over the phone network as a restricted authenticator, on the grounds that numbers get reassigned and messages get intercepted.

• An authenticator app generates codes from a shared secret and a clock, so it works with no signal whatsoever — including in airplane mode.
• In-app approval needs only a data connection, which your travel plan already provides.
• A hardware security key needs no network and no battery.
• Backup codes, printed and carried separately from the phone, are the fallback when everything else has failed.

All four have the same advantage over SMS: they do not depend on a foreign network agreeing to deliver a message to a roaming line.

Check the forwarding rules on your home line, confirm the bank will send to it abroad, move what you can to an authenticator app, and leave data roaming off on that line. Then the only remaining decision is where the data comes from — which is the part worth shopping for, because the gap between an airport tariff and a competitive plan is large and entirely avoidable. Compare eSIM plans for your destination before you go, and keep the home number exactly where it is.