How roaming works and how to avoid bill shock

Your mobile operator only has masts in its own country. When you travel, your phone connects to the network of a foreign operator that your provider has a roaming agreement with. That foreign operator serves you and then charges your provider a wholesale rate for the data, calls and texts you've used. Your provider then passes that cost on to you according to your tariff.

So the price of roaming depends on two things: what the foreign network charges your provider, and what your provider decides to charge you. Within the EU, both are regulated. Outside it, neither is.

Since June 2017, the EU's roam like at home regulation has required EU operators to charge the same for using your phone in another European Economic Area country as they would at home. The rules were extended in 2022 until 2032 and cover the 27 EU member states plus Iceland, Liechtenstein and Norway. If you have a SIM from a European operator and you're travelling within that area, you usually don't need anything else.

It does have limits worth knowing about:

• Fair use. The rules are designed for trips, not for living abroad. If you spend more time abroad than at home over a long period, your operator may add surcharges. On tariffs with large data allowances, or no data cap at home, the operator can also set a roaming data limit, and charge a regulated surcharge beyond it.
• The UK isn't included. Since Brexit, EU roaming rules no longer apply there. Some operators still include it as a commercial choice; others charge a daily fee. Check before you go, or see the options for the United Kingdom.
• Nor is Switzerland. Despite being in the middle of Europe, it's outside the EEA and the regulation. The same applies to Andorra and Monaco. If you're heading to Switzerland, check your provider's terms.
• Cruise ships and planes aren't covered. At sea and in the air, phones connect to satellite-based networks that aren't European land networks and can be very expensive. Use Airplane mode or turn mobile data off.
• Watch out near borders. Close to a non-EU border (around Lake Geneva, say, or on Spain's southern coast facing Morocco), your phone can latch onto a non-EU network without you ever leaving the country.

Outside the EU there are no regulated caps. Each operator negotiates its own wholesale agreements, and what it pays the foreign network is usually much higher. Many providers offer daily or per-trip bundles, but these tend to include little data and kick in automatically as soon as your phone connects, even if all it does is download an app update in the background. Popular destinations such as the United States, Morocco, Turkey and Japan are usually outside standard tariffs.

A travel eSIM is a prepaid data plan for your destination that installs on your phone without removing your SIM card. You pay upfront for an amount of data or a number of days, you know the cost from the outset and there are no surprises when you get home. Your usual SIM stays in the phone for calls and texts, while the eSIM handles your data. It's especially worth it when:

• You're travelling outside the EU, including the UK and Switzerland.
• You're visiting from outside Europe, so roam like at home doesn't apply to your SIM. If you're touring several countries, take a look at our roundup of eSIMs for Europe.
• Your tariff has a small roaming data limit and you'll be using a lot of data.

Buying a physical SIM at your destination is another option. It can make sense for long stays or if you need a local number. On the other hand, you have to find a shop when you arrive, register the SIM with your passport in many countries and swap out your usual SIM (with the risk of losing it). A travel eSIM is bought and installed before you leave and works as soon as you land, with no card swapping. Bear in mind that our eSIMs are data-only: they don't come with a local number.

• Turn off data roaming on your home SIM before leaving the EU. This is the single most important setting.
• If you're using a travel eSIM, keep it as your data line, turn on roaming for it and switch off automatic data switching between lines.
• Be careful with Wi-Fi calling. Depending on your provider, a Wi-Fi call from abroad may be billed as a domestic call, as roaming, or may not work at all. And if the Wi-Fi drops, the phone may switch to the foreign mobile network. Check with your provider.
• Incoming calls can cost money too outside the EU. If you're not expecting any, divert to voicemail or use messaging apps.
• Read your provider's alerts. EU operators must text you their terms when you arrive in another country and apply a default spending limit on data roaming, with a warning before you reach it. You can change it, but think twice before switching it off.

Will I pay roaming charges in the UK with an EU SIM?

It depends on your provider. Since Brexit, EU rules don't apply there and each company sets its own terms.

Does roam like at home include Switzerland?

No. Switzerland is outside the EEA and the regulation, although some operators include it voluntarily.

What happens if I use my phone on a cruise?

At sea, phones use satellite networks that aren't covered by EU rules and can be very expensive. Switch on Airplane mode.

Do I need a travel eSIM for trips within the EU?

If you have a European SIM, usually not. It can be worthwhile if your roaming data limit is small or your SIM is from outside Europe.

Can I still receive calls with a travel eSIM?

Yes. Your usual SIM stays in the phone for calls and texts; just turn off its data roaming.

Why do I need to turn on roaming for the travel eSIM?

Because the eSIM connects to partner networks at your destination. Without roaming enabled on that line, it won't get online.