A phone can cross a charging boundary without its owner crossing a border. A traveller on a ferry may connect to a satellite network; a phone near a frontier may select a neighbouring country’s network. The destination printed on a ticket is only the first check.

Our comparison of Irish and EU guidance separates three questions: which country is included, which network is connected, and how much of the plan can be used. Keep the answers with the trip details before departure.

Country: check the actual list

The European Commission’s roaming guidance, updated in July 2026, lists the EU, Iceland, Liechtenstein, Norway, Ukraine and Moldova within the current roam-like-at-home area. Ukraine and Moldova joined from 1 January 2026. The UK is outside the compulsory regime, even where an Irish provider voluntarily includes it.

For a Belfast, London or Swiss trip, check the named destination in the provider’s current plan terms. Do not infer inclusion from geography or an old advertisement. Calling another country while at home is also a different activity from using a phone while roaming abroad.

Allowance: unlimited at home is not the whole answer

ComReg’s roaming advice explains that a fair-use data allowance can apply even to a domestic unlimited plan. Check the number of gigabytes included, the period it covers and the charge after it is used. Save the terms for the exact tariff, not just the provider’s general travel page.

As an original planning example, suppose a hypothetical trip allowance is 12 GB and intended use is 2 GB a day for seven days. That is 14 GB, leaving a 2 GB gap. This is a budgeting calculation, not a prediction of an app’s consumption or a quote for any network. Reduce expected use or compare a suitable alternative before buying.

Network: a ferry is a separate charging environment

Both sources distinguish terrestrial roaming from non-terrestrial services on boats and aircraft. A journey between two included countries does not automatically bring a ship’s satellite service within domestic rates.

Read the welcome and charging messages. Where unwanted roaming is a concern, check data-roaming and automatic network-selection settings. Turning off data roaming addresses mobile data; it should not be treated as a universal block on every possible voice, text or Wi-Fi charge.

Keep a three-line trip record

Record destination and inclusion; data allowance and excess rate; and the network or connection type to avoid. With two SIMs or an eSIM, add which line handles data and whether the home line remains active. An eSIM purchase does not itself configure every handset setting.

Keep relevant notifications and usage records if a bill is disputed, then use the provider’s complaint process. Review the record for each trip: country lists, tariffs and allowances can change even when the phone number stays the same.