Before you start

An unlocked handset, or one that supports eSIM
A Belfast address, for a contract or broadband
A UK bank account, for a contract Direct Debit

Step-by-step

1
Buy a pay-as-you-go SIM or activate an eSIM on arrival
Sold in supermarkets, phone shops and online with no identity registration at all. A UK number in your first hour unlocks bank verification, HSC appointment systems and delivery notifications, all of which assume you have one.
In personWho: YouDay 1
2
Do not attempt a 24-month contract in your first weeks
Contracts run a credit check and require a UK bank account and address. With no UK credit file you will be declined or asked for a deposit. Rolling one-month SIM-only plans have no credit check and are excellent value.
OnlineWho: You
3
Check your plan's Ireland roaming before you go anywhere near the border
Irish masts reach well into Northern Ireland and phones latch onto them without being told to — on the Enterprise to Dublin, along the Newry road, and in parts of south Armagh and Fermanagh. Post-Brexit some UK operators reintroduced EU roaming charges and some did not. Check what yours does in the Republic, and turn off automatic network selection if it is expensive.
Mobile appWho: You
4
Order broadband the day you have an address
Installation takes one to three weeks and may need an engineer visit. The good news is unusual: Ofcom's 2025 figures put full-fibre availability in Northern Ireland at 95% of homes, the highest of the four UK nations by a wide margin — against 79% in England, 78% in Wales and 71% in Scotland. In most of Belfast the question is which fibre provider, not whether.
OnlineWho: You
5
Keep your number when you switch
Text PAC to 65075 and you receive a porting authorisation code by return, valid for 30 days. Ofcom rules require the switch to complete in one working day. Never cancel the old service first — that is how people lose the number.
Mobile appWho: You
6
Take a SIM-only plan and buy the handset separately
A rolling SIM-only plan with a large data allowance costs a fraction of a bundled handset contract over the same period and can be switched monthly. Buying the phone outright is almost always cheaper in total.
OnlineWho: You

Documents you’ll need

Nothing at all for pay-as-you-go
A Belfast address and bank details, for a contract
Passport, occasionally requested for a contract

Things most newcomers don’t know

Northern Ireland has the best full-fibre coverage in the UK, by a distance.

Ofcom's 2025 Connected Nations figures put full fibre at 95% of Northern Irish homes against 79% in England, 78% in Wales and 71% in Scotland, with 96% able to get a gigabit connection. For remote work that inverts the usual UK story, where fibre is the exception outside new-build. In Belfast you are choosing between fibre providers rather than hoping for one.

Source: Ofcom — Northern Ireland leads the way on full fibre connectivity

Your phone will roam onto an Irish network without asking you.

This is the only part of the UK with a land border, and coverage does not respect it. People pick up roaming charges on a day trip, on the Dublin train, or simply sitting in a border-county kitchen. Check your operator's Republic of Ireland terms, because post-Brexit they differ sharply between networks.

Source: Ofcom — coverage and speeds

The UK has no SIM registration, unlike Ireland and most of Europe.

Ireland introduced mandatory SIM registration and Germany, Spain and France all require identity verification. The UK requires nothing for pay-as-you-go, so a working UK number is a fifteen-minute errand — and a working Irish number, if you need one for cross-border work, is not.

Source: Ofcom

Text PAC to 65075 — switching keeps your number in one working day.

Ofcom requires networks to issue a porting authorisation code by text on request and complete the switch within one working day. Most people never learn the shortcode and stay on an expired contract tariff for years.

Source: Ofcom — switching mobile provider

Common mistakes to avoid

Signing a 24-month handset contract in your first weeks and being declined or asked for a deposit.
Picking up Irish roaming charges on the train to Dublin without checking your plan.
Cancelling the old service before requesting a PAC code, and losing the number.
Assuming Belfast broadband is as patchy as an English Victorian terrace — it usually is not.
Not knowing that pay-as-you-go requires no identity check at all.

Some of this may be out of date. Spotted something inaccurate? Help us keep it right for the next newcomer.