The most predictable administrative failure of emigration: the identity checks that let you into HMRC's services assume you still hold a UK mobile number and a UK credit footprint. Losing both at once locks people out for months.
Nothing about this is a tax rule, and it causes more grief than most of them. HMRC's online services sit behind a Government Gateway account, and access to that account depends on identity verification methods designed around people who live in the UK: a mobile number that receives a text, an authenticator app tied to a device you still have, and knowledge-based questions drawn from a UK credit file that stops updating once you leave.
Cancel the UK SIM, change phones, and lose the passport that was your fallback document, and you can find yourself unable to file a return you are legally obliged to file. HMRC does have routes back in, but they are slow, and the deadline does not move while you use them.
Do These Before You Leave
- Keep one UK mobile number alive. A cheap pay-as-you-go SIM kept in credit is the single most effective piece of emigration admin there is. Roaming or a UK eSIM both work.
- Set up an authenticator app as a second factor and make sure you know how to move it to a new phone. App-based codes are not tied to a network.
- Record your Gateway user ID somewhere durable — not in a browser you are about to abandon, and not only in a UK email account you may stop using.
- Update your address with HMRC to the overseas one. Correspondence going to your old UK address is how most penalty problems begin.
- Print or export what you will need: recent tax calculations, your National Insurance record, your State Pension forecast.
Do not cancel the UK number as part of the move. It is the cheapest insurance in the whole process, and it also keeps you reachable for banks, brokers and pension providers who apply the same assumptions — see keeping a UK bank account.
If You Are Already Locked Out
| Problem | Usual route back |
|---|---|
| Lost the phone that receives codes | Recovery via the alternative factor you registered, if you registered one |
| Cancelled the UK SIM | New UK number, or switch the account to an app-based factor |
| Identity questions you cannot answer | Alternative document routes, then contact by phone or post |
| Forgotten user ID | Recovery to the registered email; keep that email alive |
| Everything at once | Contact HMRC directly and allow weeks, or appoint an agent |
Where the account cannot be recovered in time, appointing an agent is the practical answer. An accountant with agent authorisation can file on your behalf through their own software, which also solves the separate problem that HMRC's free service will not accept the SA109 residence pages anyway.
What You Lose Access To
- Self Assessment — filing, viewing calculations, and checking what HMRC thinks you owe.
- Your National Insurance record, which matters if you are considering voluntary contributions from abroad.
- Your State Pension forecast, the document behind most decisions about filling gaps.
- PAYE information from your final UK employment, including the figures behind a refund claim.
The NI record and forecast are the ones people miss most, because the decision to buy voluntary contributions is time-limited and hard to make blind. Our guide to voluntary NI from abroad explains what that decision involves.
Post Still Works, Slowly
HMRC remains reachable by post and by phone from overseas, and for genuinely stuck cases that is the route. Build in weeks. If a filing deadline is approaching and access is not restored, file on paper or through an agent rather than letting the deadline pass on the theory that being locked out is a reasonable excuse — it sometimes is, and it is not a position you want to be arguing from.
Frequently Asked Questions
Should I keep a UK mobile number after I move abroad?
Yes. It is the cheapest and most effective thing you can do. A pay-as-you-go SIM kept topped up preserves access to HMRC, banks, brokers and pension providers, all of which assume a UK number.
Can I still file if I cannot get into my Government Gateway account?
Yes, by paper or through an agent. Neither route depends on your online access, and an agent can also file the residence pages that HMRC's own free service does not support.
Will HMRC accept being locked out as an excuse for filing late?
Sometimes, on reasonable-excuse grounds, but it is not something to rely on. The safer approach is to use a paper return or an agent rather than to let the deadline pass while recovery is in progress.
Does HMRC send anything to my overseas address?
It will, if you have told it your overseas address. If you have not, correspondence keeps going to your last UK address, which is how most penalty spirals start.
Related Guides
Keep reading with these related guides and calculators:
- SA109 — why the free service will not file it anyway
- When to stop filing — the obligation behind the access problem
- UK bank accounts abroad — the same verification problem, elsewhere
- Voluntary NI abroad — the record you need access to see
- Paying HMRC from abroad — settling up once you are back in
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