Last checked: October 2026
The TL;DR
Most people leave the UK by booking a flight and telling their friends. The problem is that HMRC does not know you have gone, and until you tell it properly, you are still on the hook as if you never left.
Leaving properly is a filing, not a feeling. Done right, it stops your foreign income being dragged into UK tax, often triggers a refund for the year you go, and gives you a clean, defensible record if anyone ever asks. Done badly, it creates years of confusion, missed refunds, and awkward questions about which year you actually left.
This guide is the clean-exit checklist: the one form most people need, what changes if you file a tax return, the split-year rule that saves you money, and the short list of everyone else you have to tell before you go.
Covered in this article
1. 🛫 “Left” is a filing, not a feeling
Here is the trap: you can pack up, fly out and start a whole new life abroad, and as far as HMRC is concerned, nothing has happened. Your tax affairs carry on as if you are still a UK resident until you actively tell the system otherwise.
And whether you even count as having left is not your call, it is decided by HMRC’s Statutory Residence Test, which looks at your days in the UK and the ties you keep, not at where you feel you live. Getting this wrong is the single most expensive mistake a leaver makes. We cover the test itself in full in Under 183 Days: How UK Tax Residency Really Works.
The rest of this guide assumes you have checked the test and genuinely qualify as leaving. The job now is to make that departure official and tidy.
Next step: Before filing anything, confirm you actually meet the residence test for the year you are leaving. Everything below only works if you are genuinely becoming non-resident.
2. 🧾 The P85: the one form most people need
For most leavers, the key document is the P85, officially “Leaving the UK, getting your tax right.” It does two jobs at once: it tells HMRC you have gone, and it claims back any income tax you overpaid through PAYE in the part of the year you worked before leaving.
The essentials:
📝 Who it’s for: people who do not usually complete a Self Assessment tax return (Section 3 covers those who do). If your affairs are simple, PAYE salary and not much else, this is you.
💻 How to file it: online once you have left the UK, or by post. If you have not left yet, GOV.UK says you must print and post it. Include Parts 2 and 3 of your P45 from your final UK employer, if you have one.
💷 The refund: because you leave partway through the year but keep your full tax-free Personal Allowance (£12,570), you have often overpaid, and the P85 is how you claim it back.
⏳ Timing: there is no formal deadline, and HMRC's reply-date checker currently shows about three weeks to process it, online or by post. Sooner is better, but you can file after you have gone.
Next step: If you are on simple PAYE, get your P45 from your employer and file the P85, online once you have left or by post if you file before you go. It is the single most useful thing you can do to close your UK tax year cleanly, and it often comes with a refund attached.
