The documents you need to return to HMRC to advise them of your intent to leave the country vary depending on your circumstances:
If you are in employment or are claiming Jobseeker’s Allowance, you need to submit HMRC form P85 – either online or by post – and accompany this with parts 2 and 3 of your P45 form.
If you normally complete a Self Assessment tax return – for example if you are self-employed – then you can inform HMRC of your intention to leave the country via your tax return (form SA109). This must take the form of a postal return, not online; and remember that the submission date for paper returns is earlier than for online returns – 31 October rather than 31 January – and you may be fined if you miss the deadline. (Note that although notification by online return isn’t allowed, you can submit your return via Self Assessment software.)
If you are going to be working abroad for a UK-based employer for at least one full tax year, then you need to submit both a P85 form and a tax return.
If you have savings accounts in the UK, tax is normally deducted automatically from any interest payments you receive. If you obtain form R105 from HMRC and send it to your bank or building society, they will stop automatically deducting tax while you are non-resident.
On receipt of your notification, HMRC will assess your tax status and make the necessary changes. If you leave the country and have non-resident status then you won’t pay UK tax on any non-UK income or gains. Be aware, however, that you may still have to pay tax on any UK-based income – for example if you let out your UK property and receive rental income.
If any of your circumstances change while you are abroad – such as a change of address or marital status – then you should contact HMRC with your National Insurance number and inform them of the change. You also need to let HMRC know if you return to live in the UK.