Residence comes first
Whether you keep paying UK tax depends on the Statutory Residence Test, which is applied separately to each tax year. Spend 183 or more days in the UK in a tax year and you are automatically UK resident and taxable on worldwide income. In the year you leave, split-year treatment may divide the year into a UK part and an overseas part, but only if you meet one of HMRC's specific cases, such as starting full-time work overseas or ceasing to have a UK home. You claim it on the SA109 residence pages, and it shelters foreign income from the split point onwards, not UK income.
What the UK still taxes once you are non-resident
Becoming non-resident generally switches off UK tax on your foreign income and gains, but UK-source items remain taxable. UK rental profits stay in charge through the Non-Resident Landlord Scheme (register with form NRL1 to receive rent gross), and disposals of UK property must be reported and any tax paid within 60 days of completion. Most UK pensions stay within UK tax rules, and the 5-year temporary non-residence rule can claw certain gains, pension withdrawals and close-company dividends back into UK tax if your absence does not exceed five years. Tell HMRC you are leaving using form P85, or the SA109 pages if you file Self Assessment.
Thailand taxes you too
Thailand has its own charge. Spend 180 days or more there in a calendar year and you become Thai tax resident, taxable on Thai-source income and on foreign income you remit into Thailand; since 1 January 2024, remitted foreign income is taxable in the year of remittance if it arose on or after that date. The UK-Thailand treaty also has no pensions article, so private UK pensions are not cleanly protected from Thai tax on remitted income. Thai rules are moving and a proposed relaxation remains unenacted, so confirm your Thai position with a qualified local adviser and read our full Moving to Thailand tax guide.
