The Statutory Residence Test: three questions, in order
Since 2013, UK tax residency isn't a judgment call — it's a flowchart. The Statutory Residence Test (SRT) asks three sets of questions in strict order, and the first one that gives a definitive answer wins.
First, the automatic overseas tests. Pass any one and you're non-resident, full stop:
- You spend fewer than 16 days in the UK in the tax year (this is the one for recent leavers — it applies if you were UK resident in any of the three previous tax years).
- You spend fewer than 46 days in the UK and weren't UK resident in any of the three previous tax years.
- You work full-time overseas, spending fewer than 91 days in the UK and keeping your UK workdays to a small handful.
Second, the automatic UK tests. If none of the above applies, pass any of these and you're resident:
- You spend 183 days or more in the UK in the tax year.
- Your only home is in the UK.
- You work full-time in the UK.
Third, if neither side settles it, you land in the sufficient ties test — the sliding scale that decides most real expat cases.
Sufficient ties: the sliding scale
The SRT recognises five ties to the UK:
- Family: a UK-resident spouse, partner or minor child.
- Accommodation: a place to stay in the UK available to you for 91 days or more, where you spend at least one night.
- Work: 40 or more days of the year working more than three hours a day in the UK.
- The 90-day tie: you spent more than 90 days in the UK in either of the two previous tax years — which every fresh leaver has by definition.
- The country tie (leavers only): the UK is where you spent more days than anywhere else that year.
The more days you spend in the UK, the fewer ties it takes to pull you back in. For someone who was UK resident in any of the last three years — that's you, the year you leave — the table looks like this:
| Days in the UK | Ties that make you resident |
|---|---|
| Fewer than 16 | None — automatically non-resident |
| 16 – 45 | 4 ties |
| 46 – 90 | 3 ties |
| 91 – 120 | 2 ties |
| 121 – 182 | 1 tie |
| 183 or more | Always resident |
Practical translation: a first-year leaver almost always carries the 90-day tie, and often family or accommodation too. With three ties, your safe allowance is 45 days in the UK; with two, it's 90. Summer weddings, Christmas and a work trip add up faster than people think — the expats who get this right count days in a spreadsheet, not from memory.
The year you leave: split-year and the P85
The UK tax year runs 6 April to 5 April, and residency normally applies to the whole of it. Split-year treatment is the fix: if you leave partway through and meet the conditions — typically starting full-time work abroad, or your only home shifting overseas — the year divides in two. The UK part is taxed as a resident's; from the overseas part on, only UK-source income stays in HMRC's reach. It applies automatically when the conditions are met, not by request.
Then there's the P85, the most underrated form in the whole move. If you don't file self-assessment, the P85 tells HMRC you've left and triggers the refund of income tax you overpaid through PAYE — your employer withheld all year as if you were staying, and you weren't. There's no statutory deadline, you can file it from Thailand, and refunds take a few months to land. If you do file self-assessment, you skip the P85 and report the departure in the residence pages of your return.
Pension, ISA, National Insurance: what travels and what doesn't
Three pieces of UK financial furniture, three different fates:
- Your pension travels — with an asterisk. Workplace and personal pensions can be drawn from Thailand, and the state pension gets paid abroad. But Thailand is one of the "frozen" countries: your state pension is paid at the rate of your first payment there, with no annual increases, because there's no social security agreement between the two countries. Over a 20-year retirement, that freeze compounds into real money.
- Your ISA survives but stops growing sideways. The account stays open and keeps its UK tax-free status, but once you're non-resident you can't add new money, and your provider needs to know you've left. And here's the part nobody mentions: Thailand doesn't recognise the wrapper. What HMRC calls tax-free, the Thai Revenue Department calls plain foreign income the moment you remit it as a Thai tax resident. Offshore, the ISA's magic is only half real.
- Your National Insurance record pauses — unless you feed it. Years abroad don't count toward the state pension by themselves. You can keep the record alive with voluntary contributions: the route for new overseas applications is Class 3, at £17.75 a week (2025/26 rates, around £923 a year). The cheaper Class 2 route closed to new overseas applications in April 2026. For context: 10 qualifying years gets you any state pension at all, 35 gets you the full one.
The 1981 treaty: thinner than you'd expect
The UK–Thailand double taxation agreement has been in force since 1981, and its age shows. Modern treaties usually have an article deciding which country taxes pensions. This one doesn't: outside of government-service pensions — which stay taxable only in the UK — the treaty is silent on pensions entirely.
The consequence is bigger than it sounds: there's no treaty relief for the UK state pension or for private pensions. Once you're a Thai tax resident, pension money you bring into Thailand is assessable there under the ordinary remittance rules, and the 1981 text doesn't step in to reassign it. The treaty still does useful work on other income — but on the income most British retirees in Thailand live on, it simply has nothing to say.
The other side: Thai tax residency
What you're exiting into is a much simpler machine. Spend 180 days or more in Thailand in a calendar year and you're a Thai tax resident — automatically, nothing to sign. From there, Thailand runs a territorial, remittance-based system: Thai income tax touches your local income and the foreign income you bring into the country, with brackets from 0 to 35% and the first 150,000 ฿ exempt. What counts as remitted money — and what doesn't, like savings you held before the move — becomes the question your whole tax year turns on. For a Brit arriving from a system that taxes worldwide income on sight, the logic inversion is the single biggest adjustment: in Thailand, what matters isn't what you earn. It's what you bring in.
Frequently asked questions
How many days can I spend in the UK without becoming resident again?
Depends on your ties. Under 16 days: automatically non-resident (for recent leavers). Then the scale: 16–45 days takes four ties to make you resident, 46–90 days three, 91–120 days two, 121–182 days one. At 183 days you're always resident.
Do I need to file a P85?
Only if you don't file self-assessment: it tells HMRC you've left and triggers any PAYE refund for your departure year. No statutory deadline, and it works from abroad. Self-assessment filers report the departure in their return's residence pages instead.
Can I keep my ISA from Thailand?
Yes, and it stays tax-free for UK purposes — but no new contributions once you're non-resident, and your provider needs to know. Thailand doesn't recognise the wrapper: remitted ISA income is ordinary foreign income to the Thai Revenue Department.
Does the treaty protect my state pension?
No. The 1981 UK–Thailand treaty has no pension article outside government-service pensions, so the state pension gets no treaty relief — as a Thai resident it's assessable when remitted. It's also frozen: paid abroad without annual increases.