UK tax follows residence, and UK residence begins on a date the statute fixes rather than one you choose. Before that date the UK generally has no claim on your non-UK income and gains; from that date it generally does. The pre-arrival window is therefore the only period in which several decisions are open at all — the timing of a disposal, a bonus, a distribution or a pension event, and whether the four-year foreign income and gains regime is available to you.
Nothing here is a recommendation to realise, restructure or move anything. It is a list of questions to model with an adviser while they can still be modelled both ways.
Key takeaways
- GOV.UK draws the line plainly: if you are UK resident, you'll normally pay tax on your foreign income, and if you are not UK resident you will not.
- Residence is decided by the statutory residence test applied to facts, and split-year treatment is a set of statutory cases — not an election made on a return.
- The FIG regime runs for a maximum of four consecutive years from the start of UK residence, after at least ten consecutive tax years of non-UK residence. Unused years cannot be rolled forward.
- A US citizen remains taxable on worldwide income throughout, so accelerating a gain before arrival may move US tax forward rather than remove it.
- Foreign tax credits are capped at the US tax on foreign source income and carry back one year and forward ten, so US tax paid in a year with no UK tax is not automatically recovered.
- US trusts and closely held companies already carry reporting on Forms 3520 and 5471, and the UK may characterise the same structures differently. That review belongs before arrival.
- Inheritance tax now turns on long-term UK residence, and the years that count start accruing from your first year here.
The dividing line is a date, and the statute picks it
The UK's claim on worldwide income and gains switches on for a whole tax year unless a split-year case applies. GOV.UK sets out the automatic UK tests, which include that you spent 183 or more days in the UK in the tax year, that your only home was in the UK for 91 days or more in a row and you stayed in it for at least 30 days of the year, or that you worked full-time in the UK for any period of 365 days with at least one day falling in the year being tested.
Split-year treatment then divides the year of arrival: GOV.UK explains that when you move in or out of the UK, the tax year is usually split into 2 — a non-resident part and a resident part, so you only pay UK tax on foreign income for the resident period.
None of this is discretionary. HMRC's RDR3 guidance describes split year cases 1 to 3 for those leaving and cases 4 to 8 for those coming to the UK, and says each has its own set of conditions that must all be met for the case to apply. You do not choose a start date; your facts choose it, and those facts include when a home becomes available, when employment begins and when the family actually moves. We set out the mechanics on our UK residence and the statutory residence test page.
The two calendars also pull against each other. The UK tax year started on 6 April 2025 and ended on 5 April 2026; the US year is the calendar year. One autumn transaction can sit in a UK year and a US year that only partly overlap.
The FIG regime has to be understood before you land
From 6 April 2025, HMRC states that all UK residents are taxed on the arising basis of assessment on their worldwide income and gains. Against that background, eligibility for the FIG regime is effectively settled on the day you arrive: GOV.UK describes a qualifying claimant as someone still within their first 4 years as a UK tax resident following at least a 10-year period as a non-UK tax resident.
The regime runs for a maximum of four consecutive years beginning when UK tax residency started, and you cannot roll unused years over to a later year. A claim is made on the Self Assessment return, and making one costs you tax-free allowances for Income Tax and Capital Gains Tax, along with the Married Couple's Allowance, Marriage Allowance and Blind Person's Allowance where they would otherwise apply.
Three questions follow, and none can be answered afterwards:
- Does the ten-year history actually hold? Nationality and domicile do not affect eligibility, but a stray year of UK residence a decade ago can.
- Since the four years run from the start of residence whether or not a claim is made, which years are worth claiming, and what income is expected in each?
- If UK tax is relieved on foreign income, there is no UK tax on it to credit against the US liability — so how does the claim interact with the US return?
We cover the regime in full in the FIG regime and the US citizen moving to the UK. It belongs in a pre-arrival conversation rather than a first-return one because the shape of those four years is largely set before the move.
Assets standing at a gain: a question, not a step
This is the question raised most often, and raised badly most often. The UK charges capital gains tax on the gain when you sell or dispose of a chargeable asset, and a UK resident may pay it even where the asset is overseas. A non-resident pays UK tax on gains on UK land and property but generally not on other assets.
So the arithmetic looks obvious enough to be dangerous: a disposal on one side of the line may sit outside UK CGT, and the same disposal on the other side may not. The temptation is to read that as an instruction. It is not one. It is a modelling exercise, and the honest version includes:
- Whether the FIG regime would have covered the gain in any event, in which case a pre-arrival disposal bought nothing in the UK and may have cost something in the US.
- What the US consequence is, in the US tax year into which the disposal actually falls.
- Whether this is an asset you wanted to sell for commercial reasons, or one you would be selling only because of a date.
- Whether base cost and holding records will still be producible for two revenue authorities years later, and whether you may leave the UK again — GOV.UK notes that a non-resident can be brought back into charge on certain UK assets where they return within five years.
An adviser who reaches the answer before running those numbers is not advising, and a plan whose only rationale is a date deserves scepticism.
The United States does not pause while you plan
This is where transatlantic planning diverges from the version written for everyone else. The IRS is unambiguous that a US citizen is subject to tax on worldwide income from all sources, and that the filing rules are generally the same whether you are in the United States or abroad.
A pre-arrival realisation therefore does not remove tax. At best it changes which country taxes the gain; at worst it accelerates the US charge on something you were in no hurry to sell. Pulling a disposal forward can also move it across the line the IRS draws between short-term and long-term treatment, since a gain is long-term only where the asset was held for more than one year.
The credit mechanics compound this. The foreign tax credit is limited to the smaller of the amount of foreign tax paid or accrued, or the amount of U.S. tax attributable to your foreign source income, with unused foreign tax carried back one year and forward ten. US tax paid in a pre-arrival year, on income the UK never taxed, does not conveniently locate a UK credit later.
Nor does the treaty rescue a citizen. Article 1(4) of the 2001 convention allows a Contracting State to tax its residents and, by reason of citizenship, tax its citizens, as if this Convention had not come into effect. The residence tie-breaker settles treaty residence for other purposes; it does not release a US citizen from US tax.
Trusts and closely held companies deserve a look before, not after
Structures built for a US-resident life are rarely built for a UK-resident settlor or shareholder, and they are the slowest thing to review after a move. They also carry standing US reporting. Form 3520 is the Annual Return to Report Transactions with Foreign Trusts and Receipt of Certain Foreign Gifts, and Form 5471 is the Information Return of U.S. Persons With Respect To Certain Foreign Corporations, filed by certain US citizens and residents who are officers, directors or shareholders in certain foreign corporations.
The pre-arrival questions are about characterisation rather than compliance. Does the UK see the same entity the US sees, or does it look through it? Does a distribution that is neutral today become taxable once the recipient is UK resident? If the controlling mind of a company moves to London, what does that do to the company's own position? Our note on foreign trusts and Form 3520 for US persons in the UK covers the reporting limb.
None of this argues for unwinding anything. It argues for knowing, before you land, how each structure will look from both sides once you have.
Inheritance tax: the clock starts when you arrive
Inheritance tax used to follow domicile. It now follows residence, which means it starts counting on arrival. GOV.UK states that you are a long-term UK resident if you are tax resident in the UK for either the previous 10 consecutive years, or a total of 10 years or more within the previous 20 years. Long-term residence then persists after departure — up to 10 tax years, and shorter where fewer years were spent here.
For an affluent American arriving with substantial non-UK assets, that reframes the move. The early years are the planning years, and wills, trusts and lifetime gifting sit inside a window that closes quietly. We look at it in detail in UK inheritance tax and long-term residence for US citizens.
Banking, records and the evidence you will need
Less glamorous, and more often the thing that causes real trouble. Before arrival is the moment to establish which accounts hold what, and to be able to show — years later, to two revenue authorities — what was received before UK residence began and what came after.
Questions worth answering first include whether capital accumulated before arrival stays separately identifiable rather than blended with later income, whether broker statements will still produce base cost and acquisition dates after an account transfer, and what US foreign account reporting the new banking arrangements will trigger. Documentation assembled at the time is straightforward; documentation reconstructed years later rarely is.
When the conversation should happen
Months before the flight, not in the first UK return. By the time a return is being prepared, the residence start date is history, the disposals are done, the structures are as they are, and the adviser's role has narrowed to reporting what already happened. A pre-arrival meeting is different in kind: it models the year of arrival on both sides at once, tests the FIG position against the income actually expected, and identifies what must be decided before a date rather than after it. What follows is the moving year itself, covered in the moving year and your first US-UK tax return.
We run the US and UK analysis together rather than sequentially, because a pre-arrival decision that improves one return frequently worsens the other. A licensed CPA or Enrolled Agent reviews and signs off the US side; an ACCA-qualified accountant reviews the UK side. Our US-UK expat tax service is built for precisely this kind of move.
If a UK relocation is on the horizon — even a year out — that is the moment to book a confidential consultation, rather than the month you arrive.
This article is general information, not tax or legal advice, and does not create a professional relationship. Nothing in it is a recommendation to realise a gain, restructure an entity or move an asset. Pre-arrival planning is highly fact-dependent and the rules, rates and thresholds change; everything here should be confirmed against current official guidance and modelled on your own facts before you act.
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Reviewed by a CPA / Enrolled Agent. Last updated: 20 September 2026.
Official sources: GOV.UK Tax on foreign income | GOV.UK residence | HMRC RDR3 | GOV.UK 4-year FIG regime | HMRC RFIG41000 | GOV.UK Capital Gains Tax | GOV.UK IHT long-term UK residence | GOV.UK Self Assessment deadlines | 2001 UK-USA Convention | IRS US citizens and resident aliens abroad | IRS Topic 409 | IRS Topic 856 | IRS Form 3520 | IRS Form 5471
Frequently asked questions
When does UK tax residence actually start, and can I choose the date?+
You cannot choose it. Residence is decided by the statutory residence test applied to your facts. GOV.UK sets out automatic UK tests that include spending 183 or more days in the UK in the tax year, having your only home in the UK for 91 days or more in a row and staying in it for at least 30 days of that year, or working full-time in the UK for any period of 365 days with at least one day of that period in the year being tested. Where you arrive part-way through a year, the tax year is usually split into two parts - a non-resident part and a resident part - so that UK tax on foreign income applies only to the resident portion. But split-year treatment is not an election. HMRC's RDR3 guidance describes split year cases 1 to 3 for people leaving the UK and cases 4 to 8 for people arriving, and states that each case has its own set of conditions which must all be met for that case to apply. In practice the start date is driven by facts you control only indirectly - when a home becomes available to you, when employment begins, when the family moves - which is exactly why those facts are worth mapping before the move rather than after it.
What is the FIG regime, and why does it have to be understood before I arrive?+
From 6 April 2025, HMRC states that all UK residents are taxed on the arising basis of assessment on their worldwide income and gains. Against that background, the foreign income and gains regime allows individuals who come to the UK after at least 10 consecutive tax years of non-UK residence to claim relief on foreign income and gains arising in their first four years of UK residence. Two features make it a pre-arrival topic rather than a filing-season one. First, eligibility is fixed by history: the ten-year record of non-residence either exists on the day you land or it does not, and nationality, domicile and any previous use of the remittance basis do not change that. Second, the regime is available for a maximum of four consecutive years beginning when UK tax residency started, and unused years cannot be rolled over to a later year - so the value of the window depends on what income and gains actually arise inside it, which is largely determined by decisions taken beforehand. A claim is made on the Self Assessment return, and making one costs you tax-free allowances for Income Tax and Capital Gains Tax, together with the Married Couple's Allowance, Marriage Allowance and Blind
Should I sell my appreciated investments before I become UK resident?+
That is a question to model, not a step to take, and nothing here is a recommendation to sell anything. The reason it gets asked is real enough: the UK charges capital gains tax on the gain when you dispose of a chargeable asset, a UK resident may be within that charge even where the asset is overseas, and a non-resident generally pays UK tax on gains on UK land and property but not on other assets. So the timing of a disposal relative to the residence start date can change which country taxes the gain. The analysis rarely stops there. If the FIG regime would have covered the gain in any event, a pre-arrival disposal may have achieved nothing in the UK while costing something in the US. As a US citizen you remain taxable on worldwide income throughout, so accelerating a disposal usually moves the US charge forward rather than removing it, and it can pull the gain across the short-term and long-term line, since the IRS treats a gain as long-term only where the asset was held for more than one year. There are non-tax questions too - whether you wanted to sell at all, and whether base cost records will still be producible for two revenue authorities years later. Model it properly, and
Does moving to the UK reduce my US tax bill?+
Not by itself. The IRS states that a US citizen is subject to tax on worldwide income from all sources, and that the rules for filing income, estate and gift tax returns and paying estimated tax are generally the same whether you are in the United States or abroad. Leaving the country does not switch that off. The treaty does not switch it off either: Article 1(4) of the 2001 UK-USA convention allows a Contracting State to tax its residents and, by reason of citizenship, tax its citizens as if the convention had not come into effect. Relief for a citizen therefore runs mainly through the foreign tax credit rather than through exemption, and the credit is limited - the IRS describes it as the smaller of the foreign tax paid or accrued, or the US tax attributable to your foreign source income, with unused foreign tax carried back one year and carried forward ten. Two practical consequences follow for pre-arrival planning. Income that the UK does not tax generates no UK tax to credit. And US tax paid in a pre-arrival year, on income that the UK never taxed, does not neatly find a matching credit in a later year. Both are reasons to model the arrival year on both sides at once rather t
What happens to my existing US trust or closely held company when I become UK resident?+
It needs reviewing before you arrive, because these are the slowest arrangements to change and the most likely to be characterised differently on each side of the Atlantic. The US reporting obligations already exist and continue: Form 3520 is the Annual Return to Report Transactions with Foreign Trusts and Receipt of Certain Foreign Gifts, and Form 5471 is the Information Return of U.S. Persons With Respect To Certain Foreign Corporations, filed by certain US citizens and residents who are officers, directors or shareholders in certain foreign corporations. The pre-arrival questions are about characterisation rather than filing. Does the UK recognise the entity the same way the US does, or look through it? Does a distribution that is neutral today become taxable once the recipient is UK resident? If the person who controls a company moves to London, what does that do to the company's own position? And does the family's arrival in the UK convert arrangements that were purely domestic into cross-border ones with reporting on both sides? None of this is an argument for unwinding structures, and restructuring in haste before a move carries its own risks. It is an argument for knowing,
When does UK inheritance tax start applying to my worldwide estate?+
The clock starts on arrival, which is what makes this a pre-arrival topic. Inheritance tax used to follow domicile; it now follows long-term UK residence. GOV.UK states that you are a long-term UK resident if you are tax resident in the UK for either the previous 10 consecutive years, or a total of 10 years or more within the previous 20 years. Once that status applies, non-UK assets can come within the charge. It also persists for a period after you leave: GOV.UK indicates that long-term UK resident status can continue for up to 10 tax years after departure, with a shorter tail where fewer years were spent in the UK. For an American arriving with substantial non-UK assets, the practical consequence is that the early years of UK residence are the planning years. Wills, trusts, lifetime gifting and the interaction with the US estate and gift tax system all sit inside a window that closes without any notice being issued. It is also an area where the UK and US systems do not align neatly, so a plan drafted with only one of them in view can create difficulties in the other. Confirm the current rules and your own year count with an adviser before acting.
