A move to the UK from the US often begins with practicalities such as visas and travel arrangements, but those steps are only the start. From a tax perspective, the more important issue is not the date of arrival, but when UK tax residence is triggered. That question is governed by strict rules and, for many US individuals, the answer is far less intuitive than expected.
Why US individuals are choosing the UK
The UK remains a compelling destination for US individuals, despite ongoing economic and political uncertainty.
Professional opportunities, family ties, lifestyle aspirations and the growth of global mobility continue to drive relocation decisions. The expansion of remote and hybrid working arrangements has added further complexity, blurring the line between temporary stays and permanent moves. Individuals can now spend extended periods in the UK without a definitive “relocation date” but from a tax perspective, this ambiguity can lead to significant and unexpected consequences.
Immigration status and tax residence: two separate systems
A common misconception among those relocating to the UK is that immigration status determines tax residence. It does not.
UK immigration law governs your right to enter, live and work in the UK. Tax residence, however, is determined exclusively by the Statutory Residence Test (SRT) — a separate framework that operates independently of immigration rules.
You may hold a UK work visa yet remain non-UK resident for tax purposes. Conversely, someone who views their stay as “temporary” (perhaps on a short-term visa) may nevertheless become UK tax resident if they spend sufficient days in the UK and accumulate enough UK ties.
The SRT does consider whether you planned to relocate permanently or simply to explore opportunities. Instead, the test focuses on objective criteria: days spent in the UK, whether you work here, whether you maintain UK accommodation, and whether close family members are present.
This disconnect matters. Immigration milestones (the start date of a visa, the commencement of UK employment, or a formal relocation) do not necessarily coincide with the start of UK tax residence. Many individuals assume tax consequences follow immigration status, only to discover that HMRC has been counting days from the outset.
Double the countries, not (always) the tax
Whilst the practical steps of relocating *securing employment, arranging visas and organising logistics) can feel substantial, the more intricate challenges often emerge after arrival, particularly concerning tax residence and reporting obligations.
The US determines tax residence using rules that operate on a calendar year basis, whilst the UK SRT is assessed by reference to the UK tax year (6 April to 5 April). Consequently, your residence position in the US and the UK may not align neatly, particularly during the year of arrival or departure. Periods of dual residence (where you are treated as tax resident in both jurisdictions simultaneously) are common. This misalignment in timing and methodology underscores why cross-border tax planning is crucial for US individuals moving to the UK.
For US citizens and green card holders, relocating to the UK does not sever ties with the US tax system. The US taxes its citizens on worldwide income regardless of where they reside, making dual filing obligations standard rather than exceptional.
This is where the UK–US double tax treaty becomes relevant, though it is frequently misunderstood.
The treaty determines which country has taxing rights over specific types of income and provides relief from double taxation, typically through foreign tax credits. However, it does not eliminate the obligation to file US tax returns, nor does it always prevent cash flow difficulties where tax is paid in one country before relief can be claimed in the other.
In cases of dual residence, the treaty’s “tie-breaker” provisions may determine treaty residence, but this does not override domestic tax rules entirely. Detailed analysis is required to establish which income is taxed where, how relief is claimed, and how timing and characterisation mismatches are managed.
The essential point: treaty protection should never be assumed. When applied correctly, the treaty prevents double taxation, but it does not eliminate tax liability.
The four-year tax window: a time-limited opportunity
From April 2025, the UK introduced a new framework for taxing foreign income and gains, replacing the longstanding remittance basis with the Foreign Income and Gains (FIG) regime. This development is particularly significant for US individuals relocating to the UK with non-UK investments or income streams.
Under the FIG regime, individuals who become UK tax resident and who have not been UK resident in any of the previous ten tax years may benefit from a four-year period during which qualifying foreign income and gains are exempt from UK tax, regardless of whether they are remitted to the UK. A formal claim must be made for the regime to apply.
This relief is strictly time-limited. Once the four-year period expires, you become subject to UK tax on worldwide income and gains as they arise, with no ability to shelter income by retaining it offshore.
For US individuals, the FIG regime presents a valuable but temporary window to review and restructure overseas assets. However, US tax obligations continue throughout this period, and income or gains exempt from UK tax may remain fully taxable in the US. Co-ordinating your UK and US tax positions is therefore essential to avoid inefficiencies or forfeited relief.
How Kingsley Napley can help
Our international Private Client team advises internationally mobile individuals, families and businesses on the UK tax implications of relocation, residence and cross-border activity. We work closely with Immigration, Employment and other specialist advisers within KN to deliver integrated advice that reflects the realities of modern mobility.
Whether you are planning a move, already dividing your time between countries, or concerned that your UK presence may have greater tax implications than anticipated, early advice can make a substantial difference.
