Last Updated: April 2026
The United Kingdom is one of the most significant moves an American can make — whether for work, family, or lifestyle. The US and UK have one of the most sophisticated bilateral tax relationships of any two countries, with a comprehensive 2001 tax treaty, a Totalization Agreement, and strong information-sharing infrastructure. But for Americans, the UK also means navigating one of the world’s most complex residence tests and, since April 2025, adapting to a completely redesigned foreign income regime that replaced the long-standing non-domicile system.
This guide covers the UK Statutory Residence Test (SRT), the new Foreign Income and Gains (FIG) regime that launched April 2025, the US-UK tax treaty and its unique super-credit provision, National Insurance, pension planning, and FBAR obligations for all UK financial accounts.
The UK Statutory Residence Test (SRT), introduced in 2013, replaced the old common law residency rules. It is considerably more complex than a simple 183-day rule, though 183 days is still a bright-line automatic trigger. Understanding your status under the SRT in your year of arrival is essential — most Americans benefit from professional advice for the arrival year.
You are automatically NOT a UK tax resident if you meet any of these: (1) fewer than 16 days in the UK in the tax year (or fewer than 46 days if you were not UK resident in any of the previous 3 tax years); (2) you work full-time overseas with fewer than 91 UK work days and fewer than 31 UK workdays. If you meet the Automatic Overseas Test, no further analysis is needed — you are non-resident. Note: UK tax year runs April 6 to April 5.
You are automatically a UK tax resident if: (1) 183+ days in the UK in the tax year — this is the most common trigger for Americans who move to the UK; (2) your only home is in the UK and you spend at least 30 days there; (3) you work full-time in the UK with fewer than 31 personal days and an average of 35+ hours/week. If you meet any Automatic Residence condition, you are UK resident regardless of other factors.
If you fall between the automatic tests (more than 16 days but under 183), you must count your UK “ties”: accommodation tie (have accessible accommodation in UK that you use); family tie (spouse/civil partner or minor child resident in UK); work tie (working 40+ days in the UK); 90-day tie (spent 90+ days in UK in either of the previous 2 tax years); country tie (UK is the country you spent most time in that year, relative to other countries). The number of ties combined with number of UK days determines residency. For example: if you spent 120 days in the UK and have 3 ties — you are UK resident. This analysis requires a careful diary of UK days and tie status. Year of arrival split-year treatment is available — allowing you to be non-resident for the part of the year before you arrive.
The April 2025 FIG (Foreign Income and Gains) regime is the most significant change to UK international tax in decades. It replaced the previous non-domicile remittance basis system, which had allowed long-term UK residents to shelter foreign income from UK tax if they didn’t bring it into the UK. The non-dom system was abolished with effect from April 6, 2025.
The FIG regime provides: in your first 4 tax years of UK tax residency (provided you were not UK tax resident in any of the previous 10 tax years), you can elect to pay 0% UK income tax and 0% capital gains tax on foreign income and foreign capital gains. The election is made on the UK self-assessment tax return for each year. You do not need to keep foreign income or gains offshore — unlike the old remittance basis, you can bring money to the UK freely without triggering tax. This is a substantial improvement over the old system for new arrivals.
For Americans arriving in the UK from April 2025 with no UK residency in the prior 10 years: during the first 4 years of UK residency, you elect into FIG. Your US-source income (dividends, interest, capital gains, US pension distributions, rental income from US property) is 0% taxable in the UK during those 4 years. Your UK-source employment income is still taxable in the UK normally. After 4 years: you become fully UK-taxable on worldwide income — UK transition rules apply. The FIG regime essentially gives new arrivals a 4-year grace period to restructure their affairs — a major planning opportunity for high-net-worth Americans with significant US investment portfolios relocating to the UK. Work with a UK tax advisor in the year you arrive to ensure you make the FIG election correctly on your first UK self-assessment return.
The FIG regime does not affect your US tax obligations. You still owe US tax on all worldwide income as a US citizen. The FIG regime reduces your UK tax bill (potentially to zero on foreign income for 4 years), which means less UK tax to credit against your US liability via the Foreign Tax Credit. For some Americans in the FIG period, the US may actually collect more tax (because there is less UK tax to credit), even though UK tax is zero. Run a full calculation with your expat CPA — the interaction is non-trivial.
The US-UK income tax treaty of 2001 is one of the most comprehensive US bilateral treaties. Key provisions: employment income taxed in country of work; business profits taxed based on permanent establishment; dividends: 15% withholding (5% for 10%+ corporate shareholders); interest: 0% withholding; royalties: 0%; pensions (critical for Americans): UK pension income (including SIPP and final salary schemes) generally taxable only in the UK for UK residents; US pension income (401k, IRA) generally taxable only in the US for US-citizen UK residents — though this requires careful treaty claim; capital gains: generally taxed in country of residence. The Savings Clause means the US reserves the right to tax its citizens as if the treaty did not exist, which limits pure treaty-shopping. However, the treaty’s mechanism for preventing actual double taxation is strong.
The US-UK treaty contains a unique provision (Article 24(6)) that tops up the Foreign Tax Credit in cases where UK tax exceeds US tax on the same income — the so-called ‘super-credit.’ This provision effectively ensures that Americans in the UK are never in a worse position than if only US tax applied, and creates carry-forward credits where UK tax is high. This is particularly valuable for Americans in the UK’s 40–45% brackets where UK tax significantly exceeds US tax rates.
Americans with US 401k or IRA accounts moving to the UK face complex questions: UK pension contributions (employer or personal into a SIPP) are generally deductible in the UK. US 401k contributions made while working in the UK — a UK employer may contribute to a 401k equivalent if they have US payroll, but this is less common than SIPP contributions. Taking US IRA or 401k distributions while a UK resident: under the treaty, these are generally taxable only in the US (as a pension from the source country). UK pension distributions (SIPP) for a UK resident are generally taxable only in the UK. Keep meticulous records of all contributions and their tax treatment in both countries to ensure correct treaty treatment.
A National Insurance (NI) number is the UK equivalent of a Social Security Number — required to work, access benefits, and file tax returns. Apply online through the UK government website (gov.uk). Processing can take several weeks. Americans working in the UK on a visa should apply for their NI number immediately upon arrival. National Insurance contributions: employees pay 12% on earnings between £12,570 and £50,270 and 2% above. Employers pay 13.8% on earnings above £9,100. Under the US-UK Totalization Agreement, Americans on short-term assignments (typically up to 5 years) with a US Certificate of Coverage continue contributing to US Social Security and are exempt from UK National Insurance. Those on longer-term or permanent moves without a Certificate of Coverage pay into UK National Insurance.
Register for UK self-assessment at HMRC (His Majesty’s Revenue and Customs) once you establish UK residency. Self-assessment is required if you have: income from self-employment; rental income; foreign income (even if claiming FIG relief, you must still file to make the election); income above £100,000 (personal allowance phase-out); certain investment income. UK tax return (Self-Assessment) deadline: October 31 for paper returns; January 31 for online returns (for the April 5 year-end). Working with a UK chartered accountant (CA) or US/UK dual-qualified tax advisor is strongly recommended, especially in the year of arrival when split-year treatment and FIG elections are at stake.
All UK bank and financial accounts (Barclays, HSBC, Lloyds, NatWest, Santander UK, Monzo, Starling, etc.) must be reported on FinCEN Form 114 (FBAR) annually if aggregate value exceeds $10,000 at any point. Also report UK ISA (Individual Savings Account) accounts, UK investment accounts, and UK pension accounts (SIPP) if they constitute foreign financial accounts above the threshold. FBAR is filed by June 15 (auto-extended to October 15) via FinCEN’s BSA E-Filing System. FATCA Form 8938 also applies if foreign financial assets exceed $200,000 at year-end/$300,000 at any point (single filers abroad). UK financial institutions report US account holders to HMRC under FATCA — non-compliance is easily detected.
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Transfer Money USA ↔ UK →Yes. US citizens owe US federal income tax on worldwide income regardless of where they live. Moving to the UK does not end your US filing obligation. The US-UK 2001 tax treaty and the Foreign Tax Credit (crediting UK taxes paid against US liability) prevent most practical double taxation. The treaty’s unique ‘super-credit’ provision tops up your FTC where UK tax exceeds US tax on the same income. Most Americans in the UK’s higher and additional rate bands owe little or no additional US tax after FTC, but Form 1040 filing is mandatory every year.
The FIG (Foreign Income and Gains) regime launched April 6, 2025, replacing the old non-domicile remittance basis. If you are in your first 4 years of UK tax residency (and were not UK resident in the prior 10 years), you can elect on your UK self-assessment return to pay 0% UK tax on foreign income and gains. This is generally beneficial for Americans with significant US investment income, as it eliminates UK tax on that income during the 4-year window. However, the interaction with US FTC obligations means you need to model the combined US+UK tax position — less UK tax means less FTC, potentially increasing US liability during the FIG period. Consult a US/UK dual-qualified tax advisor in your first UK tax year.
The UK SRT has three tiers: (1) Automatic Overseas Test: you are NOT UK resident if under 16 days in the UK (or 46 days if non-resident for 3 prior years); (2) Automatic Residence Test: you ARE UK resident if 183+ days in the UK; (3) Sufficient Ties Test: for day counts between those thresholds, the number of ‘UK ties’ (accommodation, family, work, 90-day, country) determines residency. Most Americans who permanently move to the UK will be in the UK 183+ days and automatically qualify as UK residents. The important planning is around the year of arrival — the UK offers split-year treatment, so you are only UK-taxable from the date you arrive, not from the start of the UK tax year (April 6).
US 401k and IRA accounts continue to exist and are subject to US rules. Under the US-UK treaty, distributions from US pension/retirement accounts (including 401k and IRA) are generally taxable only in the US as pension income from the source country — not in the UK, even if you are a UK resident. This is a significant treaty benefit. Contributions to UK pensions (SIPP) while working in the UK are UK-deductible but may not be deductible for US purposes. The interaction between US and UK retirement accounts requires careful planning — particularly around the 25% tax-free lump sum available from UK pensions, which the US may not treat as tax-free. Do not take pension distributions or make major changes to US retirement accounts before consulting a dual-qualified US/UK CPA.
It depends on your employment situation and whether you have a US Certificate of Coverage. Under the US-UK Totalization Agreement, Americans on short-term assignments (typically up to 5 years) from a US employer can obtain a Certificate of Coverage from the SSA, maintaining US Social Security coverage and exempting them from UK National Insurance. Americans working for a UK employer on a long-term or permanent basis typically pay into the UK National Insurance system instead of US Social Security. In both cases, you avoid double social security contributions. If you are self-employed in the UK, UK Class 4 NI contributions (9% on profits £12,570–£50,270; 2% above) apply unless covered by a Certificate of Coverage.