Double taxation — being taxed on the same income by two countries — is the defining concern of US-UK cross-border tax planning. As a US citizen or green card holder living in the UK, you are subject to US taxation on your worldwide income and UK taxation on your UK-source income (and often your worldwide income as a UK tax resident). Understanding exactly how both countries coordinate their taxing rights — and how to legally minimise double taxation — is the core of our work.
Why Double Taxation Occurs for US-UK Dual Residents
The US taxes its citizens and green card holders on worldwide income regardless of where they live — the only major country besides Eritrea to use citizenship-based taxation. The UK taxes residents on their UK-source income and (for most residents) worldwide income as well. The result: US citizens living in the UK face potential taxation by both countries on the same earnings.
The Three Mechanisms for Avoiding Double Taxation
1. The Foreign Tax Credit (Form 1116)
The Foreign Tax Credit is the primary mechanism for most US expats in the UK. The FTC provides a dollar-for-dollar credit against US tax for income taxes paid to the UK. Because UK income tax rates (20%–45%) are generally at least as high as US rates on the same income, the FTC typically eliminates US income tax liability entirely on employment and business income.
Key advantages: FTC can be applied to all income types (not just earned income), preserves IRA contribution eligibility, and generates carry-forward credits for future use against US tax on investment income.
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2. The Foreign Earned Income Exclusion (Form 2555)
The FEIE allows qualifying expats to exclude up to $130,000 (2025) of foreign-earned income from US taxable income entirely. Unlike the FTC, the FEIE provides a below-the-line exclusion — it removes income from the tax base rather than crediting taxes paid. While simpler, the FEIE is typically less beneficial for UK expats because it generates no credits, cannot shelter investment income, and reduces IRA contribution capacity.
3. The US-UK Tax Treaty
The US-UK Tax Treaty allocates primary taxing rights between the two countries for specific income types — pensions, dividends, royalties, employment income for temporary workers, and others. However, the treaty’s Saving Clause significantly limits its usefulness for US citizens: the US can generally still tax its citizens as if the treaty did not apply, meaning the treaty does not reduce US tax liability for most US citizens in the way it does for non-US persons.
Double Taxation and Dual Citizenship
The US-UK situation is particularly common for individuals who are both US and UK citizens (dual nationals). Key points for US-UK dual citizens:
- Both nationalities create ongoing obligations: A US citizen living in the UK as a UK national must file US returns annually, maintain FBAR/FATCA compliance, and potentially pay US tax on UK-source income — even if they have lived in the UK for decades and have no connection to the US other than their passport.
- Renunciation is a major step: Some long-term UK residents consider renouncing US citizenship to end their US tax obligations. Renunciation has serious consequences including an expatriation exit tax under IRC Section 877A. This is covered by our cross-border planning services.
- Green card holders must also file: Long-term US permanent residents (green card holders) who have lived in the UK for extended periods may face both US and UK obligations — and may be treated as covered expatriates upon abandoning their green card.
UK Residence and Domicile: How the UK Taxes You
Understanding your UK tax status is essential for dual-taxation planning:
UK Statutory Residence Test (SRT)
The UK’s Statutory Residence Test determines whether you are UK-resident for tax purposes. The test is complex and fact-specific, but broadly:
- Spending 183+ days in the UK in a tax year automatically makes you UK-resident
- Fewer days may still result in UK residence depending on ties to the UK (home, family, work)
- Non-UK residents are taxed only on UK-source income
UK Domicile and the Remittance Basis
Historically, UK non-domiciliaries could claim the remittance basis, paying UK tax only on foreign income brought into the UK. From April 2025, the UK abolished the non-dom regime and replaced it with a residence-based system. Under the new rules:
- New arrivals to the UK benefit from a 4-year Foreign Income and Gains (FIG) exemption — foreign income and gains are exempt from UK tax for the first 4 tax years of UK residence, regardless of domicile.
- After 4 years, individuals are taxed on worldwide income as UK residents.
- This change significantly affects US expats who were relying on non-dom status.
Specific Double Taxation Scenarios
UK Salary / Employment Income
Both the US and UK tax UK employment income. Solution: Foreign Tax Credit on Form 1116, using UK PAYE taxes paid as the credit. For most UK earners, this eliminates US income tax entirely on employment income.
UK Investment Income (Dividends, Interest)
UK dividends and interest may be taxed by both countries. The FTC can credit UK taxes, but passive income limitations may apply. ISA income has no UK tax (and thus no FTC available), making it fully US-taxable — a significant disadvantage for US persons holding ISAs.
UK Property and Capital Gains
Gains on UK property are subject to UK capital gains tax and US capital gains tax. The FTC can shelter US tax using the CGT paid. Important: UK CGT reporting deadlines (60-day rule for residential property) are separate from US reporting, which occurs on the annual Form 1040.
UK pension Income
The US-UK Treaty’s Article 17 pensions provisions are the primary planning tool for US expats receiving or planning to receive UK pension income. The interaction between UK pension taxation, US treatment of pension distributions, and the 25% tax-free lump sum is highly complex. See our US-UK Tax Treaty Guide and Cross-Border Planning services.