UK-US Tax Treaty: A Complete Guide

The UK-US Double Taxation Convention (the treaty) is one of the most important bilateral tax agreements in the world. It governs the tax treatment of income and gains between the two countries and provides mechanisms for resolving disputes. For individuals and businesses with connections to both the UK and the US, understanding the treaty is essential for managing tax exposure and compliance obligations in both jurisdictions.

Key Provisions of the Treaty

The UK-US treaty covers income tax, capital gains tax, and corporation tax. It allocates taxing rights over different types of income and provides relief from double taxation through foreign tax credits. Key provisions include:

• Dividends: withholding tax limited to 15% generally, 5% for companies holding at least 10% of voting stock, and 0% for certain pension funds
• Interest: generally exempt from withholding tax in the source country
• Royalties: withholding tax limited to 0% for most royalties
• Capital gains: generally taxable only in the country of residence, except for gains from real property
• Employment income: taxable in the country where the employment is exercised, subject to the 183-day rule
• Pensions: generally taxable only in the country of residence

Residency Tie-Breaker

The treaty's tie-breaker clause determines your residence for treaty purposes if you are considered resident in both countries under domestic law. The hierarchy is: permanent home, centre of vital interests, habitual abode, and nationality. If none of these resolve the issue, the competent authorities of both countries must attempt to reach a mutual agreement.

The tie-breaker is particularly important for US citizens living in the UK. The US taxes its citizens on worldwide income regardless of residence, so US citizens are always US resident for US tax purposes. The treaty can override this in certain situations, determining that an individual is UK resident for treaty purposes and limiting the US's right to tax specific types of income.

The Savings Clause

The treaty contains a savings clause that preserves the right of each country to tax its own residents and citizens as if the treaty had not come into effect. This means the US can continue to tax its citizens on worldwide income even if the treaty allocates taxing rights to the UK. However, the treaty provides foreign tax credits that prevent double taxation, so the UK tax paid on UK-source income can be credited against the US tax liability on the same income.

The savings clause has important exceptions. For example, the US agrees not to tax certain UK pensions and social security payments received by US citizens resident in the UK, and certain employment income earned by US citizens working in the UK is exempt from US tax if certain conditions are met.

Social Security Totalisation Agreement

The UK-US Social Security Totalisation Agreement prevents dual social security contributions and ensures that periods of coverage in both countries count toward eligibility for benefits. If you work in both countries during your career, the agreement allows you to combine your UK and US social security records to qualify for retirement, disability, and survivors benefits.

Under the agreement, you are generally covered by the social security system of the country where you work. If you are sent to work in the other country temporarily (up to five years), you can remain in your home country's social security system under a certificate of coverage. Self-employed individuals are generally covered by the country of residence.

FBAR and FATCA for UK Residents

US citizens and green card holders living in the UK must comply with US reporting requirements for foreign accounts and assets. The Foreign Account Tax Compliance Act (FATCA) requires UK financial institutions to report accounts held by US persons to HMRC, which then shares the information with the IRS. The Report of Foreign Bank and Financial Accounts (FBAR) requires you to report non-US financial accounts exceeding $10,000 in aggregate to FinCEN.

Failure to file FBARs can result in penalties of up to $100,000 or 50% of the account balance. The streamlined filing compliance procedures allow certain non-resident US citizens to catch up with their filing obligations with reduced penalties.

State Tax Considerations

The treaty applies to US federal taxes but does not prevent individual US states from imposing their own taxes. If you are resident of a US state with an income tax (such as California, New York, or Massachusetts), you may be required to file state tax returns even if you live in the UK. Some states respect the treaty's residency tie-breaker, but others do not.

If you maintain a driver's licence, voter registration, or property in a US state, that state may claim you are still a resident for tax purposes. Severing state ties is an important step when moving to the UK to avoid ongoing state tax liabilities.

Browse more UK international tax and cross-border guides or try our calculators.