US Expat Taxes in the UK: The Complete 2026 Guide

If you are a US citizen or green card holder living in the United Kingdom, you face tax obligations in both countries. The United States taxes its citizens on worldwide income regardless of where they live, and the UK taxes residents on their worldwide income under a progressive system with rates reaching up to 45% (and up to approximately 48% in Scotland under its devolved bands). Without careful planning, you could end up paying tax twice on the same income.

This guide covers the essential topics for US expats in the UK: the US-UK tax treaty, the ISA trap, UK pension and SIPP treatment, FBAR and FATCA reporting for UK accounts, choosing between the Foreign Tax Credit and the Foreign Earned Income Exclusion, the PFIC trap with UK investment funds, National Insurance under the Totalization Agreement, key deadlines, and the most common mistakes expats make.

The US-UK Tax Treaty (2001)

The Convention Between the Government of the United States of America and the Government of the United Kingdom of Great Britain and Northern Ireland for the Avoidance of Double Taxation was signed in 2001 and entered into force in 2003. It is widely regarded as one of the most comprehensive US tax treaties in force, particularly for its treatment of pensions. For a broader explanation of how bilateral tax treaties work, see our double taxation treaties guide.

Employment Income (Article 14)

Salary and wages are generally taxable in the country where the work is performed. If you live and work in the UK, the UK has the primary right to tax your employment income. The US also taxes it because of citizenship-based taxation, but you can claim a Foreign Tax Credit on Form 1116 for UK income taxes paid, which typically eliminates your US tax liability on that income entirely.

Pensions (Articles 17 and 18)

The pension provisions of the US-UK treaty are notably favourable. UK employer pensions and personal pensions (including SIPPs) generally receive treatment broadly equivalent to a US qualified retirement plan under the treaty: contributions by and on behalf of the employee may be deductible or excludable on the US return (subject to limits), and investment growth inside the pension is generally treated as tax-deferred for US purposes. Pension income paid from a UK pension to a UK resident is generally taxable only in the UK.

One important caveat: UK rules allow pension holders to take up to 25% of their pension pot as a tax-free lump sum. The US tax treatment of that lump sum is contested and uncertain. The IRS has not issued definitive guidance, and different tax professionals take different positions. Before taking a pension lump sum, obtain advice from a cross-border tax specialist who has reviewed your specific treaty analysis.

Dividends (Article 10)

Dividends from UK companies paid to a US resident in the UK are subject to a reduced withholding rate of 15% under the treaty (5% for corporate shareholders owning 10% or more of the paying company). File a W-8BEN with any US broker to claim reduced treaty withholding on US-source dividends.

Capital Gains (Article 13)

Gains from the disposal of personal property (stocks, funds, etc.) are generally taxable only in the country of residence. If you live in the UK and sell US securities, the UK has the primary taxing right. Real estate gains are taxed in the country where the property is located.

US Social Security (Article 17(3))

Under Article 17(3) of the treaty, US Social Security benefits paid to a UK resident are taxable only in the UK — the US does not tax them. In practice you stop US withholding by filing a Form W-8BEN with the Social Security Administration / paying agent, and you disclose the treaty position on Form 8833 with your US return.

The ISA Trap: Tax-Free in the UK, Taxable in the US

This is the most misunderstood area for US expats in the UK. Individual Savings Accounts — both Cash ISAs and Stocks & Shares ISAs — are entirely tax-free for UK purposes. Interest, dividends, and capital gains inside an ISA are not subject to UK tax. However, the IRS does not recognise that shelter. The US-UK tax treaty does not contain a provision extending treaty benefits to the ISA wrapper, and no US statute exempts ISA income from US tax.

As a result, for US persons:

• Interest earned in a Cash ISA is currently taxable on your US federal return in the year it is earned.
• Dividends and capital gains inside a Stocks & Shares ISA are currently taxable on your US return — and the funds inside the ISA are almost certainly PFICs (see below), which creates additional punitive US tax obligations.

Opening a Stocks & Shares ISA as a US person is therefore a double trap: the income is US-taxable, and the holdings are likely PFICs. If you already hold a Stocks & Shares ISA, consult a cross-border tax advisor about the PFIC implications before your next US filing.

The PFIC Trap: UK Funds Are Toxic for US Taxpayers

A Passive Foreign Investment Company (PFIC) is any non-US fund (or company) where 75% or more of income is passive, or 50% or more of assets produce passive income. In practice, the following UK and European investment vehicles are PFICs:

• OEICs (Open-Ended Investment Companies)
• Unit trusts
• Investment trusts (closed-ended funds listed on the LSE)
• Any fund held inside a Stocks & Shares ISA
• European UCITS ETFs domiciled in Ireland, Luxembourg, or the UK

Some LSE-listed ETFs do issue a PFIC Annual Information Statement (AIS), which can support a QEF election — but most do not. Without an AIS, the only available PFIC elections are the punitive default Section 1291 regime or the mark-to-market regime. Under Section 1291, gains are spread over your holding period and taxed at the highest marginal rate for each year, plus an interest charge. Effective tax rates on PFIC gains can reach 50-70%.

The simplest solution: hold US-domiciled ETFs (Vanguard, iShares, or Schwab US-listed ETFs) in a US brokerage account. These are not PFICs and receive standard US capital gains treatment. For a deep dive on the PFIC rules and the Form 8621 filing requirement, see our PFIC and Form 8621 guide.

FBAR for UK Accounts

If the aggregate maximum balance of all your foreign financial accounts exceeds $10,000 at any point during the calendar year, you must file an FBAR (FinCEN Form 114). The threshold is calculated by adding the highest balance reached in each account during the year, converted to USD at the Treasury year-end exchange rate.

Most US expats in the UK exceed this threshold easily. The following UK account types are reportable:

• Current accounts at any UK bank — including Barclays, HSBC UK, Lloyds, NatWest, Monzo, Starling Bank, and other challenger banks.
• Cash ISAs — reportable as foreign financial accounts even though they are held at a UK bank and are UK tax-free.
• Stocks & Shares ISAs — reportable, and the underlying holdings also raise PFIC and potentially FATCA Form 8938 issues.
• SIPPs (Self-Invested Personal Pensions) — generally reportable on the FBAR, though the IRS has occasionally taken inconsistent positions on certain pension accounts. Most practitioners report them.
• NS&I products(National Savings & Investments) — Premium Bonds, NS&I savings accounts, and investment accounts are all reportable.

The FBAR is filed electronically through the BSA E-Filing System, separate from your tax return. ExpatFolio tracks your foreign account balances and alerts you as you approach the $10,000 aggregate threshold.

FATCA Form 8938: Specified Foreign Financial Assets

Beyond the FBAR, you may also need to file FATCA Form 8938 with your federal tax return. Thresholds for expats living abroad are significantly higher than for domestic filers:

• Single filers living abroad: file if foreign financial assets exceed $200,000 on the last day of the year or $300,000 at any point during the year.
• Married filing jointly living abroad: thresholds are $400,000 on the last day of the year or $600,000 at any point.

Form 8938 covers a broader range of assets than the FBAR. In addition to bank accounts, you must report foreign securities (including ISA holdings), interests in foreign entities, and financial instruments issued by foreign persons. Yes, you may need to file both the FBAR and Form 8938 for the same accounts — they are separate requirements with different procedures, thresholds, and penalties.

Foreign Tax Credit vs. Foreign Earned Income Exclusion

US expats have two primary tools to avoid double taxation: the Foreign Tax Credit (FTC) on Form 1116 and the Foreign Earned Income Exclusion (FEIE) on Form 2555. For most Americans living in the UK, the FTC is the better choice. For a detailed comparison, see our FEIE vs. FTC guide.

The UK's income tax rates run up to 45%at the additional rate in England, Wales, and Northern Ireland, and Scotland's devolved income tax system reaches approximately 48% at the top rate. When your effective UK rate exceeds your US effective rate — which it typically does for most UK residents — the FTC eliminates your US tax liability entirely and generates excess credits that can be carried forward for up to 10 years.

The FEIE allows you to exclude up to $132,900 (2026 amount, indexed annually) of foreign earned income. However, it provides no benefit for investment income, and because it reduces your US taxable income, it can limit the value of UK tax credits that exceed the US tax on that income. In a high-tax jurisdiction like the UK, the FTC almost always produces a better result.

You cannot use the FTC and FEIE on the same dollar of income. Splitting them — for example, FEIE on earned income and FTC on investment income — is technically permissible but requires careful analysis and professional advice.

National Insurance and the Totalization Agreement

The US-UK Totalization Agreement, in force since 1985, coordinates Social Security coverage so workers do not pay into both systems simultaneously. The general rule: you contribute to the system of the country where you work.

• If you are employed by a UK employer in the UK, you pay UK National Insurance contributions and are exempt from US FICA (Social Security and Medicare) taxes.
• If you are temporarily posted to the UK by a US employer for up to 5 years, you can remain in the US Social Security system by obtaining a Certificate of Coverage from the SSA.
• If you are self-employed in the UK, you pay Class 2 and Class 4 National Insurance and are generally exempt from US self-employment tax.

The agreement also allows you to combine work credits from both countries. If you worked 8 years in the US and 7 years in the UK, you may be able to combine them to qualify for US Social Security benefits (which require 40 credits, roughly 10 years of covered work).

Key Deadlines

• April 15: Standard US federal tax filing deadline. Tax owed is due by this date regardless of extensions — interest accrues from April 15.
• June 15: Automatic 2-month extension for US citizens and resident aliens living abroad. No form required — attach a statement to your return confirming you qualify. Interest still accrues from April 15 on any unpaid tax.
• October 15: Extended deadline if you file Form 4868. Most expats use this deadline to allow time to finalise their UK self-assessment figures first.
• April 15 / October 15 (FBAR): The FBAR due date is April 15 with an automatic extension to October 15. No form is needed to get the extension.
• May 31: UK employers must issue P60 forms (annual earnings summaries) following the April 5 tax-year end. Keep these — you will need them for your US Foreign Tax Credit calculation.
• January 31: UK self-assessment online filing deadline for the prior UK tax year (April 6 – April 5). The UK tax year runs April 6 to April 5, not the calendar year — this mismatch requires careful coordination with your US return.

Common Mistakes US Expats Make in the UK

• Assuming an ISA is tax-free on both sides: Many expats open a Stocks & Shares ISA assuming it provides the same tax shelter as a US Roth IRA. It does not. Income and gains inside an ISA are currently US-taxable, and the underlying fund holdings are almost certainly PFICs.
• Not filing a US return: Living in the UK does not exempt you from US filing obligations. You must file if your income exceeds the standard filing thresholds, regardless of where you live or whether you owe any US tax.
• Forgetting the FBAR: A single UK current account can push you over the $10,000 aggregate threshold. Non-willful failure to file can result in penalties of $10,000 per violation.
• Investing in UK or European funds: OEICs, unit trusts, investment trusts, and UCITS ETFs are PFICs. The Section 1291 default PFIC regime can push effective tax rates well above 50%. Hold US-domiciled ETFs instead.
• Using the FEIE instead of the FTC: In a high-tax country like the UK, the Foreign Earned Income Exclusion typically produces a worse outcome than the Foreign Tax Credit.
• Mishandling the pension lump sum: The UK's 25% tax-free lump sum is attractive, but its US tax treatment is uncertain and contested. Do not assume it is also US-tax-free — seek specialist advice before taking it.
• Ignoring the UK tax year mismatch: The UK tax year runs April 6 to April 5. Your UK self-assessment will span two calendar years, requiring careful allocation of income when computing your US Foreign Tax Credit on Form 1116.
• Not reporting NS&I Premium Bond prizes: UK Premium Bond prizes are tax-free in the UK but are taxable interest income on your US return.

Navigating the US-UK tax landscape is demanding, but with the right structure it is entirely manageable. Keep your investments in US-domiciled funds, track your UK accounts carefully for FBAR and FATCA compliance, use the Foreign Tax Credit to offset double taxation, and work with a cross-border tax professional who understands both systems. For comparison with another common expat destination, see our US expat tax guide for France.