Americans Living in the UK: A U.S-UK Tax Survival Guide

The United States taxes its citizens wherever they live. The UK taxes its residents on their worldwide income. If you are an American living in the UK, you are inside both systems at once.

The good news is that double taxation is usually avoidable. The bad news is that several everyday UK financial products, ones your British colleagues use without a second thought, can create real U.S. tax costs. This guide walks through the essentials.

The basics: two returns, every year

Because the tax years do not line up, one UK tax year straddles two U.S. tax years. Coordinating the two returns is the single biggest thing that prevents mismatches and double tax.

How double tax is avoided

Foreign Tax Credit

The Foreign Tax Credit (Form 1116) lets you offset UK tax paid against U.S. tax on the same income. Because UK income tax rates are generally higher than U.S. federal rates, most employed Americans in the UK find their U.S. tax on UK salary drops to zero. Unused credits can usually be carried forward for up to 10 years.

Foreign Earned Income Exclusion

The Foreign Earned Income Exclusion (Form 2555) lets you exclude up to $132,900 of foreign earned income for 2026. It only covers earned income, not investment income or pensions.

For most UK residents the Foreign Tax Credit is the better choice, because UK tax is high enough to cover the US bill and excess credits build up for later years. Once you revoke the exclusion, you generally cannot claim it again for five years, so the choice deserves thought. Claiming the exclusion also blocks the refundable part of the U.S. Child Tax Credit, which the Foreign Tax Credit route keeps, so families with children usually do better with the credit.

The US–UK tax treaty, and its "saving clause"

The treaty decides which country can tax each type of income, especially pensions. But it contains a saving clause: the U.S. keeps the right to tax its own citizens as if the treaty did not exist, with limited exceptions. That is why many UK tax breaks do not carry across to your U.S. return.

Trap 1: ISAs are not tax-free for Americans

An ISA is completely free of UK tax. The U.S. does not recognise it. Interest, dividends and gains inside an ISA are taxable on your U.S. return each year.

Worse, because no UK tax is paid inside the ISA, there is no UK tax to credit. Your U.S. liability on that income is a real cost.

• Cash ISA: interest is ordinary U.S. income. Simple to report, but taxable.
• Stocks and Shares ISA holding funds: most UK and Irish-domiciled funds and ETFs are PFICs (see Trap 2).
• Lifetime ISA and Premium Bonds: also, not tax-free for U.S. purposes.

Trap 2: PFICs, the punitive fund rules

A Passive Foreign Investment Company is, broadly, any non-U.S. pooled fund. That includes UK unit trusts, OEICs and most UK or European-listed ETFs, whether held in an ISA or a normal account.

PFICs carry punitive U.S. tax rules, interest charges on deferred gains and a separate Form 8621 for each fund every year. Many Americans in the UK hold individual shares instead or hold US-domiciled funds through a U.S. brokerage. If you already hold UK funds, have them reviewed, since certain elections can reduce the U.S. tax cost but depend on timing and on information the fund may not provide.

Trap 3: U.S. funds can create a UK problem too

The mirror image also applies. Many U.S. mutual funds and ETFs do not have UK "reporting fund" status. When a UK resident sells them, gains can be taxed in the UK as income (up to 45%) rather than as capital gains (up to 24%).[GB1.1]

Some investments therefore suit neither country well. Choosing investments that work on both sides is one of the most valuable things a cross-border adviser can do.

Pensions: mostly good news, with one disputed area

• UK workplace pensions: under the treaty, contributions to a UK workplace pension can generally be excluded from U.S. taxable income within limits, and growth inside the pension is not taxed by the U.S. as it accrues.
• U.S. 401(k)s and IRAs: growth is generally not taxed in the UK while it stays in the plan.
• U.S. Social Security: under the treaty, U.S. Social Security paid to a UK resident is taxable only in the UK, even for U.S. citizens. The UK State Pension, by contrast, is taxed in both countries, with a U.S. credit for the UK tax.
• Roth IRAs: the treaty can protect a Roth's tax-free status in the UK. Making new contributions after you become UK resident can put that at risk, so take advice first.
• The 25% UK tax-free lump sum: this is tax-free in the UK, but the U.S. may tax it. How the treaty applies here is disputed, and the answer depends on your facts. Plan before you take any lump sum.

Reporting obligations: where penalties start

Missed information returns cause more trouble than unpaid tax. The main ones:

• FBAR (FinCEN 114): required if the combined value of your non-U.S. financial accounts exceeded $10,000 at any point in the year. This includes UK current accounts, savings, ISAs and some pensions.
• Form 8938 (FATCA): for those living abroad, generally required if foreign financial assets exceed $200,000 at year end or $300,000 at any time ($400,000 and $600,000 for married couples filing jointly).
• Form 8621: one for each PFIC.
• Form 5471 or 8858: if you own or control a UK limited company or certain other foreign entities.
• Form 3520: if you receive gifts or inheritances totalling more than $100,000 in a year from a non-U.S. person, such as a British parent or spouse. There is no tax, but penalties for missing the form are steep.

Penalties for missing these forms can be severe, even where no tax is due. If you are behind, the IRS offers streamlined procedures for non-wilful cases that can bring you up to date with reduced or no penalties.

Other points worth knowing

• Net Investment Income Tax (3.8%): applies to higher earners' investment income. Under the current IRS position, foreign tax credits generally cannot offset it, so it can be a genuine extra cost.
• Social security: the U.S.-UK totalisation agreement generally means you pay into only one system at a time, usually where you work.
• The UK's four-year FIG regime: Americans arriving in the UK after 10 years of non-residence may be able to exempt foreign income from UK tax. But if no UK tax is paid, there is nothing to credit in the U.S., and you lose your UK personal allowance. That said, U.S. tax rates are often lower than UK rates, so paying only U.S. tax on that income can still leave you better off. It is not always a good deal for U.S. citizens, so model it first.
• U.S. LLCs: the UK may treat a U.S. LLC differently from the US, which can create mismatches. Get advice before using one while UK resident.
• Inheritance and estate tax: the U.S. and UK have an estate and gift tax treaty. Long-term UK residents can face UK inheritance tax on their worldwide estate as well as U.S. estate tax exposure.

A quick checklist

1. File both a U.S. return and, where needed, a UK return every year.
2. Choose between the Foreign Tax Credit and the Foreign Earned Income Exclusion deliberately.
3. Avoid UK funds and fund-based ISAs unless you have modelled the PFIC impact.
4. File your FBAR and Form 8938 on time.
5. Get advice before taking a UK pension lump sum or contributing to a Roth IRA.
6. Keep the two returns consistent: the same income, the same exchange rates, the same treaty positions.

Coordinating U.S. and UK Taxes

For Americans living in the UK, tax planning involves understanding how two different systems interact. Decisions about income, investments, pensions and tax credits in one country can have consequences in the other.

At FRESH, our U.S. CPA and UK tax adviser work together to provide a coordinated view of both systems, including tax planning and filing obligations.

This article is general information and is not tax or legal advice. Figures are correct as of 27 October 2026.

Sources: 

IRS – Tax inflation adjustments for 2026 

IRS – Figuring the foreign earned income exclusion 

GOV.UK – U.S.-UK tax treaty