US Expats in the UK: 5 Things Your British Accountant Won’t Tell You About Your IRS Obligations

From a flat in London to a terraced house in Manchester or a stone cottage outside Edinburgh, thousands of Americans have built a life in the United Kingdom. They pay council tax, contribute to workplace pensions and file their returns with HMRC on time. Many assume this settles their tax affairs. It does not.

The United States taxes its citizens and green card holders on worldwide income, wherever they live, and a UK accountant is usually trained to handle only the British side of the ledger. That gap is where problems begin. Below are five areas where UK advice tends to stop short, and what Americans abroad should know about them.

1. Your US Filing Requirement Continues Even When You Owe No Tax 

Understanding US tax obligations while living in the UK starts with one simple fact: the IRS generally requires US citizens and certain other taxpayers to report their worldwide income.

Moving to Britain does not end your duty to file a federal return. Most British accountants work from the UK tax year, which runs from 6 April to 5 April. The IRS works on the calendar year. The two calendars rarely line up, so income has to be recalculated for each system.

A few points worth keeping in mind:

• US citizens abroad get an automatic extension to mid-June, though any tax owed still accrues interest from April.
• Filing a return is required even if the foreign earned income exclusion or foreign tax credits bring your US bill to zero.
• Missing returns can quietly pile up penalties for years, and many expats only discover this when applying for a mortgage or a visa.

2. UK Tax Paid Does Not Always Cancel Out US Tax

Anyone researching UK taxes for US expats will hear about the foreign tax credit, but it works less smoothly than it sounds.

The foreign tax credit may allow you to offset US tax with eligible income taxes paid to HMRC. In many cases that removes most or all of the US liability. The catch is that the two countries define income differently, and the credit only applies to the same category of income.

Common sources of friction include:

• Different rates: If your UK rate is lower than the US rate on a given type of income, you owe the difference to the IRS.
• Different timing: Income recognized in one tax year in the UK may land in another year for the IRS.
• Currency swings: The IRS requires figures in dollars, so exchange rates on the day of each transaction matter, particularly when you sell property.

That last point surprises many homeowners. A UK house sold at a modest profit in pounds can show a different gain in dollars, or even a taxable gain where the UK shows none, because of how the pound moved against the dollar during ownership.

3. ISAs and UK Investment Funds Can Create Unexpected Problems

A good piece of tax advice for US expats in the UK should always cover what happens to savings and investment products that look tax-free at home.

Individual Savings Accounts are among the most popular wrappers in Britain, and rightly so. Gains and income inside an ISA are free from UK tax. The US does not generally recognize the UK’s tax-free treatment of ISAs. Income and gains in an ISA may still have to be reported on your US tax return.

The bigger trap is the type of fund held inside it. Many UK investment funds, including some unit trusts and OEICs, may qualify as passive foreign investment companies (PFICs) under US tax rules. 

Many Americans in the UK only learn about this after years of buying funds on the recommendation of a UK adviser who never mentioned it. Reviewing your portfolio early, and favoring US-recognized funds where possible, can save a great deal of trouble.

4. Pensions Are Treated Differently Across the Atlantic

Pension planning is one of the most misunderstood parts of US expat tax UK rules, because the benefits that are clear in Britain are far less clear to the IRS.

Workplace pensions, personal pensions and SIPPs are central to retirement planning in the UK. The US-UK tax treaty provides certain protections for pensions, but US tax treatment varies by pension type and individual circumstances. Contributions, investment growth, and withdrawals may be treated differently under US and UK rules. But there are several details your British accountant may not raise:

• Contributions: Your tax relief in the UK does not automatically translate into a US deduction.
• The 25% tax-free lump sum: Although this benefit is available under UK tax rules, its US tax treatment can differ depending on your circumstances.
• Reporting: Certain pension structures, especially those that look more like trusts, can trigger extra forms.
• Social security: The UK and the US have a totalization agreement, so you are normally covered by one system at a time, but the paperwork needs to be right.

Because the treaty also includes a saving clause that lets the US tax its own citizens, reading it carefully matters. A small mistake in how a pension is classified can echo for decades.

5. Your Bank and Investment Accounts Must Be Reported

Meeting US expat tax UK reporting standards means looking beyond your income and declaring the accounts that hold it.

British banks are required to share information about American account holders with US authorities, so the IRS often knows more than expats expect. Two separate reports are involved:

• FBAR: Generally required when the combined value of your reportable foreign financial accounts exceeds $10,000 at any point during the calendar year. 
• Form 8938: Required when your foreign financial assets pass higher thresholds, which are more generous for those living abroad.

These reporting requirements may cover bank accounts, ISAs, and certain other financial assets. FBAR and Form 8938 have different rules, and whether pensions or joint accounts must be reported depends on the circumstances.

Penalties for missing them can be steep, even when no tax is owed. A UK-only accountant may not routinely advise on these US reporting requirements, as neither report is part of the standard UK tax filing system.

Putting It All Together

Living in the UK as an American does not need to be stressful, but it does require thinking in two tax systems at once. A few habits go a long way:

• Keep a clear record of every account, pension and investment held in the UK.
• Check any new investment for its US tax treatment before you buy.
• File US returns every year, even when you expect to owe nothing.
• Speak to a tax professional who understands the tax rules in both countries. 

Americans abroad are often surprised to learn how much they can do to make the two systems work together. The earlier you understand your position, the more options you keep open.