US Tax Obligations for Expats Living in London: What You Must Report

For US citizens living in London or the UK, tax obligations can quickly become complex and, in many cases, overwhelming. Unlike most countries, the United States taxes its citizens based on citizenship rather than residency. This means that even if you live and work entirely in the UK, you are still required to report your income to the US authorities.

At the same time, you may also be subject to UK tax rules, creating a dual-reporting environment that requires careful planning and compliance. Failure to meet these obligations can result in penalties, interest, and increased scrutiny from tax authorities.

Understanding exactly what needs to be reported, and how the UK and US systems interact, is essential for staying compliant and avoiding unnecessary costs.

Why US Expats Must Still File Taxes

The US operates under a citizenship-based taxation system enforced by the Internal Revenue Service.

This means:

• All US citizens and green card holders must file annual tax returns
• This applies regardless of where they live or earn income
• Worldwide income must be reported

Even if no tax is ultimately owed, filing is still a legal requirement.

This is one of the most common misunderstandings among expats, many of whom assume that living abroad removes their US filing obligations. It does not.

What Income Must Be Reported

US expats in the UK must report all worldwide income, including:

• Employment income from UK employers
• Self-employment or business income
• Rental income from UK or overseas properties
• Investment income such as dividends and interest
• Pension income (depending on structure and withdrawals)

All income must be reported in US dollars, which requires currency conversion based on IRS-approved exchange rates.

Key Forms US Expats Need to File

Form 1040 (US Tax Return)

This is the main tax return filed annually with the Internal Revenue Service.

It includes:

• Personal details
• Income reporting
• Tax calculations
• Credits and deductions

Foreign Earned Income Exclusion (FEIE) – Form 2555

This allows expats to exclude a portion of their foreign-earned income from US taxation.

Key points:

• Applies only to earned income (not passive income)
• Requires meeting residency or physical presence tests
• Updated annually with a specific exclusion limit

Foreign Tax Credit (FTC) – Form 1116

This allows you to offset US tax liability using tax already paid in the UK.

In many cases, this prevents double taxation, particularly where UK tax rates are higher.

FBAR (Foreign Bank Account Report)

If the total value of foreign financial accounts exceeds $10,000 at any point during the year, you must file an FBAR with the Financial Crimes Enforcement Network.

This includes:

• UK bank accounts
• Savings accounts
• Investment accounts
• Joint accounts

Failure to file can result in significant penalties.

FATCA Reporting (Form 8938)

Under Foreign Account Tax Compliance Act, expats may also need to report foreign financial assets if they exceed certain thresholds.

This overlaps with FBAR but is filed as part of your tax return.

Understanding UK Tax Obligations

In parallel, US expats must comply with UK tax rules governed by HM Revenue and Customs.

UK tax obligations typically include:

• Paying income tax on UK earnings
• National Insurance contributions
• Reporting self-employment income (if applicable)
• Declaring capital gains

The UK tax year runs from 6 April to 5 April, which differs from the US calendar year system. This creates additional complexity when aligning reporting.

How Double Taxation Is Avoided

One of the biggest concerns for US expats is being taxed twice on the same income.

US-UK Tax Treaty

The US-UK Tax Treaty helps determine which country has primary taxing rights over certain types of income.

Foreign Tax Credits

As mentioned earlier, UK taxes paid can often be used to offset US liabilities.

Foreign Earned Income Exclusion

Provides additional relief by excluding qualifying income.

In practice, most expats do not pay double tax, but they must still file correctly to claim these benefits.

Common Mistakes US Expats Make

Many expats unintentionally fall out of compliance due to:

• Assuming they do not need to file US taxes
• Failing to report foreign bank accounts
• Not declaring UK pensions correctly
• Mixing up UK and US tax years
• Incorrect use of FEIE and FTC

These mistakes can lead to penalties and complications that are avoidable with proper guidance.

Penalties for Non-Compliance

The US takes offshore reporting seriously.

Potential consequences include:

• Financial penalties for late or missed filings
• FBAR penalties that can be substantial
• Interest on unpaid taxes
• Increased scrutiny from authorities

For those who have fallen behind, there are structured disclosure programmes available to become compliant.

Do You Always Owe Tax as a US Expat?

Not necessarily.

Many US expats in the UK end up owing little or no US tax due to:

• Higher UK tax rates
• Use of foreign tax credits
• Available exclusions

However, filing is still mandatory, even if the final tax liability is zero.

Special Considerations for UK-Based Expats

UK Pensions

Treatment varies depending on the type of pension and withdrawals.

ISAs (Individual Savings Accounts)

While tax-free in the UK, ISAs may not receive the same treatment in the US.

Property Ownership

Rental income and capital gains must be reported in both jurisdictions.

Self-Employment

Additional reporting requirements apply, including potential US self-employment taxes.

Why Professional Advice Is Often Necessary

Given the complexity of dual taxation systems, many expats benefit from working with specialists who understand both UK and US regulations.

Professional support can help:

• Ensure full compliance
• Optimise tax efficiency
• Avoid penalties
• Simplify the reporting process

FAQs

Do US expats in the UK have to file taxes every year?
Yes, all US citizens must file annually regardless of where they live.

What happens if I don’t file FBAR?
Penalties can be significant, even if no tax is owed.

Can I avoid paying tax twice?
Yes, through foreign tax credits and tax treaties.

Do I need to report UK bank accounts?
Yes, if the total exceeds $10,000 at any point during the year.