UK tax for Americans moving to the UK: residence, the FIG regime and your first tax return

When you move to the UK as an American, you do not swap one tax system for another. You add one. The IRS keeps taxing you as a US citizen, wherever you live, and HMRC starts taxing you as a UK resident.

From that point your income and gains are assessable under UK rules as well as US rules. Understanding residence, available reliefs and filing deadlines will help you manage both systems.

1. Residence and split year: where UK tax starts

Statutory Residence Test

The starting point for any American arriving in the UK is the Statutory Residence Test. It is the law that decides whether you are UK resident for a tax year, based on days spent in the UK, where you work and the ties you have here. The UK tax year runs from 6 April to 5 April, rather than the calendar year, and most people arrive part way through it.

Split year treatment

Split year treatment is what protects the foreign income and gains you earn before you arrive. If you qualify, the tax year is divided into an overseas part, taxed as a non-resident, and a UK part, taxed as a resident.

In practice, this means your US salary, investment income and gains arising before the move stay outside UK tax.

Split year is not automatic, and you must meet conditions to qualify. The three cases that cover most Americans are:

1. Starting full-time work in the UK, where the job runs for at least a year.
2. Starting to have a home in the UK, which you keep for the rest of that year and all of the following tax year.
3. Starting to have your only home in the UK, which you must keep until the end of the tax year.

Each case requires you to be below a day threshold driven by your ties to the UK before you arrive, scaled down depending on how early in the tax year you move.

2. The four-year FIG regime

The starting point once you are UK resident is that your worldwide income and gains are taxable in the UK, unless you qualify for the Foreign Income and Gains (FIG) regime.

FIG regime eligibility

If you were not UK resident in any of the ten tax years before you arrive, you qualify as a new resident and can claim relief from UK tax on your foreign income and gains for your first four tax years. For an American that covers US pension income, US investment income and US gains, and the money can be brought to the UK freely. Once the four years end, your worldwide income and gains are taxable in the UK in the normal way.

Employment income: Overseas Workday Relief

If you qualify as a new resident and some of your work duties are performed outside the UK, Overseas Workday Relief takes the portion of employment income relating to overseas workdays out of UK tax, for the same four years. Relief is capped at the lower of 30% of your qualifying employment income and £300,000 a year.

Self employment: all or nothing

Profits from a trade only qualify if the trade is carried on wholly outside the UK (RFIG45100). If any part of the business is managed or performed from the UK, all of the profits are taxable here.

The trade off

A claim is not free. For any year you claim, you lose your personal allowance of £12,570 and your capital gains annual exempt amount of £3,000 (RFIG43000). That applies however small the claim. Foreign losses arising in a claim year are not allowable. Run the numbers each year before ticking the box; the moving to the UK tax calculator compares worldwide taxation with a FIG claim side by side.

Deadlines to claim

FIG is claimed on a Self Assessment return using the SA109 residence pages, and the claim must state the exempt foreign income and gains.

The deadline is the anniversary of the 31 January after the end of the tax year (RFIG42300). For 2025/26 the return is due on 31 January 2027 and the claim deadline is 31 January 2028.

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3. Double tax: how the treaty works from the UK end

The UK US treaty contains a saving clause in Article 1 that lets the US tax its citizens as if the treaty did not exist. What survives it is Article 24, relief from double taxation, which decides for each type of income which country taxes first and which gives credit for the other's tax. HMRC's guidance is in its double taxation manual.

The table shows the position for a US citizen living in the UK.

Source: UK/US Double Taxation Convention and HMRC Double Taxation Relief Manual.

US social security is the one item the saving clause does not reach. Article 17(3) gives the taxing right to the country where you live, and Article 1(5) lists it as an exception to the saving clause, so once you are UK resident your social security is taxed only in the UK and the US does not tax it at all.

State tax is outside the treaty, but HMRC gives credit for it under its own rules where the state tax is a tax on income. HMRC's list of admissible US taxes includes California and New York personal income tax, New York City tax and the net investment income tax. Social Security and Medicare contributions are not creditable.

4. Registering for Self Assessment: the deadline is 5 October

If you have foreign income or gains, you must file a UK tax return, either to report your worldwide income and gains or to claim the FIG regime.

You must register with HMRC by 5 October after the end of your first tax year with foreign income or gains, so an arrival in 2026/27 means registering by 5 October 2027.

Register online using form SA1. Your Unique Taxpayer Reference usually arrives by post within 15 working days, or 21 if you are abroad.

The return is due by 31 October on paper or 31 January online, with the tax paid by 31 January. HMRC's free online service cannot file the residence pages that carry split year, FIG and Overseas Workday Relief, so you will need commercial software, an agent or a paper return.