Moving Abroad Tax Checklist: US to UK and UK to US

A moving abroad tax checklist for the US and UK has four stages: decisions to make before you leave, the split year of the move itself, your first full year of reporting, and the rules that apply if you come back. The steps differ by direction, because the US taxes citizens wherever they live while the UK taxes on residence.

Why does the direction of the move matter?

The direction matters because the two countries decide who they tax in different ways. The United States taxes its citizens and green card holders on worldwide income from all sources wherever they live, so an American moving to London never leaves the US system. The United Kingdom taxes on residence, so a Brit moving to New York can leave the UK system for most income and join the US one.

The tax years add a second layer. The US year is the calendar year; the UK year runs from 6 April to 5 April. A move in August falls in the middle of both, but in different "halves" of each, which is why the date on the ticket can change what each country taxes. Our pre-move tax planning for moving abroad between the US and UK starts from that date.

Stage	US to UK	UK to US
Before you go	Review investments and state residency; plan UK residence start	Tell HMRC; deal with UK funds and ISAs; consider pre-move sales
Year of the move	UK split year; US return on worldwide income as normal	UK split year; US dual-status year
First full year	UK Self Assessment where needed; US return, FBAR, Form 8938	US return, FBAR, Form 8938; UK return if UK income continues
If you return	US filing continues throughout	UK temporary non-residence rules on gains

What should be on your moving abroad tax checklist before you leave?

The months before a move are when the cheapest decisions are available, because residence has not yet changed in either country. The checklist differs by direction.

Moving from the US to the UK

1. Plan your UK residence start. Under the Statutory Residence Test you are automatically UK resident if you spend 183 or more days in the UK in the tax year, if your only home is in the UK for 91 days or more in a row, or if you work full-time in the UK for a 365-day period.
2. Avoid building a PFIC problem. UK funds, including those held in an ISA, are usually passive foreign investment companies for a US citizen. Decide how you will invest in the UK before you open accounts, not after. Our article on ISAs and PFICs explains why.
3. Check your state. US states apply their own residency rules to people who leave, and some are harder to exit than others. Keep evidence of the move, such as a closed lease or sold home, a new UK address and changed registrations.
4. Look at the 4-year FIG regime. If you have not been UK resident for at least ten consecutive tax years, you may qualify for the 4-year foreign income and gains regime. Claiming it removes UK tax on qualifying foreign income and gains but costs you the Income Tax and Capital Gains Tax allowances. For an American still taxed by the US on the same income, that can be a poor trade.

Moving from the UK to the US

1. Tell HMRC. If you do not file Self Assessment, fill in form P85. If you do, use the residence section of your return, form SA109.
2. Deal with UK funds and ISAs. You can keep an ISA and it keeps its UK tax relief, but you cannot pay in while non-resident, and the US does not recognise it. UK funds inside it will usually be PFICs once you are a US resident.
3. Consider sales before you arrive. Assets with large gains are generally measured from what you paid for them once you are in the US system. Selling some before US residence starts can make sense, but check the UK temporary non-residence rules first.
4. Set up the Non-Resident Landlord Scheme. If you will let your UK home, your letting agent, or your tenant if there is no agent and the rent is over £100 a week, deducts basic rate tax unless HMRC approves an NRL1i application. You still declare the rent on a Self Assessment return.

How is the year of the move taxed?

The year of the move is usually taxed in parts on both sides. The UK's split-year treatment normally divides the tax year into a non-resident part and a resident part, so UK tax on foreign income applies only to the resident part. The US approach depends on who you are.

• US citizens moving to the UK have no split year in the US. The Form 1040 reports worldwide income for the whole calendar year, and UK tax paid after the move is relieved through the foreign tax credit on Form 1116 or, for earnings, the foreign earned income exclusion on Form 2555.
• Brits moving to the US normally have a dual-status year: nonresident until the residency starting date and resident afterwards. Residence starts under the green card test or the substantial presence test, which needs at least 31 days in the current year and 183 days over three years on a weighted count. IRS Publication 519 explains the restrictions, including no standard deduction in a dual-status year, and the elections that can change the result.

Illustrative example: a couple move from Manchester to Boston on 1 August 2026, with no earlier US visits that year. On the UK side, split-year treatment can make them non-resident from the day after they leave, so the 2026 to 2027 UK tax year is divided at 1 August. On the US side, their residency starting date is 1 August if they go on to meet the substantial presence test, so their 2026 US return covers worldwide income only from that date, unless they elect otherwise. Two tax years, two dividing lines, and one date that sets both.

Our guides for each direction go deeper: tax obligations for Americans living in the UK and the first-year tax guide for Brits moving to the US. If both countries claim you as resident at the same time, the treaty tie-breaker rules decide which one takes priority.

What changes in your first full year abroad?

The first full year is when reporting catches up with the move. For anyone in the US system, whether an American in the UK or a Brit now resident in the US, non-US accounts become foreign accounts. The FBAR, FinCEN Form 114, is required when their combined value exceeds $10,000 at any time during the calendar year.

Form 8938, the separate FATCA statement filed with the tax return, depends on where you live. According to the IRS summary of FATCA reporting, an unmarried taxpayer living in the US files when specified foreign financial assets exceed $50,000 on the last day of the year or $75,000 at any time, while an unmarried taxpayer living abroad files above $200,000 or $300,000. The same move can therefore switch the Form 8938 threshold up or down by a factor of four.

On the UK side, a new arrival who needs a Self Assessment return must tell HMRC by 5 October after the end of the tax year. For the 2025 to 2026 tax year, paper returns are due by 31 October 2026 and online returns and payment by 31 January 2027. Our guide to registering for Self Assessment by 5 October covers the process.

US deadlines run alongside. Americans abroad get an automatic extension to 15 June and can extend to 15 October with Form 4868, but interest runs on unpaid tax from 15 April. Pensions need their own review in the first year, particularly before any transfer or withdrawal; see how the treaty treats UK pensions.

What happens to Social Security and National Insurance?

Social security contributions follow different rules from income tax, and a move between the US and UK is covered by a separate agreement. The US/UK social security agreement, which the Social Security Administration summarises, generally assigns your work to one country's system so you do not pay into both for the same earnings.

For employees, the key question is whether the move is a posting or a permanent change. An employee sent by their employer from one country to work in the other for a period not expected to exceed five years can usually stay in the home country's system under the detached worker rule, supported by a certificate of coverage. Someone who is hired locally after the move normally joins the system of the country where they now work. Self-employed people need the same analysis before paying either National Insurance or US self-employment tax, because the agreement decides which one applies.

The agreement also lets periods of coverage in both countries be taken into account when working out entitlement to certain benefits later. That makes it worth keeping a record of where you worked and which system you paid into for each year, particularly if you expect to move more than once.

Illustrative example: an engineer is seconded from a London employer to its Chicago office for three years. With a certificate of coverage, the engineer can generally keep paying UK National Insurance and avoid US Social Security tax on the same salary for the secondment. If the same engineer resigned and joined a US company on arrival, US Social Security would normally apply from the first US payslip.

What if you move back?

Returning is where one of the least-known UK rules applies. Under HMRC's temporary non-residence rules, a person who had sole UK residence for at least 4 of the 7 tax years before leaving, and whose period of non-residence is 5 years or less, can have certain gains made while abroad treated as arising in the tax year of return. A sale planned "while non-resident" can therefore still be taxed in the UK if the move turns out to be short.

For Americans, the return trip changes less: US filing never stopped. What changes is the Form 8938 threshold, the end of any UK-specific relief, and state residency starting again.

What do people get wrong when they move?

• Treating the move date as a logistics decision. The date sets the split in both tax years, so it is a tax decision too.
• Opening UK investment accounts on autopilot. A US citizen who buys UK funds in their first month creates years of Form 8621 filings.
• Assuming non-resident means no UK return. UK rent and other UK income can keep a Self Assessment return running.
• Forgetting that ISAs and pensions count. They are reportable accounts for FBAR and Form 8938 purposes.
• Planning a short stay abroad around a gain. The temporary non-residence rules can bring it back into UK tax.

US/UK Cross Border Tax is US CPAs and UK tax advisers working as one team, with offices in London, Manchester, New York and San Francisco. A move is the point where a joined-up view saves the most, so we plan both sides together through our tax planning service. If you have a date in mind, talk to us before you book it.