Moving to the US from the UK: The Tax Returns Before and After You Go
Two tax years that never line up, a US start date set by your first day in the country, and ISAs and pensions that become reportable overnight. Here is the return-by-return order for a Briton relocating to America.
The date you close the front door matters to HMRC, while the date you land matters to the IRS, so note both before the boxes go.
Written by the US UK Tax Experts team, cross-border tax specialists
Moving to US from UK: an introduction
Moving to the US from the UK means filing in two systems whose tax years never meet. Britain looks at the tax year from 6 April, and the US looks at the calendar year. Your last UK year can usually be split at departure. Your first US year starts on a date fixed by US rules, not by your visa or your removal van.
This article supports our guide to the US-UK double taxation treaty, which explains how the two countries share the right to tax you. Here we set out the returns themselves, in the order they fall due. We cover the UK leaver's return, the US arrival year and the reporting your British savings attract once you count as a US resident.
Why moving to the US from the UK is a sequencing problem
Most relocation guides list tasks. However, the hard part is timing. The UK return for your departure year and the US return for your arrival year cover different months. Furthermore, one US option cannot be claimed until you have spent most of the following year in America. Consequently, the order of filing matters as much as the content.
Who this article is for
We write for British nationals and dual nationals who are not yet US citizens or green card holders, moving for work or family. US citizens returning home face different rules, and we leave them aside. We also assume you were UK resident before you left. Wealth planning is outside our scope: we prepare and file the returns.
When does HMRC stop taxing you as a UK resident?
Usually from the day after you leave, if one of the split year cases applies. Otherwise you stay UK resident for the whole tax year. Split year treatment is the rule that divides one UK tax year into a UK part and an overseas part.
The statutory residence test comes first
The statutory residence test is the law that decides whether you are UK resident for a tax year. HMRC's RDR3 guidance note on the statutory residence test explains it. Most people who leave part-way through a year are still resident for that year. Therefore the question becomes whether the year can be split. That is the first decision in moving to the US from the UK.
Case 1 and Case 3 for most leavers
Three cases cover departures. Case 1 is starting full-time work overseas. Case 2 covers the partner of someone who does. Case 3 is ceasing to have a UK home. HMRC's manual page on Case 3, ceasing to have a home in the UK, requires you to be resident in the previous year and non-resident in the next. After the home goes, you must spend fewer than 16 days in the UK that year. Within six months, you must also become tax resident in, live in, or have your only home in the new country.
The empty flat problem
Case 3 fails if you keep a UK home. Many people moving to the US from the UK keep one. For example, a flat left empty for return visits may still count as a home. In our experience, this is the commonest reason a leaver's split year claim is challenged. Letting the property on a proper tenancy changes the picture, but HMRC weighs the facts.
What do you tell HMRC when you leave?
Tell HMRC through form P85 if you do not file Self Assessment, or through the residence pages of your return if you do. Either way, keep evidence of your departure date. Boarding passes and a completion statement both help.
Form P85 for employees
GOV.UK's guidance on getting your Income Tax right if you are leaving the UK (P85) covers employees who do not usually file a return. You include Parts 2 and 3 of your P45 if you have one. As a result, HMRC can stop your tax code and refund any overpayment from the months before you left.
Self Assessment and form SA109
If you file Self Assessment, you claim non-residence and split year treatment on the SA109 residence pages. GOV.UK's page on telling HMRC you are leaving sets out who must notify. Similarly, rent from a UK flat you keep means a UK return each year after you go.
Gains and the five-year rule
Temporary non-residence is a rule that can tax gains made abroad when you return. HMRC's HS278 helpsheet on temporary non-residents explains when it bites. In short, it can apply if you come back within five years. Therefore keep records of any disposal made while you are away.
When does the IRS start treating you as a US resident?
On your residency starting date, which is usually your first day in the US in the year you pass a residence test. Before that date you are a nonresident alien. After it, your worldwide income counts on a US return.
The substantial presence test
The IRS page on the substantial presence test sets two limbs. You need at least 31 days in the US in the current year. In addition, you need 183 days over three years, counting all current days, a third of last year's and a sixth of the year before. If you arrive in late summer, you will often fail it in your first year. That outcome surprises many people moving to the US from the UK.
The green card test
If you hold a green card, you are resident from your first day in the US as a lawful permanent resident. IRS Publication 519, the US tax guide for aliens, also covers anyone who passes both tests. In that case the earlier of the two dates applies.
The ten-day allowance
A house-hunting trip before the move need not start your residence early. Publication 519 lets you exclude up to 10 days of presence if your tax home and closer connection were still abroad. However, you must file a signed statement to use it. Without one, your first day in the country is your starting date.
Should you make the first-year choice?
Only if the numbers favour it, so model both ways. The first-year choice is an election that makes you US resident from arrival in a year when you fail the substantial presence test. It creates a dual-status year instead of a fully nonresident one. For people moving to the US from the UK alone, it often adds work without saving tax.
The conditions
Publication 519 requires at least 31 days in a row in the US in the arrival year. You must also be present on at least 75% of the days from the start of that period to 31 December. Finally, you must pass the substantial presence test in the following year. Consequently, you cannot file until you have met that test.
Waiting to file
If the following year's test is not met by the April deadline, you file Form 4868 for an automatic extension. Meanwhile, Publication 519 asks you to pay the tax you expect to owe as if you were a nonresident all year. Once made, the choice cannot be revoked without IRS consent.
What a dual-status return gives up
The IRS page on taxation of dual-status individuals is blunt. You cannot use the standard deduction. In addition, you cannot use head of household rates or file jointly unless you elect to. Married couples can choose full-year residence together if both meet Publication 519's conditions at year end. That election brings in worldwide income for the whole year, including the UK months.
What happens to your ISAs and UK pension once you are a US resident?
They stay open, but the US taxes them differently from HMRC. This is the part of moving to the US from the UK that people most often miss. From your residency starting date, ISA income and gains are reportable in the US. Your UK pension, by contrast, gets treaty protection for its growth.
ISAs lose their shelter in America
GOV.UK confirms that you can keep your ISA open after moving abroad, with UK relief continuing. However, you cannot pay in once you are non-resident, and you must tell your provider. The treaty does not mention ISAs, so the IRS taxes the interest, dividends and gains inside them.
Funds inside an ISA are often PFICs
A passive foreign investment company, or PFIC, is a non-US fund or company that earns mainly investment income. Most UK unit trusts and OEICs fall into that class. A US person who holds one files Form 8621 in the years the rules require. Our PFIC reporting service prepares those forms.
Workplace pensions and Article 18
Article 18 of the US-UK income tax treaty stops the US taxing growth inside a UK scheme until you draw it. Article 18(2) can also give US relief for contributions while you work in the US, if you joined the scheme before you arrived. Notably, Article 1(5)(b) withholds that contribution relief from anyone admitted for permanent residence. As a result, a green card holder may lose relief a visa holder keeps.
Which US reporting starts on arrival?
FBAR reporting and, above certain thresholds, Form 8938 start from your residency starting date. Both report your UK accounts; neither is a tax by itself. After moving to the US from the UK, most people need at least the FBAR.
The FBAR
FinCEN's page on the report of foreign bank and financial accounts applies once your accounts together exceed $10,000 at any time in the calendar year. Current accounts, savings, ISAs and many pensions all count. Moreover, it is filed online with FinCEN, not with your tax return.
Form 8938 for new residents
The IRS comparison of Form 8938 and FBAR requirements gives the US-living thresholds. For a single filer, that is over $50,000 at year end or over $75,000 at any time. The Form 8938 instructions say a part-year resident's reporting period starts on the residency starting date. Our page on FBAR and FATCA reporting covers both forms in more detail.
Consider a typical case: Hannah's first two years
Consider a typical case, offered as an example only. Hannah is a British national living in Leeds. Her employer transfers her to its Denver office on a work visa. She lands on 3 August 2026 and sells her Leeds flat that month.
Her UK leaving year
Hannah is UK resident for 2026/27 under the statutory residence test. Her new job looks full-time, so Case 1 is likely to split the year. If it fails, Case 3 may still apply, because she no longer has a UK home. She is employed with no other income, so she files a P85 with her P45. She also keeps her cash ISA and a stocks and shares ISA holding two UK funds.
Her first US year
From 3 August to 31 December 2026, Hannah spends 151 days in Denver. That falls short of 183, so she fails the substantial presence test for 2026. Without an election, she is a nonresident for 2026 and reports only her US salary. With the first-year choice, she becomes resident from 3 August. In that case her ISA income, FBAR and Form 8938 all start in 2026.
How we would model it
We would prepare 2026 both ways. Because Hannah is single, the dual-status return gives her no standard deduction, and the election adds reporting. Therefore she may be better off as a nonresident for 2026. From 1 January 2027 she is resident anyway, and every reporting duty starts then. Her workplace pension remains sheltered under Article 18, and her two ISA funds go on Form 8621.
The order to file in: a step-by-step sequence
Here is the sequence we use when moving to the US from the UK, built from the rules above. Dates assume an August arrival.
Before you fly
First, note your exact departure and arrival dates and keep your boarding passes. Second, decide whether your UK home is sold, let or kept, because that settles Case 3. Third, gather year-to-date UK pay, savings and pension statements. Fourth, stop ISA subscriptions once you will be non-resident.
In the first months
Next, file the P85 or diarise the SA109 with your return. Then list every UK account and its highest balance from your US start date. If you might use the first-year choice, also count your US days monthly so you can prove the 31-day and 75% tests.
The following spring and autumn
In the first April after arrival, file the US return, or extend it if you are waiting for the first-year choice. After that, file the FBAR by its automatic October deadline if it applies. Finally, an online UK return for your leaving year is due by 31 January after the tax year ends, if you file one. The two returns should show the same departure facts.
How US UK Tax Experts can help
US UK Tax Experts prepares your UK leaving return and your first US returns from one set of figures, so the two agree. We work out your residency starting date and test the split year cases. We also model the first-year choice both ways and prepare the FBAR, Form 8938 and any Form 8621. Our US and UK tax returns page explains how we prepare both sides together. For pensions, see our UK and US pension reporting service. If you are choosing between states, our article on state tax after a UK move covers the state side.
Conclusion
The tax side of moving to the US from the UK turns on two dates. Your departure date shapes the UK split year. Your arrival date, tested against US day counts, sets when America begins to tax you. ISAs and fund holdings become reportable from that US date, while a UK pension keeps its treaty shelter. Settle the dates first and model the first-year choice before you file anything.
Contact us
If you are moving to the US from the UK this year, email hello@usuktaxexperts.com or use our contact page. Tell us your departure date, your arrival date and your visa type. We reply within one working day.
Frequently asked questions
Usually only on UK income such as rent, once the overseas part of your split year begins. Your US salary is not taxed in the UK after that date. If no split year case applies, you stay UK resident for the whole tax year and the treaty settles any overlap.
Usually on your first day in the US in the year you pass the substantial presence test or the green card test. If you arrive after midsummer, you often fail the test in your first year. In that case you are a nonresident that year unless you make the first-year choice.
It is an election to be treated as a US resident from arrival in a year you fail the substantial presence test. You need 31 consecutive days in the US and presence on 75% of the remaining days, and you must pass the test the next year. It suits some people and not others, so model it both ways.
Yes, GOV.UK lets you keep it open, but you cannot pay in once you are non-resident. The US does not recognise the ISA, so its income and gains go on your US return. Funds held inside it are often PFICs and need Form 8621.
Yes, if you are a US resident for any part of the year and your foreign accounts together exceed $10,000 at any time. The obligation starts with your US residency. It is filed online with FinCEN, separately from the tax return.
Growth inside a UK scheme is not taxed in the US until you draw it, under Article 18 of the treaty. Contribution relief while working in the US is narrower and is not available to green card holders. The pension may still need to appear on an FBAR and Form 8938.
Use P85 if you are an employee who does not usually file Self Assessment. Include Parts 2 and 3 of your P45 so HMRC can refund any overpaid tax. If you file Self Assessment, you report leaving on the SA109 residence pages instead.
