Tax rules in the UK catch a lot of expats out. The UK has its own way of taxing income and reporting earnings, and it often works very differently from what you’re used to outside the UK.
Getting up to speed as soon as you arrive is very important. It’s how you protect yourself from hefty tax bills and missed deadlines.
And for most people moving to the UK, it all starts with Self Assessment.
Not sure how it works? Keep reading, because we’re walking you through when you need to file and what income HMRC expects you to report. We’ll also explain how to stay compliant while making full use of the tax reliefs available to you.
What Is a UK Self Assessment Tax Return?
In the UK, tax isn’t always taken from your income automatically. When HMRC needs you to report your earnings yourself, they use a system called Self Assessment.
A Self Assessment tax return is a yearly form where you declare:
- Your Worldwide Income: Both UK earnings and anything from overseas (especially relevant now that the non-dom system has been replaced).
- Capital Gains: Profit from selling assets like property or stocks.
- Allowable Expenses and Reliefs: This is where you claim things like the Foreign Tax Credit to avoid being taxed twice.
- Tax Already Paid: Any tax you’ve already settled via your employer (PAYE) or payments made to the IRS.
HMRC then uses this information to calculate your final bill or – if you’ve overpaid – issue a refund.
Does Every Expat Need to File a Self Assessment Tax Return
That’s a great question! While not everyone has to file, the net is much wider than most expats expect. You generally need to complete a Self Assessment return if any of the following applied to you the previous year:
- Overseas Income or Assets: This is the big one. If you have a rental property back home, a foreign pension, or even a savings account earning interest abroad, HMRC wants to know about it.
- The £1,000 Threshold: If you earned more than £1,000 from self-employment (side hustles) or gross property income, you’ve triggered a filing requirement.
- High Earners (£150k+): If your income from your UK job (PAYE) is over £150,000, you are now required to file a return, even if your tax is already being deducted by your employer.
- Investment and Capital Gains: Selling shares (even in a US brokerage) or property usually requires a filing.
- Multiple Income Streams: If you have more than one job or a complex mix of dividends and salary, Self Assessment is how HMRC makes sure you haven’t underpaid (or overpaid!) on tax.
- Child Benefit Charge: You had to pay the High Income Child Benefit Charge and do not pay it through PAYE.
How to Register and File Your First UK Tax Return
If you’ve determined you need to file, you’re legally required to notify HMRC by October 5th following the end of the tax year in which you first had reportable income. The UK tax year runs from 6 April to 5 April, so for the 2025/26 tax year, that deadline is October 5th 2026.
Get Your Unique Taxpayer Reference (UTR)
Register online through the GOV.UK website. You’ll need your National Insurance number (if you have one) and basic personal details. HMRC will then post a 10-digit UTR number to your home address.
Set Up Your Government Gateway
Once your UTR arrives, you can create a Government Gateway ID. HMRC will then post a separate activation code to your address. Note: If you are living abroad or have just moved, this can take 21+ days.
Complete the Return (Post-April 6th)
You can start your return as soon as the year ends. For the 2025/26 tax year, you can file any time after 6 April 2026.
Submit and Pay (The January 31st Deadline)
Your online return must be submitted, and all tax paid, by midnight on January 31st following the end of the tax year. For the 2025/26 year, your deadline is January 31st 2027.
Other Important Considerations for UK Expats
Before we wrap up, here are a few more top tips to keep in mind to save money, avoid high fees, and protect your income.
Form SA106 (Foreign Income)
If you receive any income from outside the UK – even a small amount of interest from a US bank account or rental income from an overseas property – the main Self Assessment return (SA100) on its own isn’t enough.
You’ll also need to complete Form SA106, which is an additional section of Form SA106 used to report foreign income and claim any relevant tax relief.
FIG Relief Nominations
If you’re claiming the new four-year Foreign Income and Gains (FIG) regime, SA106 is also where you must now specify which foreign income sources you’re claiming relief on.
Under the updated rules, FIG relief is no longer automatic across all foreign income – it must be applied source by source.
Note: The claim must be made by January 31st in the second tax year after the year concerned. For example, for the 2025/26 tax year, the deadline to claim is January 31st 2028.
Foreign Tax Credit Relief (FTCR)
To avoid being taxed twice on the same income, you must claim Foreign Tax Credit Relief on this form. There’s a specific section where this is done.
If you declare your overseas income but don’t claim the relief correctly, HMRC may automatically charge UK tax on the full amount – even if you’ve already paid tax in the US.
Reporting Income in Pounds Sterling
All foreign income must be converted into GBP. HMRC allows the use of appropriate and consistent exchange rates – including officially published rates (like HMRC’s monthly or annual averages) or other reasonable, consistently applied exchange rates.
Using the wrong rate often leads to HMRC queries and corrections.
Need a Hand With Your UK Self Assessment?
The Expat Taxes UK team helps expats handle their Self Assessment tax return. This includes everything from registering with HMRC to fill in paperwork, reporting overseas income, and claiming the reliefs and benefits you’re eligible for.
Whether this is your first UK tax return or you just want peace of mind that it’s all done properly, we’re here with the expert tax tips and insights you need. We’re proud to work with expats from all over the world, including the US, Australia, European countries, and beyond.
Book a consultation with our team with your trusted expat tax specialists today.
P.S. By booking a consultation, you’ll receive a £100 credit that can be applied to any future services – including UK tax return preparation – so you can start saving straight away.
DISCLAIMER: The material in this article is for general information purposes only and does not constitute legal or taxation advice. Legal, financial, investment and taxation advice should be sought before acting or refraining from acting. All information and taxation rules are subject to change without notice. Expattaxes.co.uk Limited accept no liability for any action taken based on the information in this article or any of the articles on this website.
