Expat Self Assessment: Filing a UK Tax Return When You Live Abroad

Yes, you may still need to file a UK Self Assessment tax return even when you live abroad, because UK Income Tax and Capital Gains Tax follow the source of certain income and gains, not only where you live. Being non-resident reduces the scope of what the UK can tax, but it rarely removes the obligation to report UK-source income altogether.

As a general rule, a non-resident is taxable in the UK on UK-source income (such as UK rental profit, certain UK employment duties, and some UK pensions) and on gains from UK land and property. Most genuinely foreign income and gains fall outside the UK net once you are non-resident. The question of whether you are resident at all is decided by the Statutory Residence Test, which counts your days in the UK and weighs your ties to the country. If you are unsure of your status, settle that first, because it drives everything else on the return.

A common myth is that paying tax in your new country of residence means there is nothing to do in the UK. That is not how it works. The UK can still tax UK-source income; you then use double taxation relief (covered below) to make sure the same income is not taxed twice. The reporting still has to happen.

To file an expat Self Assessment return you must first be registered with HMRC and hold a Unique Taxpayer Reference (UTR), and the deadline to register is 5 October following the end of the tax year in which the income or gain first arose. For example, if you first received UK rental profit in the 2024/25 tax year, you should have registered by 5 October 2025.

If you have never been in UK Self Assessment before and you are not self-employed, you normally register using form SA1. You can do this either online or by post, and HMRC treats a UK National Insurance number as optional on the form, so you can still register if you do not have one. Once registered, HMRC sets up a Self Assessment record and issues your UTR, which can take a few weeks to arrive and is usually slower for applicants who live abroad, so leave plenty of time before the filing deadline.

Non-resident landlords have an additional, separate step. Before you receive rent gross, you (or your tenant or letting agent) apply under the Non-Resident Landlord Scheme using form NRL1 so that UK tax is not deducted at source from your rent. Approval does not exempt the income; it simply moves the tax into your annual Self Assessment rather than having it withheld. Registering for the scheme and registering for Self Assessment are two different things, and you may need both.

A practical complication for expats is that you usually need a Government Gateway account to file, and verifying your identity from outside the UK can be awkward without UK-issued documents. Building in time for registration, UTR issue, and account setup is the single biggest favour you can do yourself.

An expat return is built from the main SA100 tax return plus whichever supplementary pages match your income, and for non-residents the SA109 residence pages are almost always essential. Getting the right combination of pages is what separates a clean filing from one that triggers HMRC queries.

• SA100, the main tax return. This is the core form everyone completes, summarising your income, gains, allowances, and the tax position.
• SA105, UK property pages. Used to report UK rental income and expenses, including for non-resident landlords. Most expats with UK lets need this.
• SA109, residence and FIG regime pages. Used to declare your residence status, claim split-year treatment, claim the personal allowance as a non-resident where you are entitled, and make claims under the new Foreign Income and Gains regime where relevant.
• SA106, foreign pages. Used to report foreign income that remains UK-taxable and, importantly, to claim Foreign Tax Credit Relief for tax already paid abroad.
• SA108, capital gains pages, where you have gains to report beyond the separate 60-day property reporting.

The SA109 is the form expats most often miss, and leaving it out is a serious problem. Without it, HMRC has no way to know you are non-resident or claiming split-year treatment, so the return is processed as if you were a full-year UK resident. That can mean UK tax charged on income that should be outside scope, or the personal allowance applied incorrectly. If you are non-resident for any part of the year, plan around the SA109 from the start.

Your residence status, any split-year treatment, and (for new UK arrivers) the Foreign Income and Gains regime are all declared on the SA109 residence pages, and from 6 April 2025 the rules here changed significantly. The old remittance basis for non-doms was abolished and replaced by the FIG regime, so anyone advising on the basis of the previous regime is working from outdated rules.

Split-year treatment is the key concept for the year you actually move. In the tax year you leave or arrive, the UK can treat the year as split into a UK part and an overseas part, so that your foreign income and gains in the overseas part are not taxed in the UK. You claim split-year treatment on the SA109 and must meet one of the specific statutory cases for it to apply. This is one of the most valuable, and most misapplied, parts of an expat return.

For people moving to the UK rather than away from it, the headline change is the Foreign Income and Gains (FIG) regime. From 6 April 2025, an individual who becomes UK resident and is still within their first four years of UK tax residence, following at least a 10-year period of non-UK residence, can claim, for those qualifying years, not to pay UK tax on qualifying foreign income and gains, whether or not those funds are brought to the UK. A claim is made on the Self Assessment return for each year you want it, and claiming has a cost: for any year you claim, you give up your tax-free personal allowance and the capital gains annual exempt amount (and, if otherwise eligible, the Married Couple's Allowance, Marriage Allowance and Blind Person's Allowance). The deadline to claim for a given year is the first anniversary of the 31 January filing deadline for that year, so for 2025/26 the claim must be made by 31 January 2028.

Because residence, split-year, and FIG claims interact with double taxation treaties and with the loss of allowances, this is the section where mistakes are most expensive. It is worth modelling the numbers before you decide whether to make a FIG claim at all.

Double taxation relief stops the same income being taxed in full in two countries, and you claim it on your UK Self Assessment return either under a double taxation agreement or as Foreign Tax Credit Relief. The two routes overlap but are not identical, and choosing the right one matters.

The UK has double taxation agreements (DTAs) with most countries. A treaty can give one country the sole right to tax a particular type of income, or it can cap the tax rate, or it can require one country to give credit for tax paid in the other. As a non-resident, you may be able to claim full or partial relief from UK tax on UK income where the treaty assigns taxing rights to your country of residence. To support a treaty claim, HMRC will usually expect a Tax Residency Certificate from your country of residence confirming you are tax resident there.

Foreign Tax Credit Relief (FTCR) works differently. Where income remains taxable in both countries, FTCR lets you set the foreign tax already paid against your UK tax on the same income, up to the amount of UK tax due on that income. You claim FTCR on the SA106 foreign pages, and you should keep evidence of the foreign tax actually paid, because HMRC can ask for it. The relief is limited to the lower of the UK tax and the foreign tax on that income, so it removes double taxation rather than refunding foreign tax in excess of the UK charge.

A non-resident's entitlement to the UK personal allowance also feeds into this. You normally only keep the personal allowance as a non-resident if you are a UK national, an EEA national, a resident of the Channel Islands or Isle of Man, or covered by a specific treaty provision. Where you are entitled, you claim it on the SA109. Getting the allowance and the relief claims to work together is fiddly, and it is a frequent source of overpaid UK tax that goes unclaimed.

Most non-residents cannot file their expat return through HMRC's free online Self Assessment service because that service does not support the SA109 residence pages. Since the SA109 is exactly the form a non-resident needs, the free route is effectively closed for the people who most often have a cross-border return.

That leaves two practical options. The first is to file on paper, posting the SA100 with all relevant supplementary pages including the SA109. The catch is the earlier deadline: paper returns are due by 31 October rather than 31 January, so the paper route costs you three months. The second option is to file online using HMRC-recognised commercial software that does support the SA109. This keeps the later 31 January online deadline and is how most expat returns are filed in practice.

This is a genuine trap for the unwary. Many expats log in to HMRC online in January, complete most of the return, then discover there is nowhere to declare their non-residence or claim split-year treatment, with the paper deadline long gone. Knowing in advance that you need software (or an agent who uses it) avoids a last-minute scramble and a missed deadline.

At Horizon UK Tax Solutions we file expat returns through professional software as standard, so the SA109 and treaty claims are handled correctly and you keep the later online deadline. It is part of our fixed-fee cross-border service rather than an extra.

The core Self Assessment deadlines are the same wherever you live: register by 5 October after the tax year ends, file on paper by 31 October or online by 31 January, and pay any tax owed by 31 January. The UK tax year runs from 6 April to 5 April, so for the 2024/25 tax year the online filing and payment deadline was 31 January 2026.

• 5 October: deadline to register for Self Assessment and obtain a UTR if you have not filed before.
• 31 October: deadline for paper returns, including those carrying the SA109 if you file on paper.
• 31 January: deadline for online returns and for paying the balancing tax for the year.
• 31 January and 31 July: payments on account dates, where you are required to make advance instalments toward the next year's bill.

Paying HMRC from overseas is straightforward but needs a little planning. You can pay by international bank transfer to HMRC, by debit card, or by other accepted methods, always quoting your UTR as the payment reference. Build in time for international transfers to clear and for any currency conversion, because the payment must reach HMRC by the deadline, not merely be sent by it. If you cannot pay in full, contact HMRC about a Time to Pay arrangement rather than simply missing the date.

Filing your expat Self Assessment return late triggers an automatic 100 pound penalty, and crucially this applies even if you owe no tax or are due a refund. Living abroad is not, by itself, a reasonable excuse, so the penalties bite expats just as hard as UK residents.

The late filing penalties escalate the longer the return is outstanding:

• Up to 3 months late: an automatic 100 pound penalty, regardless of whether tax is due.
• Over 3 months late: daily penalties of 10 pounds per day for up to 90 days, a maximum of 900 pounds, on top of the 100 pounds.
• 6 months late: a further penalty of 5 percent of the tax due or 300 pounds, whichever is greater.
• 12 months late: another 5 percent of the tax due or 300 pounds, whichever is greater, with higher charges possible in serious cases.

Late payment carries separate penalties and interest. Interest runs from the due date until the tax is paid, and percentage-based late payment penalties of 5 percent of the unpaid tax can apply at 30 days, 6 months, and 12 months. The penalties for filing and for paying are independent, so a late return that also pays late can attract both.

HMRC can cancel penalties where you have a reasonable excuse, but the bar is genuinely high and you must put things right as soon as the excuse ends. The reliable way to avoid all of this is to register early, file through software that supports the SA109, and pay with enough lead time for an international transfer to land.