Last Updated: April 2026
UK Self Assessment is the system by which individuals with income outside of PAYE (Pay As You Earn) declare their income to HMRC and calculate their tax liability. For expats living in the UK, or UK nationals returning from abroad, the Self Assessment system has particular complexity: foreign income, double taxation treaty claims, and residency determination all feed into the same return.
This guide covers who needs to file a UK Self Assessment return, the key deadlines, how foreign income is taxed (including the remittance basis for non-domiciles), and the most important deductions and reliefs available to expats.
You must register for and file a UK Self Assessment return if in the tax year you:
For expats specifically: If you are UK tax resident and received income from abroad (foreign employment income, foreign rental, foreign dividends) you must declare it on a Self Assessment return. HMRC does not receive this information automatically (though Common Reporting Standard information is increasingly shared).
The UK Statutory Residence Test (SRT) determines whether you are UK resident in any given tax year. Key rules: (1) Automatic UK resident if in the UK 183+ days in a tax year; (2) Automatic non-resident if fewer than 16 UK days (or 46 days if not UK resident in any of previous 3 years); (3) For split-year treatment (arriving or leaving mid-year), specific cases determine the date of UK residence. Getting SRT wrong is one of the most common expat tax errors — professional advice is strongly recommended for your first UK return after arriving or departing.
Non-domiciled UK residents (individuals whose country of permanent domicile is outside the UK) have access to the remittance basis — a special tax regime that limits UK taxation to UK-source income and foreign income/gains brought into the UK.
The UK announced major non-dom reform effective April 2025. The remittance basis is being replaced with a residency-based regime: a 4-year foreign income and gains (FIG) exemption for new arrivals who have been non-UK resident for 10+ years. Existing non-doms may face transitional provisions. This is a significant change — any non-dom UK resident should seek current professional advice.
How different types of foreign income are taxed:
If UK resident during a UK tax year, worldwide employment income is taxable. If also resident in the foreign country under domestic rules: treaty tie-breakers determine which country taxes; the UK return then claims a Foreign Tax Credit (FTC) for taxes paid abroad to prevent double taxation. Foreign Employment Income pages (SA106) must be completed.
Taxable on the arising basis (full remittance basis aside). Deductible expenses are similar to UK rental: mortgage interest (restricted for higher-rate), repairs, management fees, insurance. The foreign property must be declared even if running a loss — losses can be offset against future foreign property gains.
Taxable as UK dividends (above the £500 dividend allowance in 2024/25) and savings interest (above the Personal Savings Allowance). Foreign withholding tax already paid is credited, up to the treaty rate — excess foreign withholding beyond the treaty rate cannot be credited.
For income taxed both in the UK and abroad, the Self Assessment return allows a Foreign Tax Credit (SA106, boxes 13–17) for foreign taxes paid. The credit is limited to the UK tax on the same income (you cannot use excess credits from high-tax countries to reduce UK tax on UK-source income). If there is a UK tax treaty with the country, the treaty rate applies — not the domestic withholding rate.
CountryTaxCalc.com is reader-supported. When you use our partner links, we may earn a commission at no cost to you. Learn more about our affiliate partnerships
★ 4.8 Trustpilot · 1,625 reviews
US citizen living in the UK? You may need both a UK Self Assessment and a US expat return. Greenback's CPAs handle both — FEIE, Foreign Tax Credit, FBAR, and UK treaty elections done correctly.
⚠ Not the cheapest option — best for complex situations and expats who want a dedicated CPA.
UK Self Assessment + US Expat Return →★ 4.3 Trustpilot · 287,413 reviews
Paying your UK Self Assessment tax bill from overseas? Wise lets you send GBP to HMRC at the real exchange rate — no bank markup, lower fees than international wire transfers.
⚠ For currency exchange only — not a bank account replacement.
Pay HMRC from Abroad at Real Rates →The UK Self Assessment filing deadlines are: 31 October (following the 5 April tax year end) for paper returns; 31 January for online returns. So for the 2024/25 tax year (ending 5 April 2025): paper deadline 31 October 2025; online deadline 31 January 2026. Payment is also due 31 January. If you owe more than £1,000 in tax, you will also need to make Payments on Account (50% of prior year's liability) on 31 January and 31 July. Expats living abroad can register with HMRC and file online — you do not need a UK address to file, but you do need a UTR (Unique Taxpayer Reference) which you must apply for in advance.
It depends on whether you are still UK tax resident and whether you have UK-source income. If you left the UK and are non-resident: you generally do not need to file a Self Assessment return unless you have UK-source income (rental income from UK property, UK employment income, UK dividends above the allowance). UK rental income is automatically subject to UK tax regardless of residency — landlords living abroad must use the Non-Resident Landlord (NRL) scheme. If you had a capital gain on UK residential property as a non-resident: you must report within 60 days of completion using the UK Property Returns service. UK pension income is usually only taxable in the UK (check your treaty). If you departed mid-year and the UK taxes you for part of the year only (split-year treatment), you still file a Self Assessment return for that tax year.
The UK personal allowance is £12,570 for 2024/25 (frozen until 2028). UK tax residents automatically receive the personal allowance — it is offset against the first £12,570 of income. For non-residents: you only get the UK personal allowance if (1) you are an EEA national (complicated post-Brexit), (2) a British citizen or national, (3) a resident of a treaty country where the treaty provides for equal allowances. Most non-resident non-UK nationals receiving UK rental income or UK dividends will NOT receive the personal allowance. The personal allowance is also tapered for UK residents earning above £100,000: it reduces by £1 for every £2 over £100,000, creating a 60% effective marginal rate between £100,000 and £125,140. This is a major planning point for high earners — pension contributions can be used to reduce income below £100,000 and recover the full allowance.
Foreign bank account interest must be declared on the Self Assessment return (SA106 — Foreign pages). Interest earned in a foreign account is taxable UK income for UK residents. You convert the interest to GBP at the exchange rate when received (or using the HMRC average rates by tax year). Foreign withholding tax already deducted can be credited against UK income tax, up to the treaty rate with that country. Unlike the US (which requires FBAR/FATCA reporting of account balances), the UK does not currently require separate reporting of foreign bank account balances — only the income from those accounts needs to be declared. However, HMRC does receive information from overseas banks via the Common Reporting Standard (CRS), so undeclared foreign interest is increasingly detectable.
Late filing penalties: an automatic £100 penalty immediately after the 31 January deadline, regardless of whether any tax is owed. After 3 months: daily £10 penalties up to 90 days (maximum £900). After 6 months: an additional 5% of the tax due (or £300, whichever is higher). After 12 months: a further 5% of the tax due. For late payment of tax: 5% surcharge on unpaid tax after 30 days, another 5% after 6 months, another 5% after 12 months, plus daily interest (Bank of England base rate + 2.5%). If you have a reasonable excuse for late filing (serious illness, bereavement, HMRC system failure), you can appeal the automatic penalties. HMRC accepts appeals online — the standard excuse 'I didn't know I needed to file' is generally not accepted.