UK Self Assessment Tax Return: Guide for Expats 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 new FIG regime that replaced the non-dom remittance basis from April 2025), and the most important deductions and reliefs available to expats.

Who Must File UK Self Assessment

You must register for and file a UK Self Assessment return if in the tax year you:

• Were self-employed with income over £1,000
• Were a company director (excluding non-executive directors of charities)
• Had income over £100,000 (even if all via PAYE)
• Had untaxed income (rental income, foreign income, savings interest above allowances)
• Were a higher-rate taxpayer who claimed pension relief beyond basic-rate
• Want to claim certain tax reliefs (gift aid above basic rate, marriage allowance, remittance basis)
• Had capital gains above the annual exempt amount (£3,000 in 2024/25)

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).

Statutory Residence Test

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.

Remittance Basis for Non-Domiciled Residents

The remittance basis was abolished from 6 April 2025 and replaced by the FIG (Foreign Income and Gains) regime. Non-domiciled UK residents can no longer elect into the remittance basis for 2025/26 onwards.

What the Remittance Basis Was (pre-April 2025)

Under the old regime, non-domiciled UK residents (those whose country of permanent domicile was outside the UK) could elect to pay UK tax only on UK-source income and foreign income/gains remitted (brought) to the UK. Foreign income kept offshore was untaxed. Cost: free for the first 7 years of UK residency (but you lost the personal allowance and CGT annual exempt amount); Remittance Basis Charge (RBC) £30,000/year from year 7; £60,000/year from year 12. Deemed domicile rules applied after 15 years of UK residency, ending access entirely.

The Replacement: FIG Regime (from April 2025)

New UK arrivals who have not been UK tax resident in any of the prior 10 years can elect into the FIG regime:

• 0% UK tax on all foreign income and gains for the first 4 years of UK tax residency
• No remittance condition — foreign income can be brought to the UK freely without triggering UK tax
• Personal allowance is retained (unlike the old remittance basis for longer-term residents)
• After 4 years, worldwide income is fully subject to UK income tax on the arising basis

Temporary Repatriation Facility (TRF)

For those who were using the remittance basis before April 2025 and accumulated offshore foreign income or gains: the TRF allows that pre-April 2025 foreign income and gains to be remitted to the UK at a 12% tax rate in 2025/26 and 2026/27 (rising to 15% in 2027/28). After the TRF window closes, normal income tax rates apply to any subsequent remittances of pre-April 2025 offshore income.

Foreign Income on a UK Self Assessment Return

How different types of foreign income are taxed:

Foreign Employment Income

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.

Foreign Rental Income

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.

Foreign Dividends and Interest

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.

Claiming Double Tax Treaty Relief

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.