Missed foreign income on your tax return? How to put it right

If foreign income or gains should have been reported to HMRC but were missed, work out the affected tax years and correct the position rather than simply adding the income to the next return. The route can be an amendment, late returns or a formal disclosure depending on how old the issue is and whether HMRC has already contacted you.

Foreign income is also an area where the tax rules changed materially from 6 April 2025, so older and newer years may need different analysis.

What counts as foreign income?

Examples include:

• salary or freelance income from overseas;
• foreign bank interest;
• foreign dividends;
• rent from overseas property;
• overseas pensions;
• income from foreign investments;
• certain distributions from overseas entities.

Capital gains on foreign assets can also be relevant, but gains and income are not the same tax category.

The Channel Islands and Isle of Man are foreign for these purposes.

UK residence comes first

Whether foreign income is taxable in the UK depends heavily on UK tax residence and the rules applying for the year.

A UK resident will normally be taxable on foreign income, subject to reliefs and exceptions. A non-UK resident is generally not taxed by the UK on foreign income, although UK-source income can still remain taxable.

Do not assume residence is decided simply by where you own a home or where you spend “most of the year”. The Statutory Residence Test can require a detailed day-count and ties analysis.

The rules changed from 6 April 2025

For years from 6 April 2025, the UK's Foreign Income and Gains (FIG) regime replaced the old remittance-basis framework for new qualifying claims.

That means an old article about “non-doms” or the remittance basis may be the wrong starting point for 2025 to 2026 or later.

If the issue spans several years, classify each year separately:

• pre-6 April 2025 years may involve the old residence/remittance-basis rules;
• 2025 to 2026 onward may involve the FIG regime where the eligibility conditions are met.

If you have not filed the return at all

First establish which returns HMRC expects.

For each year, gather:

1. UK residence status;
2. UK income;
3. foreign income by country and type;
4. foreign tax paid;
5. capital gains if relevant;
6. previous HMRC correspondence;
7. whether a return was issued or registered.

Then prepare the correct return for each year rather than compressing several years into one number.

If you filed but left the foreign income out

If the return can still be amended using the normal Self Assessment amendment process, that may be the simplest route.

If it is too old for a normal amendment, HMRC's disclosure procedures may be relevant. GOV.UK specifically tells taxpayers to come forward as soon as possible when taxable income has not been declared.

For offshore matters, HMRC may direct taxpayers to an offshore disclosure facility or the Offshore Co-ordination Unit depending on the facts.

Why voluntary disclosure matters

HMRC's guidance says that if you contact them first, they may consider the case more favourably.

That does not mean penalties disappear. The tax, interest and possible penalties still need to be calculated, and offshore non-compliance can carry more serious penalties than some domestic errors.

But there is an obvious practical difference between correcting a mistake voluntarily and waiting until HMRC has already identified it.

What if tax was already paid overseas?

Do not omit the income merely because another country taxed it.

If the income is taxable and reportable in the UK, it normally still goes on the UK return. You may be able to claim Foreign Tax Credit Relief for qualifying foreign tax so that the same income is not taxed twice without relief.

The correct relief can depend on:

• the country;
• the type of income;
• the relevant double-tax treaty;
• the amount of foreign tax;
• UK tax attributable to the same income.

Which Self Assessment pages are used?

Foreign income and gains are commonly reported using the SA106 Foreign supplementary pages with the SA100 tax return.

Residence and certain FIG claims can require the SA109 residence/FIG pages and additional calculations or helpsheets.

The form is the final output. The harder work is correctly classifying the income and the residence/relief position before filling it in.

Example: late return plus foreign bank interest

Suppose a UK resident filed no return for a year in which they had taxable foreign bank interest.

The sensible sequence is:

1. confirm the tax year and residence status;
2. total the foreign interest in sterling using an appropriate exchange basis;
3. identify any foreign tax deducted;
4. establish the UK tax treatment for that year;
5. prepare the missing return;
6. calculate tax, interest and any penalty exposure;
7. file or disclose through the appropriate HMRC route.

Do not simply include the old interest in the current year's savings figure.

What if HMRC has already written to you?

Treat that as more urgent.

The correct response depends on whether the letter is:

• a generic nudge letter;
• a request to check overseas tax affairs;
• a formal compliance check;
• a discovery assessment or penalty notice.

The response route and deadlines can be different. Keep the envelope, letter date and any response deadline.

What to gather before asking for help

For an adviser to assess a foreign-income disclosure efficiently, prepare:

• countries involved;
• income type and amount by tax year;
• dates you arrived in or left the UK;
• days spent in the UK for relevant years;
• foreign tax returns or assessments;
• bank, broker or pension statements;
• foreign tax paid;
• previous UK returns;
• any HMRC letters;
• whether the money was remitted to the UK for pre-2025 years where that can matter.

Foreign tax problems become expensive when several different questions are mixed together. Separating residence → income → year → foreign tax → reporting status usually makes the position much clearer.