A Reddit user recently posted in a state of genuine panic: they’d moved back to the UK three years ago, kept their Latvian sole trader business running with a single client, paid 25% tax in Latvia on that income — and never declared it to HMRC. “I’m terrified of anything legal like this and I don’t want to go to prison,” they wrote. “I just can’t believe I didn’t know I had to declare it.”
If you’re in a similar situation — UK resident, earning self-employment income from a business registered abroad, and you didn’t realise you had to tell HMRC — take a breath. This is fixable, the amounts involved are often small, and you are not going to prison. But you do need to act, and the way you act matters. Here’s what the rules actually say, what the Reddit advice got wrong, and exactly what to do.
The Core Rule: UK Tax Resident = Worldwide Income
If you’re UK tax resident, you’re taxed on your worldwide income — not just what you earn in the UK. This is confirmed in HMRC’s HS211 helpsheet:
“UK residents are ordinarily taxable on their worldwide income.”
It doesn’t matter that:
- The business is registered abroad (Latvia, or anywhere else)
- The client is abroad
- The money goes to a foreign bank account
- You already paid tax in that country
If you live and work in the UK, and you’re UK tax resident, that income is taxable in the UK. The fact that you paid tax abroad doesn’t exempt you from declaring it here — it means you can claim relief so you don’t pay tax twice (more on that below).
How do I know if I’m UK tax resident?
You’re automatically UK tax resident if you spend 183 or more days in the UK in a tax year (6 April to 5 April). There are additional tests in the Statutory Residence Test that consider your ties to the UK (family, accommodation, work, and previous residence). If you’ve been living and working in the UK for three years, you are almost certainly UK tax resident.
“But I Already Paid Tax Abroad” — Why That’s Not the End of It
This is the most common misconception, and it’s understandable. You paid 25% tax in Latvia. Why should HMRC get a look in?
The answer is that the UK and Latvia have a Double Taxation Agreement (DTA) — a treaty designed to prevent the same income being taxed twice. But DTAs work by allocating taxing rights and providing relief, not by making the income disappear from the UK tax system entirely.
Here’s how it works in practice:
- You declare the foreign income on your UK Self Assessment.
- You calculate the UK tax due on it.
- You claim Foreign Tax Credit Relief (FTCR) for the tax you already paid abroad.
- HMRC reduces your UK tax bill by the amount of foreign tax paid (up to the UK tax due on that income).
If the foreign tax rate is higher than the UK rate, you get no UK tax bill on that income (but you can’t reclaim the excess from HMRC). If the foreign rate is lower, you pay the difference to HMRC. Either way, you don’t pay tax twice — but you do have to declare it and do the calculation.
The DTA might mean the other country shouldn’t have taxed you at all
Here’s a subtlety the Reddit thread completely missed. Under the UK-Latvia Double Taxation Convention, Article 7 (Business Profits) says:
“The profits of an enterprise of a Contracting State shall be taxable only in that State unless the enterprise carries on business in the other Contracting State through a permanent establishment situated therein.”
And Article 14 (Independent Personal Services) — per HMRC’s Double Taxation Relief Manual — says income from professional services is taxable only in the UK unless you have a “fixed base regularly available” in Latvia.
So if you’re a UK resident doing graphic design from your laptop in the UK, with no office or fixed base in Latvia, the DTA may allocate the taxing rights to the UK alone. This means the 25% Latvian tax you paid might not have been due under the treaty at all — and HMRC may not give you full Foreign Tax Credit Relief for tax that wasn’t properly chargeable under the DTA.
This is exactly the kind of cross-border complexity where you need a professional. It’s not a reason to panic — it’s a reason to get someone who understands DTAs to look at your specific situation.
Where to Declare It: The Detail Nobody Explains
This is the bit that catches people out even after they realise they need to declare foreign income. There are two relevant sets of pages on a Self Assessment return, and foreign self-employment income goes on the wrong one if you’re not careful.
The SA106 Foreign pages notes are explicit:
“Do not use the ‘Foreign’ pages for foreign income earned by a trade or partnership — use the ‘Self-employment’ or ‘Partnership’ pages instead.”
So:
- Foreign self-employment income → declare on the Self-employment pages (SA103), just like UK self-employment income
- Foreign Tax Credit Relief → claim on the Foreign pages (SA106), in the section for “foreign tax paid on employment, self-employment and other income”
- Foreign employment income → declare on the Employment pages (SA102), then claim FTCR on the Foreign pages
- Foreign savings interest, dividends, pension income → declare on the Foreign pages (SA106) directly
If you put self-employment income on the Foreign pages, HMRC may process it incorrectly or ask you to amend. Get this right the first time.
The Penalty Reality: Why Coming Forward First Matters
This is where the Reddit thread was vague, and where understanding the rules could save you serious money.
Offshore non-compliance — which includes failing to declare foreign income — carries higher penalties than onshore mistakes. According to the HMRC compliance handbook, the standard penalty for offshore failures is 200% of the tax due. That’s not a typo — double the tax you owe.
But that 200% can be reduced based on two things:
1. Whether the disclosure was voluntary
| Disclosure type | Minimum penalty | Maximum penalty |
|---|---|---|
| Voluntary (you come forward before HMRC contacts you) | 100% of tax due | 200% of tax due |
| Non-voluntary (HMRC contacts you first) | 150% of tax due | 200% of tax due |
The difference between 100% and 150% is enormous. If you owe £500 in tax, voluntary disclosure means a penalty between £500 and £1,000. If HMRC finds you first, it’s between £750 and £1,000. And that’s before considering that HMRC may be less generous with quality-of-disclosure reductions when they had to find the problem themselves.
2. The quality of your disclosure
HMRC reduces the penalty further based on how helpful you are:
- Telling — you tell HMRC about the non-compliance and explain what happened
- Helping — you give HMRC reasonable help to quantify the underpayment (providing records, bank statements, etc.)
- Giving access — you allow HMRC to check your records
A full, honest, well-documented voluntary disclosure gets you to the bottom of the range. A grudging, incomplete disclosure after HMRC sends you a letter gets you to the top.
What this means for you
If you’ve read this far and you haven’t been contacted by HMRC: you are in the voluntary disclosure window. This is the best position you can be in. Coming forward now, before HMRC discovers the issue (and with automatic exchange of information between tax authorities, they increasingly do), gets you the lowest possible penalties.
How Far Back Can HMRC Go?
A Reddit commenter suggested filing returns “for the last 20 years.” That’s misleading and unnecessarily terrifying. Here are the actual time limits:
| Type of non-compliance | Assessment time limit |
|---|---|
| Normal (onshore, no negligence) | 4 years |
| Negligent (onshore) | 6 years |
| Offshore, non-deliberate | 12 years |
| Offshore, deliberate | 20 years |
The 12-year offshore limit was introduced by a 2021 measure extending offshore time limits — it increased the previous 4/6 year limits for non-deliberate offshore matters to 12 years. The 20-year limit applies only where the non-compliance was deliberate — i.e., you knew you should declare it and chose not to.
For the Reddit poster — 3 years of small income, genuine ignorance — this is a non-issue. They need to file for the 3 years they had the income while UK resident. The 20-year figure is for deliberate evaders, not people who didn’t know.
The Good News: You Probably Owe Very Little
The Reddit poster mentioned their total income over 3 years was “barely £4,000.” Here’s why that matters:
The £1,000 trading allowance
Every UK taxpayer gets a £1,000 trading allowance per tax year — tax-free, no need to declare if your total trading income is £1,000 or under. According to HMRC’s guidance on tax-free allowances, this applies to self-employment income regardless of where the trade is carried on.
If your foreign self-employment income is £1,000/year or less, you may not need to declare it at all (though there are exceptions — see the guidance). If it’s above £1,000, you can choose to deduct the £1,000 allowance instead of actual expenses.
The £12,570 Personal Allowance
Every UK taxpayer also gets a Personal Allowance of £12,570 — income up to that amount is tax-free. If your foreign self-employment income is your only income (or your total income including UK employment is below £100,000), the Personal Allowance applies to it.
So someone earning ~£1,300/year from a Latvian sole trader business, with a UK 9-to-5 job that uses up most of their Personal Allowance, would owe UK tax on roughly £300/year (after the £1,000 trading allowance) at 20% — that’s £60/year. Over 3 years, that’s £180 in tax. Penalties at the voluntary minimum (100%) would add £180. Total exposure: around £360.
That’s not nothing, but it’s not “thousands of pounds” and it’s certainly not prison.
Foreign Tax Credit Relief
If the DTA allows Latvia to tax the income (which, as noted above, it may not for someone working from the UK with no fixed base there), you can claim Foreign Tax Credit Relief for the 25% Latvian tax already paid. This would reduce or eliminate the UK tax due — though if the DTA says only the UK should tax it, the situation is more complex and the Latvian tax may need to be reclaimed from Latvia, not credited against UK tax.
Again, this is where a professional earns their fee.
What to Do: Step by Step
Step 1: Gather your records
For each tax year you’ve had the foreign income:
- Bank statements (foreign and UK)
- Invoices or records of what you earned
- Proof of tax paid abroad (Latvian tax returns, payment confirmations)
- Any expenses related to the self-employment
Step 2: Register for Self Assessment
If you’re not already registered, register for Self Assessment with HMRC. You’ll need to do this by 5 October after the tax year you need to report. If you’re filing for missed years, register now — don’t wait.
Step 3: File the missed returns
File Self Assessment returns for each year you had undeclared foreign income. On each return:
- Declare the self-employment income on the Self-employment pages (SA103)
- Claim the £1,000 trading allowance (or deduct actual expenses if higher)
- Claim Foreign Tax Credit Relief on the Foreign pages (SA106) for tax paid abroad
- Include a note in the “Any other information” box explaining that you’re voluntarily disclosing previously undeclared foreign income and why it wasn’t declared (genuine ignorance of the worldwide income rule)
Step 4: Pay what you owe
Once HMRC processes the returns, they’ll tell you the tax due plus any penalties. Pay it promptly — late payment adds interest and further penalties on top.
Step 5: Consider whether to keep the foreign business
If you’re doing all the work from the UK, you may want to:
- Deregister the sole trader business abroad (to stop paying tax there unnecessarily)
- Register as a sole trader in the UK instead (simpler, and aligns with where the work is actually done)
This is a decision to make with an accountant, as it has implications in both countries. If you’re receiving or converting foreign currency while you restructure, Wise is a practical multi-currency business account for that.
Should You Do This Yourself or Get Help?
For simple, small-amount cases, you can do this yourself. But for offshore matters specifically, we strongly recommend getting professional help. Here’s why:
- The penalty regime is harsher. Offshore penalties start at 100% minimum (voluntary) versus much lower onshore equivalents. A mistake in how you disclose could cost you.
- The DTA analysis is not simple. Whether the other country should have been taxing you at all, whether you can claim full FTCR, and whether you should reclaim foreign tax — these are treaty interpretation questions.
- HMRC takes offshore matters more seriously. Automatic exchange of information means HMRC is increasingly finding foreign income before taxpayers declare it. Coming forward correctly, with the right framing, matters.
- The amounts at stake may be larger than they appear. What seems like “barely £4,000” can trigger penalties, interest, and complications that compound.
Free help if you can’t afford an accountant
If your income is low and you can’t afford an accountant, contact TaxAid — a charity providing free tax advice to people on low incomes who can’t afford professional help. They have experience with offshore disclosure cases and can guide you through the process. The Reddit poster was right to plan on calling them.
If you can afford professional help, use our Find an Accountant service and mention that you have undeclared foreign income — we’ll match you with someone who handles offshore matters.
What Not to Do
- Don’t wait and hope HMRC doesn’t find out. Automatic exchange of information under the Common Reporting Standard means foreign financial institutions report to HMRC. The Latvian bank account is likely already visible to HMRC.
- Don’t call HMRC and confess without preparing first. A panicked phone call where you can’t provide specifics doesn’t help your case. Gather your records, understand your position, then make contact — ideally through a written disclosure or via an accountant.
- Don’t assume the 20-year limit applies to you. That’s for deliberate evasion. If this was a genuine mistake, the 12-year limit (or less) applies, and for small amounts over a few years, it’s a manageable problem.
- Don’t deregister the foreign business before sorting the UK side. Sort the declaration first, then restructure.
The Bottom Line
- UK tax residents are taxed on worldwide income. Foreign self-employment income must be declared to HMRC, even if you’ve already paid tax abroad.
- You declare it on the Self-employment pages (SA103), not the Foreign pages. Claim Foreign Tax Credit Relief on SA106 for tax already paid abroad.
- The DTA may mean the other country shouldn’t have taxed you at all — if you were working from the UK with no fixed base abroad. This needs professional review.
- Offshore penalties are 100%–200% of tax due, but the minimum (100%) applies if you come forward voluntarily before HMRC contacts you. This is the single most important thing to understand.
- You’re not going to prison. Criminal prosecution is for deliberate, large-scale evasion. An honest mistake with small amounts, voluntarily disclosed, results in back tax plus a penalty — not a criminal record.
- Get help. Offshore matters are the one area where DIY is genuinely risky. Use TaxAid if you can’t afford an accountant, or find an accountant who handles offshore disclosures if you can.
For the full list of HMRC contact types, investigations, and what to do when HMRC contacts you, see our HMRC contacted me hub.
If you’re also dealing with late filing penalties on top of undeclared income, see our guide on how to appeal an HMRC penalty. For the full overview of what happens during an HMRC investigation — the 3 tiers of scrutiny, the enquiry stages, COP9, and when to get professional representation — see our HMRC investigation hub. For help understanding Self Assessment basics, browse our jargon buster.