If you’re a UK expat living in Portugal, there’s a good chance you’ve had a mild panic attack wondering whether you’ll end up paying tax on the same income in both countries. It’s one of the most common questions I hear from clients: “Am I going to be taxed twice on my pension?” The short answer is no — and the reason is the double taxation agreement between the UK and Portugal.

This agreement (formally known as a double taxation convention, or DTC) is essentially a deal between the two countries that prevents you from being taxed on the same income by both HMRC and the Portuguese tax authority. It’s been in place since 1968, updated over the years, and it covers everything from pension income to rental property, dividends, and capital gains. Understanding how it works isn’t just useful — it’s essential for making smart financial decisions as an expat.

In this guide, I’ll walk you through exactly what the agreement covers, how it applies to the most common types of income UK expats in Portugal have, and the practical steps you need to take to make sure you’re not overpaying tax anywhere.

What Is a Double Taxation Agreement and Why Does It Matter?

A double taxation agreement (DTA) is a treaty between two countries that sets out which country has the right to tax specific types of income. Without one, you could theoretically be liable for tax on the same income in both your country of residence and your country of origin.

For UK expats in Portugal, this matters enormously. As a Portuguese tax resident, Portugal generally wants to tax your worldwide income. Meanwhile, the UK may still want to tax certain income that originates there — your UK pension, rental income from a property you still own in Manchester, or dividends from UK shares.

The UK-Portugal DTA resolves this by assigning taxing rights. For each type of income, the treaty specifies whether it should be taxed in the country where it arises (the “source” country, usually the UK) or the country where you live (the “residence” country, Portugal). In some cases, both countries can tax the income, but you’ll receive a tax credit to ensure you don’t pay more than the higher of the two rates.

The current agreement between the UK and Portugal is based on the OECD Model Tax Convention, which most international tax treaties follow. It’s publicly available on HMRC’s website, though I’d recommend having a cup of strong Portuguese coffee before attempting to read it in full.

How the DTA Applies to UK Pensions

Pensions are the big one for most of my clients, and rightly so. If you’ve spent 30 years building up a UK pension and you’ve now retired to the Algarve, you want to know exactly where and how that income will be taxed.

Under the UK-Portugal DTA, private pensions (including SIPPs, personal pensions, and occupational pensions) are generally taxable only in your country of residence. So if you’re a Portuguese tax resident drawing income from a UK SIPP, that income is taxable in Portugal, not the UK.

This is where the NT (No Tax) code comes in. You can apply to HMRC for an NT tax code, which instructs your UK pension provider to pay your pension gross — without deducting UK tax. You’ll then declare the income on your Portuguese tax return and pay Portuguese income tax on it instead. I’ve written a detailed guide on claiming the NT tax code if you want the step-by-step process.

There’s an important exception: UK government pensions (civil service, NHS, teachers, police, military) are treated differently. Under Article 19 of most DTAs, government service pensions remain taxable in the UK. So if you receive a civil service pension, the UK retains the right to tax it regardless of where you live. However, Portugal may also tax it under domestic law, and you’d receive a credit for the UK tax already paid. In practice, this means you typically only pay the higher of the two rates.

The UK State Pension is taxable in Portugal as your country of residence, following the same rules as private pensions. You can request gross payment from the DWP by completing the necessary HMRC forms.

Property Income: UK Rental Properties

Many expats in Portugal still own property back in the UK — perhaps a buy-to-let they kept when they moved, or a family home they’re renting out while they decide what to do with it. The DTA has clear rules on how this is taxed.

Under Article 6 of the treaty, rental income from property can be taxed in the country where the property is situated. This means the UK has the right to tax rental income from your UK property, even though you live in Portugal. You’ll need to complete a Self Assessment tax return in the UK and pay UK income tax on the net rental profit.

However, as a Portuguese tax resident, you’re also required to declare this worldwide income in Portugal. The DTA prevents double taxation by giving you a tax credit in Portugal for the UK tax you’ve already paid. So if you paid 20% tax in the UK and Portugal’s rate on that income works out at 28%, you’d only pay the additional 8% difference to Portugal.

In my experience, the property income situation catches people out more than any other. I’ve had clients who assumed that because they were paying UK tax on their rental income, they didn’t need to declare it in Portugal at all. That’s not the case — you must declare it, and then claim the credit. Getting this wrong can result in penalties from the Portuguese tax authority.

Dividends, Interest, and Investment Income

If you hold UK investments — shares paying dividends, bonds generating interest, or funds producing capital gains — the DTA sets out specific rules for each.

Dividends from UK companies can be taxed in both countries under the treaty, but the UK’s withholding tax on dividends paid to Portuguese residents is capped at 10% (or 15% in some cases). Portugal then taxes the dividend income at its domestic rate, but gives you a credit for the UK tax withheld. For most expats, dividends are taxed at a flat 28% in Portugal, so after the UK credit, you’d pay the balance to Portugal.

Interest income follows a similar pattern. The UK can withhold tax at source (typically capped at 10% under the treaty), and Portugal taxes it at 28%, with a credit for the UK amount. In practice, many UK savings accounts now pay interest gross to non-UK residents, so you may find there’s no UK tax to credit — you simply pay Portuguese tax on the full amount.

Capital gains on investments (shares, funds, etc.) are generally taxable only in the country of residence under the DTA. So if you sell UK shares at a profit while living in Portugal, the gain is taxable in Portugal, not the UK. The exception is gains on UK property, which can be taxed in the UK (and you’d claim a credit in Portugal as with rental income).

If you hold investments in a tax-efficient structure such as a portfolio bond or international investment wrapper, the tax treatment may differ. These structures can defer tax on underlying gains and income, which can be particularly advantageous when combined with the DTA provisions. It’s worth getting professional advice on how your specific investment arrangement interacts with the treaty.

Self-Employment and Business Income

More and more expats are running businesses or freelancing remotely from Portugal. If you’re self-employed and earning income from UK clients, the DTA determines where that income is taxed.

Under the business profits article, if you’re a Portuguese tax resident running a business without a “permanent establishment” in the UK (essentially, you don’t have a fixed office or base of operations there), your business profits are taxable only in Portugal. This is good news for digital nomads and remote workers — your UK client income is taxed in Portugal, not the UK.

If you do maintain a permanent establishment in the UK (an office, a warehouse, a branch), the profits attributable to that establishment can be taxed in the UK, with a credit available in Portugal. The definition of “permanent establishment” is quite specific and technical, so if you’re in any doubt, it’s worth getting advice on your particular setup.

How to Claim Treaty Benefits: The Practical Steps

The DTA doesn’t apply automatically — you need to take active steps to claim the benefits. Here’s what that looks like in practice:

For pension income: Apply to HMRC for the NT tax code using form DT-Individual (or the online equivalent). You’ll need to provide evidence of your Portuguese tax residency, which your local Finanças office can provide. Once approved, HMRC will issue the NT code to your pension provider, and your pension will be paid gross. This can take several weeks, so apply as early as possible.

For rental income: File a UK Self Assessment return declaring your rental income and pay UK tax as normal. Then declare the same income on your Portuguese Modelo 3 tax return, claiming a credit for the UK tax paid under the “Anexo J” (foreign income annex). Keep your UK tax calculation and payment receipts as evidence.

For investment income: Ensure your UK investment platform knows you’re a Portuguese tax resident so they can apply the correct withholding rates under the treaty. Declare all investment income on your Portuguese tax return with appropriate credits.

For all income types: Obtain a Certificate of Tax Residence from the Portuguese tax authority each year. This document proves to HMRC (and other UK payers) that you’re entitled to treaty benefits. You can request this through your local Finanças office or via the Portal das Finanças online.

Common Mistakes Expats Make with the DTA

In my years of advising UK expats in Portugal, I’ve seen the same mistakes crop up again and again. Here are the ones that cost people the most:

Not declaring worldwide income in Portugal. Just because income is taxed in the UK doesn’t mean you can ignore it in Portugal. You must declare your worldwide income and claim the appropriate credits. The Portuguese tax authority has information-sharing agreements with HMRC, and discrepancies will eventually surface.

Failing to apply for the NT code. If you’re having UK tax deducted from your pension unnecessarily, you’re effectively lending money to HMRC interest-free while also paying Portuguese tax. Apply for the NT code as soon as you become Portuguese tax resident.

Assuming the DTA eliminates all tax. The treaty prevents double taxation, but it doesn’t eliminate taxation altogether. You’ll still pay tax — the question is where and at what rate. Sometimes the Portuguese rate is higher than the UK rate, and sometimes it’s lower. The DTA ensures fairness, not a tax holiday.

Not keeping proper records. You need documentation showing what tax you’ve paid in each country to claim credits. Keep your HMRC tax calculations, P60s, dividend vouchers, and Portuguese tax returns in order. Your future self (and your accountant) will thank you.

Frequently Asked Questions

Does the double taxation agreement mean I won’t pay any tax?

No. The DTA prevents you from paying tax twice on the same income, but you’ll still pay tax in at least one country. It determines which country has the primary right to tax each type of income, and provides credits where both countries have taxing rights.

Do I need to do anything to benefit from the DTA, or is it automatic?

You need to take active steps. For pension income, apply to HMRC for the NT tax code. For other income, declare it properly on both your UK and Portuguese tax returns and claim the appropriate credits. The treaty doesn’t apply itself — you need to invoke it.

What if I’m taxed in both countries by mistake?

If you’ve been double-taxed, you can claim a refund. In the UK, contact HMRC with evidence of Portuguese tax paid on the same income. You can also raise a claim through the “mutual agreement procedure” outlined in the DTA, though this is a last resort as it can be slow.

Does the DTA apply to the UK State Pension?

Yes. The UK State Pension is treated as a private pension under the DTA and is taxable in Portugal as your country of residence. You can arrange for it to be paid without UK tax deducted by notifying HMRC of your Portuguese tax residency.

Has Brexit affected the double taxation agreement?

No. Double taxation agreements are bilateral treaties between countries, not EU agreements. The UK-Portugal DTA remains fully in force and has not been affected by Brexit. Your treaty protections are unchanged.

What to Do Next

The UK-Portugal double taxation agreement is one of the most important financial protections you have as a British expat. Understanding how it applies to your specific income — pensions, property, investments, or business earnings — can save you significant money and stress. The key is being proactive: claim the reliefs you’re entitled to, declare your income correctly in both countries, and keep proper documentation.

If you’d like to discuss how the double taxation agreement applies to your personal situation, get in touch with our team. We specialise in helping UK expats in Portugal make the most of their pensions and investments, and we deal with cross-border tax issues every day.

Matthew Renier is a Chartered Financial Adviser at Arthur Browns Wealth Management, based in the Algarve, Portugal. He has over 15 years of experience helping British expats manage their pensions and financial planning across borders.

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