Last Updated on 23rd June 2026
Many expats move to Portugal under the assumption that their tax affairs will be straightforward and that what worked at home will still apply overseas. It’s often only later, and sometimes after the shock of a missed filing deadline or an unexpectedly large tax bill, that they realise that cross-border taxation doesn’t work in the same way.
Misunderstandings about double taxation, the treatment of pensions, and reporting obligations are more common than many expect. While a UK-Portugal tax treaty exists, it doesn’t apply automatically, and assuming that it does can lead to very expensive errors.
The Double Taxation Agreement (DTA) can be a valuable framework for expats, but only when it’s used correctly. Our Portuguese advisers answer some of the most common questions, highlighting where mistakes tend to arise and how to avoid them.
What Is the UK-Portugal Tax Treaty?
The DTA is a single, bilateral agreement between the two countries that sets out how income will be taxed when an individual has financial ties between the two countries, such as being a taxpayer in Portugal with UK income or being a Portuguese tax resident who owns a British property.
Replaced by a single convention in 2025, which comes into practical effect from 2026 onward, this agreement supersedes previous versions, allocates taxing rights to the UK and Portugal, establishes how tax relief is applied, and clarifies how tax residency for foreign nationals is determined.
Those implementation dates are highly relevant for expats who relocated in 2025 because changes to taxes withheld at source were only effective from 1st January 2026.
Other reforms to Corporation Tax took effect from 1st April 2026, and for UK Income Tax and Capital Gains Tax from 6th April 2026.
Why Are Tax Treaties Important for British Expats Moving to Portugal?
Tax treaties give expats a framework for understanding what their tax obligations will look like once they’ve moved, and they’re designed so that an overseas resident shouldn’t end up paying full tax twice on the same income, although this depends on the relief being correctly claimed rather than applying automatically.
While the DTA sets out which country has the right to tax different types of income, it also provides frameworks to help with:
- Determining where a person is a tax resident
- The rates of tax they’ll be required to pay
- Where different assets or incomes need to be declared
Understanding tax treaties is a key aspect of expat financial planning and helps avoid costly mistakes such as failing to report declarable assets.
How Does the UK-Portugal Tax Treaty Determine a Person’s Tax Residency Position?
Your tax residency status determines where you are primarily liable to pay tax, and in Portugal, you’ll usually be considered a tax resident if you:
- Spend 183 days+ in the country a year
- Have a permanent home or habitual residence
If there isn’t a definitive outcome, expats can use the tie-breaker rules in the DTA, which assess aspects such as where your economic and familial interests are based, such as employment, business ownership, and immediate family members.
Could an Expat Be Considered a Tax Resident in Both the UK and Portugal?
Potentially, yes, and this usually happens when expats have strong or equal ties to both countries, split their time 50/50, or have relocated mid-year.
For instance, a UK national might technically meet the criteria for British residency, while also qualifying as a Portuguese tax resident. This is where the tie-break rules we’ve mentioned come into play, as they determine the country with primary taxing rights and prevent double taxation provided the individual correctly claims against the DTA.
Existing expats who relocated before the closure of the Non-Habitual Resident (NHR) regime, or those who had planned to enrol in the regime, may benefit from personalised advice about their residency and tax positions.
For many, there are significant concerns around the transition to the new NHR 2.0 scheme, whether they will be eligible, and how their tax liabilities will change once they reach 10 years of Portuguese tax residency.
Does the UK-Portugal Tax Treaty Cover Pension Income?
Yes, the agreement provides guidance on how different types of pensions are treated and taxed.
As a rough indication, private pensions are usually taxable in Portugal for Portuguese tax residents. However, specific pension structures, such as government service schemes, may still be taxed at source in the UK.
Forthcoming changes also mean that most unused pension funds and death benefits, including those held in SIPPs, will be brought into the value of your estate for UK Inheritance Tax purposes for deaths on or after 6 April 2027, with certain exclusions such as death-in-service benefits.
For those whose NHR status is also approaching its ten-year expiry, the timing matters twice over: income that may have benefited from preferential NHR rates can face a steep increase once that status ends, in some cases rising to as much as 48% depending on income level and circumstances. Expats navigating both changes at once are advised to seek personalised advice on the available solutions after NHR expires well ahead of either deadline.
What Does the DTA Include Around Dividend, Interest and Investment Income Taxation?
Income from outside employment will typically be taxed in Portugal, since tax residents are taxed on their worldwide income, including dividends, interest, and capital gains earned from UK-based investments.
However, while the tax treaty covers where investments are taxed and when withholding taxes can be reduced, it doesn’t override domestic tax rules. Therefore, investment income, regardless of where it arises, remains subject to Portuguese tax law, which determines its classification.
Do Expats Living in Portugal Still Need to File Tax Returns in Both Countries?
Often, yes. The tax treaty doesn’t remove reporting obligations in either the UK or Portugal, so you’d still be expected to file a UK tax return to declare British-sourced incomes, even if those earnings also need to be declared to the Portuguese tax office.
The treaty prevents double taxation, but it doesn’t eliminate the requirement to report your income.
How Do Expats Claim Tax Relief Through the UK-Portugal Tax Treaty?
Another misconception is the assumption that tax treaty benefits are automatically applied, but this isn’t always the case. Instead, expats will often need to file returns with HMRC with additional forms that prevent tax being deducted at source if the income is subject to Portuguese tax.
Likewise, expats will need to include any foreign income and related credits on their Portuguese tax returns and omissions or errors can result in unnecessary overpayment of tax or an inability to reclaim tax paid at source.
What Is the Difference Between a Tax Credit and a Tax Exemption?
Tax treaties offer two ways to prevent double taxation:
- Tax credits, where tax paid in one country is offset against a liability in the other country
- Tax exemptions, where income is only taxed in one country and is excluded from taxation in the other jurisdiction
Knowing which applies to your income is essential and ensures you won’t mistakenly believe that you are exempt from a tax you need to pay or fail to claim tax credits when these are available.
What Are the Most Frequent Mistakes Expats Make When Relying on Tax Treaties in Portugal?
We’ve mentioned a couple of typical errors or assumptions, but others include:
- Misunderstanding the Portuguese tax residency rules
- Assuming that specific tax regimes eliminate all other tax obligations
- Not declaring overseas income within Portugal
It’s strongly advisable that you seek professional advice to ensure that tax treaty rules are applied correctly and on time, and before you consider relocating or restructuring your assets to make life in Portugal more tax efficient.
Further Guidance on How Expat Tax Treaties Work in Portugal
The UK-Portugal tax treaty offers protection against double taxation, but it’s also just one aspect of wealth management expats need to consider, and other factors like your income sources, long-term plans and residency status will determine how the treaty and its rules apply to you.
For more advice about a Portuguese relocation, cross-border taxation or ensuring your affairs are as tax-efficient as possible, please contact the Chase Buchanan Private Wealth Management team in Portugal we’ll be happy to assist.
© Chase Buchanan Private Wealth Management.
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*Information correct as at May 2026
