If you have moved to Portugal from the UK, sooner or later a deceptively simple-looking form called the Modelo 3 lands on your to-do list – and it catches more expats out than almost anything else I deal with.

The Portuguese tax return is not the monster people fear, but it works very differently from the UK system, and getting it wrong can mean paying tax twice or facing penalties you never saw coming. This guide walks you through who needs to file, what the Modelo 3 actually is, the 2026 deadlines, and exactly how to declare your UK pensions, savings and other income without tripping over the double taxation rules.

Do You Even Need to File a Portuguese Tax Return?

The first question is whether you are tax resident in Portugal at all. In broad terms, you become Portuguese tax resident if you spend more than 183 days in the country in a 12-month period, or if you have a home here that you clearly intend to keep as your habitual residence. Once that happens, Portugal taxes you on your worldwide income – not just money you earn locally.

That last point is the one that surprises people most. Your UK state pension, your private pension drawdown, rental income from a flat in Manchester, dividends from an ISA – in Portuguese eyes, all of it is potentially in scope once you are resident here. The fact that it is paid in sterling into a UK bank account makes no difference.

In my experience working with clients across the Algarve, the people who get into trouble are usually those who assumed that because their income stays in the UK and is sometimes already taxed there, Portugal has nothing to do with it. That assumption can be expensive. Even if you owe little or nothing here thanks to a tax treaty, you may still be legally required to declare the income.

Meet the Modelo 3 – Portugal’s Annual Tax Return

The Modelo 3 is the main personal income tax return, equivalent in spirit to the UK’s Self Assessment. It is submitted online through the Portal das Finanças, the tax authority’s website, using your taxpayer number (NIF) and password.

What makes it feel unfamiliar to Brits is that the form is built from a core return plus a series of anexos (annexes), and you only complete the ones relevant to you. The annexes that matter most to UK expats are usually:

• Anexo J – for declaring foreign income of all kinds: overseas pensions, interest, dividends, rental income and capital gains earned outside Portugal. For most UK expats, this is the big one.
• Anexo H – for tax deductions and benefits, such as health and education expenses incurred in Portugal.
• Anexo L – relevant if you hold the Non-Habitual Residence (NHR) status, used to claim the special treatment that regime allows.

The system pre-fills some Portuguese-source data automatically, but it will almost never know about your UK income. That part is on you to report accurately, which is why the foreign-income annex is where most of the care needs to go.

The 2026 Filing Deadlines You Cannot Miss

Portugal runs on the calendar year, so the return you file in 2026 covers income received during 2025. The filing window opens on 1 April and closes on 30 June – which means as you read this, the window is open right now.

Unlike the UK, where the deadline depends on whether you file on paper or online, Portugal gives everyone the same window regardless of income type. There is no separate later date for the self-employed or for those with foreign income. Miss 30 June and you are into late-filing territory, with fines that start modestly but climb if you keep ignoring them.

Once you submit, the tax authority issues an assessment (the nota de liquidacao) over the following weeks, telling you whether you owe more or are due a refund. If there is tax to pay, it is generally due by the end of August. My advice to clients is always the same: do not leave it to the last week of June. Gathering UK income figures – especially pension and investment statements that run on a UK tax year ending 5 April – takes longer than people expect.

Declaring Your UK Income: Pensions, Interest and Dividends

This is the heart of the matter for most UK expats, and it is where the detail really counts. Different types of income are treated differently under the UK-Portugal Double Taxation Agreement, so it is worth understanding the broad categories before you start filling in boxes.

Private and workplace pensions: Once you are Portuguese tax resident, most UK private and occupational pensions are taxable in Portugal, not the UK. To stop HMRC also taxing them at source, you apply for an NT (No Tax) code so the pension is paid gross, then declare it here. Getting that sequence right avoids the classic double-tax headache.

Government service pensions: Pensions for former civil servants, military, police, teachers in state schools and similar roles are a notable exception – under the treaty these usually remain taxable only in the UK. You may still need to report them in Portugal for rate-setting purposes, but you should not be taxed on them twice.

UK savings interest and dividends: Interest from UK banks and dividends from shares are generally taxable in Portugal once you are resident. Crucially, the UK tax-free wrapper of an ISA means nothing here – Portugal does not recognise ISAs, so the income and gains inside them are fully reportable. This catches out a huge number of people who assumed their ISA was untouchable.

Rental income from UK property: Income from a UK property is taxable in the UK first (the UK keeps taxing rights on its own land), but it must also be declared in Portugal, with relief given for the UK tax already paid so you are not charged twice on the same money.

How Double Taxation Relief Actually Works

The fear of paying tax twice is what keeps people up at night, but the UK-Portugal treaty exists precisely to prevent that. The principle is that each type of income has a country with primary taxing rights, and the other country either steps back or gives you credit for tax already paid.

In practice, when you complete Anexo J you declare the gross foreign income and, where relevant, the foreign tax paid. Portugal then applies its rules to either exempt the income or grant a credit. The result is that you should never pay more than the higher of the two countries’ tax on a given slice of income – but you only get that protection if you declare everything correctly and keep the paperwork.

This is also why the order of operations matters so much with pensions. If you start drawing a UK pension before sorting your NT code and Portuguese residency paperwork, you can end up with tax deducted in the UK that you then have to chase back through a refund claim – a slow and irritating process. A little planning up front saves months of admin later.

Common Mistakes UK Expats Make on the Modelo 3

After years of untangling these returns, the same handful of errors come up again and again. Knowing them in advance is half the battle.

• Assuming UK-taxed income does not need declaring. Even income that is correctly taxed in the UK often still has to be reported in Portugal. Reporting is separate from paying.
• Forgetting ISAs and other tax wrappers. Portugal sees straight through them. The income inside is reportable like any other.
• Missing the NT code step. Drawing a pension without arranging gross payment leads to double taxation and a refund chase.
• Using the wrong exchange rate or period. UK figures run to 5 April; Portugal wants the calendar year. You generally convert to euros using accepted reference rates, not whatever the rate happened to be on the day.
• Overlooking the foreign bank account declaration. Portuguese residents must report holding accounts outside Portugal – a separate box that is easy to skip.

Frequently Asked Questions

Do I have to file a Portuguese tax return if all my income is from the UK?

Almost certainly yes, if you are tax resident in Portugal. Residency, not the source or location of your income, is what triggers the filing obligation. You declare worldwide income on the Modelo 3 even if much of it has already been taxed in the UK, and the treaty then prevents you being taxed twice.

When is the 2026 Portuguese tax return deadline?

The window for declaring 2025 income runs from 1 April to 30 June 2026. Everyone files within the same window regardless of income type, and any tax owed is generally payable by the end of August.

Is my UK ISA tax-free in Portugal?

No. Portugal does not recognise the ISA wrapper, so the interest, dividends and gains within it are taxable and reportable like any other investment income once you are Portuguese resident. This is one of the most common and costly misunderstandings.

Will I be taxed twice on my UK pension?

You should not be, provided you handle the paperwork correctly. For most private pensions you apply for an NT code so the UK pays you gross, then declare and pay tax in Portugal. Government service pensions are an exception and usually stay taxable in the UK only.

Can I file the Modelo 3 myself?

Many people do, through the Portal das Finanças. But if you have UK pensions, investments or property, the foreign-income sections reward getting professional help at least the first time, so the framework is set up correctly and you are not overpaying.

What to Do Next

The Portuguese tax return is manageable once you understand that residency makes your worldwide income reportable, that the Modelo 3 deadline is 30 June, and that the double taxation treaty is there to protect you – but only if you declare everything properly. Get the pension paperwork in the right order and the rest tends to follow.

If you would like to discuss how this affects 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 in making sure the tax side is handled correctly from day one. You may also find our guides on drawing UK pensions while living in Portugal useful as a companion to this one.

Please note this article is general information, not personal tax advice – your own position should always be checked against your circumstances and current rules, which you can verify via the Portuguese tax authority at Portal das Financas and HMRC guidance on foreign income.

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

Contact us