Remote Work in Portugal for a Foreign Employer: Tax, Social Security

If you live in Portugal and work remotely for an employer abroad, Portugal taxes you as a resident on that salary, and the tax authority asks you to declare it with the foreign tax already paid so that you are not taxed twice. Social security is a separate question: the U.S. and U.K. agreements both start from the country where you work, with a certificate of coverage as the exception for people sent abroad temporarily by their employer.

This is the work-and-tax companion to working in Portugal as an American or a Briton and to the remote work visa guide. It reports what the official pages say, read on 18 October 2026. It is not tax or legal advice. The latest change it relies on is the entry into force, on 29 December 2025, of the new U.K.-Portugal double taxation convention, which is why the update date is the date of that change. Where a page does not say something, we say so rather than fill the gap.

When does Portugal tax your foreign salary?

Portugal taxes you on worldwide income if you are a tax resident. Article 16 of the personal income tax code (CIRS) says people are resident in Portuguese territory if, in the year the income relates to, they:

• stayed there more than 183 days, consecutive or not, in any 12-month period beginning or ending in that year; or
• stayed less time but, on any day of that period, had a home in conditions that suggest an intention to keep and occupy it as their habitual residence.

The tax authority’s page on income obtained abroad then says residents must declare in Portugal all income obtained in Portugal and abroad. Its FAQ gives the same rule and says the tax applies to income wherever it is obtained, including salaries of employees (category A) and business and professional income (category B). The consolidated text of article 16 we read is the version up to December 2023, and it shows paragraphs 8 to 12 of that article marked as repealed by Law 82/2023 of 29 December. How and when you become a resident is a separate subject, and we plan a guide on it.

One practical warning from the FAQ: if you move abroad and do not update your tax address, the tax authority keeps treating you as resident and the double taxation can only be corrected afterwards. The mirror image is just as true for a newcomer: the address you register matters.

How do you declare it?

You file the Modelo 3 income tax return and add Annex J for income from abroad. The tax authority says the filing period runs from 1 April to 30 June of the year after the income. The Annex has a table for employment income from abroad (table 4) and one for business and professional income (table 6). In each table the tax authority asks for:

The foreign tax is counted as a credit for international double taxation when the final Portuguese tax is worked out. Article 81 of the CIRS sets the limit: the credit is the lower of the income tax paid abroad and the part of the Portuguese tax, calculated before the deduction, that corresponds to the income that may be taxed in that country. Where a tax treaty exists, the deduction cannot exceed the foreign tax paid as provided by the treaty. If the credit cannot be used because the Portuguese tax is too low that year, the same article carries the remainder over to the five following tax years.

Article 81 also contains a different method for taxpayers under article 58-A of the Tax Benefits Statute: it applies an exemption method to some foreign income, which is still counted to set the rate on the rest. That is a special regime for some new residents, which we did not read beyond this article and cover separately.

You need a NIF before any of this. The government’s guide for migrants adds that anyone who wants to work in Portugal, as an employee or independently, must have a social security number (NISS).

Do the tax treaties change who taxes you?

Both treaties have an employment article with the same core wording. We read the U.S. convention (in force since 1 January 1996) and the U.K. convention signed on 15 September 2025.

Americans. Article 16(1) of the U.S.-Portugal convention says salaries derived by a resident of one State “shall be taxable only in that State unless the employment is exercised in the other”. Paragraph 2 keeps the tax in the first State for a visitor whose presence does not exceed 183 days in the aggregate, paid by an employer who is not a resident of the other State and does not bear the pay through a permanent establishment there. Read with those words, a person who is resident in Portugal and does the work in Portugal falls under Portugal’s right to tax. That is our reading of the text, not a sentence the pages state about remote work.

The convention does not end U.S. tax for a citizen. Its protocol says the United States may tax its citizens as if the convention had not come into effect. Article 25 then provides relief: the United States gives a credit for Portuguese income tax, and for a U.S. citizen resident in Portugal, income taxable by the United States solely because of citizenship is treated as arising in Portugal to the extent needed to avoid double taxation. How the foreign earned income exclusion and the foreign tax credit work in practice is in our guide to U.S. taxes from Portugal.

Britons. The new U.K.-Portugal convention was signed in London on 15 September 2025 and, per HMRC, entered into force on 29 December 2025. HMRC gives these dates of effect: in the U.K. from 1 January 2026 for taxes withheld at source and from 6 April 2026 for Income Tax and Capital Gains Tax; in Portugal from 1 January 2026. HMRC lists the 1968 convention as not in force. Article 14 of the new convention carries the same employment wording as the U.S. article, including the 183-day test, and article 21 provides relief: Portugal deducts the U.K. tax paid, within a cap, and the U.K. allows a credit for Portuguese tax within U.K. law.

Separately, HMRC’s page on U.K. income for people abroad says you usually have to pay tax on U.K. income even if you are not U.K. resident, wages included, and that if you live abroad and are employed in the U.K., your tax is calculated automatically on the days you work in the U.K. It does not say how this applies to days worked from Portugal for a U.K. employer, so take that question to HMRC or an adviser. U.K. residence itself is a different test that we did not read.

Which country’s social security applies?

This is where the two nationalities differ most. In both cases the pages read set a general rule by place of work, and an exception for workers sent abroad temporarily by their employer.

What this means for someone who moved to Portugal and kept their job, on our reading of those pages: the detached worker exceptions are written for employees an employer sends abroad, and the SSA says self-employed residents of Portugal are assigned Portuguese coverage. The pages do not mention remote work or a worker who relocates on their own, so we cannot tell you from them that a given remote worker stays under U.S. or U.K. coverage. If your employer says it will keep paying U.S. Social Security or U.K. National Insurance for you, ask for the certificate of coverage: both countries say it is the proof. HMRC adds that the certificate is not a work permit.

Two points specific to each side:

• Americans. The IRS says a person claiming exemption from U.S. Social Security and Medicare taxes because of a totalization agreement must obtain a certificate of coverage from the social security agency of their home country and give it to the U.S. employer. A self-employed person attaches a copy to the U.S. return each year, per the SSA. The SSA’s Portugal page says the U.S. agreement dates from 1 August 1989.
• Britons. The EU rules apply differently to people in the scope of the Withdrawal Agreement, for example U.K. nationals who were resident or started working in an EU country before 1 January 2021, and our Brexit guide for Britons covers that group. HMRC says you might be able to pay voluntary National Insurance contributions, and that you may want to think about paying them, to protect benefits and State Pension; it says that they do not cover health insurance where you live, and that you may contribute voluntarily to only one system at a time. For health cover in Portugal, see the healthcare guide.

What do the pages not settle?

Four things we could not establish from official pages, and that you should check before you rely on this article:

• How Segurança Social treats a worker in Portugal whose employer has no Portuguese company, and who registers or pays. The Segurança Social pages on the United States, on the United Kingdom and on workers employed by a foreign employer showed no content in either of the browsers we tried, so we state nothing from them.
• Whether Portugal is listed in the EU-U.K. annex for the 24-month detached worker rule. HMRC’s update note of 12 February 2021 says all member states have expressed their wish to opt in, but the list in Annex SSC-8 did not appear in the text of the agreement we read on EUR-Lex.
• How your employer’s payroll abroad should treat you. HMRC’s employer guidance says employers must keep calculating PAYE and National Insurance in certain cases and “check with the social security institution” of the destination country in others, but it does not cover remote work from Portugal.
• Your U.K. or U.S. residence status for tax, which has its own tests.

What should you do, step by step?

1. Check your visa route. The remote work visa and residence permit decide your right to work from Portugal, see the remote work visa guide.
2. Get your NIF and NISS, and register your Portuguese address with the tax authority when you become resident.
3. Ask your employer which country’s social security it will pay for you, and whether it holds or will request a certificate of coverage.
4. Keep your foreign payslips and records of the foreign tax and social security paid, the three amounts that Annex J asks for.
5. File the Modelo 3 with Annex J between 1 April and 30 June of the following year; Americans also file in the U.S., see the U.S. taxes guide.
6. If the situation is not routine, for example a self-employed contractor or a company with no Portuguese presence, take it to Segurança Social, the tax authority and an adviser before you sign. See also freelancing and the independent worker regime, working as an employee and the IFICI regime for new residents.

More guides on this site: Portuguese tax residence; UK taxes and HMRC for Britons in Portugal; what the U.S.-Portugal tax treaty says; the foreign earned income exclusion and foreign tax credit; the U.S. agreement (the page says nothing on remote work).

Date of the information

Official pages read for this guide, all on 18 October 2026: the Portal das Finanças page and FAQ on income obtained abroad and the CIRS articles 16 and 81 (consolidated to December 2023, Law 82/2023 of 29 December 2023); the text of the U.S.-Portugal income tax convention on IRS.gov; HMRC’s treaty page for Portugal (last updated 8 January 2026) and the text of the 2025 U.K.-Portugal convention; HMRC’s pages on U.K. income for people abroad and on National Insurance for work abroad and in the EU (the EU page was last updated 17 January 2024); the SSA’s pages on U.S. agreements and on the agreement with Portugal; the IRS page on totalization agreements (reviewed 14 March 2026); the Protocol on Social Security Coordination of the EU-U.K. Trade and Cooperation Agreement in the Official Journal of 30 April 2021; and the government’s guide for migrants (updated 5 May 2026). Several pages carry no date of their own.