Double Taxation Agreement

A Double Taxation Agreement (DTA) is a treaty between two countries that decides which of them gets to tax a given piece of income. Without one, you could legally owe income tax in both the country where you earned the money and the country where you live. DTAs exist to prevent that.

In Portuguese, the formal name is Acordo para Evitar a Dupla Tributacao (ADT). You may also see the longer form Convencao para Evitar a Dupla Tributacao, or simply "Convencao Fiscal."

Why they exist

When a freelancer based in Portugal earns income from a client in Germany, both Portugal (as the country of residence) and Germany (as the country of the paying client) could claim the right to tax that income. For professional services invoiced to a foreign business, the answer is usually clean: Portugal taxes it, and the paying country has no claim. But for other income types, such as dividends, interest, royalties, pensions, and property income, both countries may have a legitimate claim under their own domestic laws.

DTAs set out the rules in advance so neither country is surprised and neither can take more than its treaty-allocated share.

Portugal's treaty network

Portugal has concluded DTAs with more than 80 countries. The network covers most of Europe, the United States, Canada, Brazil, and large parts of Asia and Africa. When Portugal has a DTA with the country your income comes from, the treaty governs. When no treaty exists, Portuguese domestic law applies unilaterally.

Most treaties follow the OECD Model Tax Convention as a drafting template. Individual treaties deviate from the model in specific areas, so the actual treaty text always takes precedence over any general description of how DTAs work.

One notable change in recent years: the Portugal-Sweden DTA was terminated in 2022 and is no longer in force.

How relief is given in Portugal

Portugal typically uses one of two mechanisms when a DTA applies.

The exemption method means Portugal agrees not to tax certain foreign-source income. The income is exempt from Portuguese IRS. It may still be used to calculate the rate that applies to your other income (the "progression clause"), but no Portuguese tax is actually charged on it.

The credit method is governed by article 81 CIRS (Codigo do Imposto sobre o Rendimento das Pessoas Singulares). Portugal taxes the foreign income but gives you a credit for the tax already paid in the source country. The credit reduces your Portuguese IRS liability, so you end up paying no more than the higher of the two countries' rates on that income. For most expat freelancers with foreign income, this is the mechanism that shows up at filing time.

Which method applies depends on the income type and the specific treaty. Professional service income from foreign clients typically falls under article 7 (business profits) of the OECD model, and Portugal usually has the exclusive right to tax it. Dividends and interest often involve a shared taxing right with a capped withholding rate in the source country. Pensions are typically exclusive to the residence country.

What this means for Categoria B freelancers

If you are a trabalhador independente in Portugal invoicing clients abroad, the DTA question is usually straightforward: Portugal taxes your professional service income, and the client's country does not withhold anything. The income is declared in Anexo B of Modelo 3 as Categoria B income, the same way any Portuguese-source service income is declared.

Foreign income that falls outside article 7 (business profits) is handled differently. Dividends from a foreign company go in Anexo E. Rental income from foreign property goes in Anexo F. Employment income earned abroad goes in Anexo A. Income from all foreign sources that falls outside the domestic categories goes in Anexo J. Each annex has its own section for indicating DTA relief, and the AT system applies the credit or exemption during the calculation step.

For income that is exempt under a DTA but still counted for rate progression purposes, the amount still appears in the declaration even though no tax is charged on it.

The interaction with NHR and IFICI

Holders of the NHR regime or its successor IFICI (Incentivo Fiscal a Investigacao Cientifica e Inovacao) start from a different position. Under old NHR, many categories of foreign-source income were already exempt in Portugal under domestic Portuguese law regardless of whether a DTA existed. Under IFICI, foreign-source Categoria A and Categoria B income, dividends, interest, rental income, and capital gains are exempt (subject to exceptions for income from blacklisted jurisdictions).

When both a DTA and an NHR or IFICI exemption exist for the same income, the domestic exemption usually handles the relief and the treaty provides additional legal certainty about the source country's rights. The practical result for most NHR and IFICI holders is that qualifying foreign income bears no Portuguese tax, and the DTA reinforces that outcome at the treaty level.

Finding the treaty text

The AT publishes the full list of DTAs in force on Portal das Financas (Portaria). Each treaty is available as a PDF in both Portuguese and the treaty partner's official language.

For individual taxpayers, the articles that matter most are typically: article 7 (business profits), article 15 (employment income), article 10 (dividends), article 11 (interest), article 12 (royalties), and article 18 (pensions).

For the step-by-step process of declaring foreign income in Modelo 3, including Anexo J and how to enter DTA relief, see how to file your IRS return in Portugal.