The Portuguese tax system is constituted by a set of state and local taxes levied on income, in addition to other taxes imposed on certain particular deeds or situations. The income taxation is operated by two taxes: Personal Income Tax (IRS) and the Corporate Income Tax (IRC).
If a third country national establishes residence in Portugal, the earned income can be subject to taxation, even if from another country. Double taxation occurs when income arising in one country is received by someone residing in another country, and the subject is taxed in both countries. To avoid or reduce double taxation, Portugal has signed Conventions with some countries, namely all EU member states.
A researcher coming from another State will have to obtain a tax identification number (NIF), essential to relate to the Taxation Administration, personally or through any singular or collective person in any tax office or "Loja do Cidadão". This tax card can be obtained upon the presentation of a valid passport at the local tax office.
Every year the researcher or student will have to hand in an annual income statement ("modelo 3") and respective annexes in the second quarter of the year that follows the one when the income was earned. The amounts received are declared in this form, under the same circumstances as Portuguese nationals.
Valued Added Tax (VAT) applies to transmission of goods, provision of services and import of goods. Rates vary from 6% to 23% in mainland Portugal.
If you live in Portugal and have income from another country, you don't have to be taxed twice. You can find the information you need about the countries with a convention to avoid "double taxation" in Portugal on the Finance Portal.
For further information, please contact the Ministry of Finance Site or General directorate of contributions and taxes.