The Supreme Administrative Court judgment, case no. 162/25.4BALSB, of 25 February 2026, has harmonized the case law on the question of whether income earned abroad by companies’ resident in Portugal should, or should not, be taken into account for the purposes of determining the municipal surtax. In that ruling, the Supreme Administrative Court held that income earned abroad will only be excluded from municipal surtax where it can be effectively imputable to a branch or permanent establishment located therein, since only in that case may the income be regarded as having been effectively generated outside the geographical boundaries of the municipality.

This decision departs from part of several arbitral case laws previously issued, in particular the CAAD decision of 29 July 2025, case no. 73/2025-T, which had held that income generated outside the national territory, including interest paid by foreign entities, should be excluded from the municipal surtax taxable base.

According to the Supreme Administrative Court, the concept of “generated income”, for the purposes of article 18 of the Local Authorities’ Financial Regime, requires more than the mere foreign source of the income. It is therefore not sufficient to show that the income arises from a foreign source. It is necessary to demonstrate that such income was effectively generated through a structure located abroad, namely a branch or permanent establishment, with sufficient autonomy to justify its disconnection from the Portuguese municipality in which the company has its registered office or place of effective management.

Accordingly, taxable persons that are unable to demonstrate the existence of a branch or permanent establishment abroad to which the generation of the income may be attributed now face an increased risk of such income being subject to municipal surtax in the municipality of their registered office or place of effective management. In practice, this line of case law significantly restricts the possibility of excluding foreign-source income from the municipal surtax taxable base, limiting such exclusion to situations where there is a sufficiently strong material and organizational connection with a foreign structure.

This harmonization of case law is of particular relevance for corporate groups and resident companies carrying on international operations, making it advisable to review their operational, documentary and tax structure, particularly where the intention is to support the non-application of municipal surtax to income derived from abroad.

For further information on this matter, please do not hesitate to contact the Tax Department of Ana Bruno & Associados, Sociedade de Advogados, SP, Lda.