How is capital gains taxed in Portugal? As this is real estate income, capital gains on real estate in Portugal are always taxed in the country where the property is located, in application of the 1971 tax treaty between France and Portugal to avoid double taxation. Capital gains are taxed in Portugal. Capital gains tax in Portugal is payable at the same time as income tax. So you'll need to declare it on your Portuguese income tax return. All property sales must be declared to the ’Autoridad...