As a rule of thumb, if you spend less than half of the year in Portugal, you are considered a non-tax resident, and are in consequence only taxed on income obtained in Portugal. If you become a tax resident in Portugal, there is the option to become a non-habitual resident of Portugal and be exempt from paying taxes on worldwide income in Portugal. However, Portuguese-sourced income would be taxed at a flat rate of 20% during the first 10 years, with the ability to pass your wealth to a spouse or dependent without any incurring inheritance taxes.