In a recent court case between an American citizen and the Portuguese tax authorities, ruling was in favour of the American citizen who reclaimed a sizeable amount of tax that had been paid in Portugal.
The double taxation agreement (DTA) between Portugal and the USA stipulates in the “protocol” that the USA reserves the right to tax its citizens as if the DTA was not in force/operation. Under the NHR rules, if the foreign jurisdiction has the right/option to tax you then it is tax free in Portugal, irrespective of whether the foreign jurisdiction actually levies a tax on this income or not.
The outcome of the case indicates serious benefits for American citizens paying tax in Portugal under the NHR regime with foreign capital gains.