What do I have to file in Portugal as a US citizen?
If you are resident there, a Portuguese return, prepared on the terms of whatever status you registered under. Alongside it the return in the other country continues, because that obligation carries on regardless of the Portuguese treatment of the same income. A special status changes how income is treated inside the Portuguese return; it does not remove the return, and it does not remove the other one. The first piece of work on this corridor is therefore the registration record, because it determines how one of the two returns has to be prepared.
Do I still file a US return if Portugal exempts my income?
Yes. An exemption on one side says nothing about the filing obligation on the other, and on this corridor the US obligation continues regardless of what Portugal does with the income. An exemption usually makes the other return matter more, because relief there is given for tax actually paid and there is now none to claim. So the return is filed, the income is reported, and the charge is whatever the residual rules produce. Treating a Portuguese exemption as the end of the matter is the most common error here.
Does my special status change the Portuguese return I file?
It changes what goes into the return and how items are treated, not whether one is due. Which version of the terms applies to you depends on your own registration rather than on the regime as currently described, so the same income can be entered differently by two people filing in the same year. That is why the registration is read before the return is drafted. Keep the record with the tax papers, because the same question arises every year and the answer is fixed by the terms you entered under.
What US reporting do I have while living in Portugal?
Alongside the return there is separate reporting about accounts and assets held outside the country, triggered by holding them rather than by income arising on them. Moving to Portugal typically creates several at once, such as a local bank account and perhaps a local plan or property, so the year of the move is when the reporting inventory grows. Build the list from everything you can sign on rather than from whatever produced income, and revisit it each year. This is the part clients most often have to bring up to date afterwards.
Do I file in both countries the year I move to Portugal?
Yes. Portugal assesses the part of the year its residence rules reach, so its return covers a period, while the other country return covers the whole of it. If you registered under a special status partway through, that adds a date of its own inside the same year. The filings are separate documents on separate timetables, and the items that straddle the move are allocated once and then reported the same way in both. Doing the allocation before either return is drafted saves preparing both of them twice.
What do I file in Portugal on rent from a US property?
The letting comes into your Portuguese return as a resident, and the country the property sits in has its own claim on it, so the same rent is reported twice on two measures of profit. Expenses, depreciation and the treatment of improvements do not match between the two systems, which means one set of records has to be recast rather than copied across. How your registered status treats foreign property income decides the Portuguese figure, so that is checked before the return is prepared.
What is a permanent establishment, and how easily do we create one?
A taxable presence in another country under the treaty — typically a fixed place of business such as an office, branch, factory or workshop, or a dependent agent habitually concluding contracts on your behalf. Some treaties add a services test measured in days. Purely preparatory or auxiliary activity is excluded, but that carve-out is narrower than it sounds: one senior employee working from home in the other country, with authority, has been enough. See business profits and permanent establishment.
Is double taxation legal?
Yes. Nothing prevents two countries from taxing the same income under their own domestic law — each is exercising its own jurisdiction. What treaties and credit systems do is relieve the outcome rather than prohibit the charge, and relief is generally something you must claim on a return or a form, not something applied automatically. Miss the claim and the double charge stands. Double taxation explains the mechanism.
