NIF

Número de Identificação Fiscal — your Portuguese tax number, needed for practically everything: bank account, rental contract, purchase, utilities, even a phone plan. Non-residents usually obtain it through a fiscal representative, ideally before moving.

Where people slip: the NIF carries an address — your morada fiscal. If it still points abroad through a representative after you move, Finanças keeps treating you as non-resident, letters go to the wrong place, and some online services simply refuse you. Updating the address is a separate step that nobody reminds you about.

Do this: get the NIF before you arrive, then change the morada fiscal the moment you have a Portuguese address — and end the representation once you are resident, otherwise you keep paying for it.