Written with people moving from Turkey in mind. The Portuguese rules still apply more broadly.
Entry Requirement: Return Ticket
If you enter Portugal on a tourist visa (or visa-free) intending to apply for residency later, border control may still demand proof of a return flight. Failing to show this can lead to denied entry.
Even if you have a D-type visa, carrying a one-way ticket is safer only if your visa explicitly allows for residency. For tourists scouting the country, a refundable return ticket is the best safety net.