If I move to Portugal in September, do I pay tax on the whole year?

This is one of the few places where the Portuguese rules are kinder than people expect, and it makes the timing of a move genuinely worth planning.

How the split works

Residency runs from the first day of stay to the last day of stay rather than for a whole calendar year. Move on 15 September 2026 and you are a Portuguese tax resident for 15 September to 31 December 2026. Your worldwide income from that date is in scope. The salary, bonus or client invoices you earned in the eight months before, while you were resident somewhere else, are not swept in by the move.

What that lets you plan

1. A bonus, a share vesting or an exit payment landing before your arrival date sits outside the Portuguese base.
2. A property or securities sale is treated the same way, which is why the completion date and the arrival date should not be chosen independently.
3. Nothing here overrides the other country's rules, and both sides have to agree on your dates, so a treaty tie breaker can still move the line.

The traps in the same year

Your NIF address is the signal the tax authority reads, so switching it to a Portuguese address months before you actually move can undo the split you were counting on. The habitual residence test has the same effect: a lease signed and occupied in June with the family in it is hard to reconcile with a September start date.

The IFICI calendar, in the same breath

An autumn arrival makes you resident for that year, and the deadline to register for IFICI is 15 January of the following year. September to January is not much runway for a file that a separate body has to assess.

You still file a Modelo 3 for that first part year, between 1 April and 30 June of the following year. See when do I become a tax resident and model the part year in the tax estimator, which assumes a full year unless you scale the figures yourself.