Before you start

A NIF (Portuguese tax number)
Clarity on your residency status (the 183-day rule or a habitual residence in Portugal)
Access to the Portal das Financas (the tax authority's online portal), usually via a password or Chave Movel Digital
Records of worldwide income and any foreign tax paid (for double-taxation relief)

Step-by-step

1
Work out if you are tax-resident
You are generally Portuguese tax-resident if you are in Portugal more than 183 days (continuous or not) in any 12-month period, or you have a home here that suggests habitual residence. Residents are taxed on worldwide income; non-residents only on Portuguese-source income. This status drives everything that follows.
OnlineWho: You (verify with an accountant if unsure)Assess on arrival-
2
Register your status and tax address with Financas
Update your details on the Portal das Financas: set your tax residence and address. If you think you qualify for the new IFICI incentive (NHR 2.0), there is a separate application with a deadline early in the year after you become resident, and it requires meeting the eligibility criteria for an approved profession or activity.
OnlineWho: You (Portal das Financas / accountant)After you become resident; IFICI has an annual application deadlineFree to register
3
Understand the rate that applies to you
Standard IRS is progressive across brackets up to around 48%, with an extra solidarity surcharge on income above high thresholds. If you secured old NHR before it closed, you keep its benefits for the remainder of your 10-year period. If you qualify for IFICI, eligible employment/self-employment income can be taxed at a flat 20%; otherwise the normal progressive scale applies.
OnlineWho: You (with an accountant for anything non-trivial)Ongoing-
4
File your annual IRS return
Residents file an annual IRS return (Modelo 3) on the Portal das Financas, generally between April and June for the prior calendar year. Portugal has many double-taxation treaties, so foreign tax paid can often be credited - keep records. An accountant is strongly recommended in your first year and for any cross-border income.
OnlineWho: You (or a certified accountant / contabilista)Filing window typically April-June each yearSelf-filing is free; an accountant commonly charges from ~EUR 100+

Documents you’ll need

NIF (Portuguese tax number)
Portal das Financas access (password or Chave Movel Digital)
Records of worldwide income (employment, self-employment, rental, investment)
Proof of any foreign tax paid (for double-taxation relief)
For IFICI: evidence of an eligible profession/activity and that you were not Portuguese-resident in the prior years required

Things most newcomers don’t know

The old NHR regime is closed - do not count on the famous 20% deal.

The Non-Habitual Resident regime that drew so many expats with a flat 20% rate and foreign-income exemptions stopped accepting new applicants from 2024. If you arrive now expecting classic NHR, you will not get it - this is the single biggest change to know.

Source: PwC Tax Summaries / portaldasfinancas.gov.pt

IFICI (NHR 2.0) replaced it, but it is much narrower.

The successor incentive - IFICI, the tax incentive for scientific research and innovation, dubbed NHR 2.0 - can still give a flat 20% on eligible income, but it targets specific qualified roles in science, tech, and innovation rather than being broadly available, so far fewer people qualify.

Source: PwC Tax Summaries / official

Residency is the 183-day (or habitual-home) test, and it means worldwide income.

Spend more than 183 days in Portugal in any 12 months, or keep a home here, and you are tax-resident on your worldwide income - not just Portuguese earnings - which is why getting your status and treaty relief right matters.

Source: PwC Tax Summaries / official

Get an accountant for your first return and any cross-border income.

Between progressive brackets, the solidarity surcharge, treaty relief, and the NHR-to-IFICI transition, the rules are genuinely nuanced. A contabilista in year one is cheap insurance against costly filing mistakes.

Source: expat / provider consensus

Common mistakes to avoid

Moving to Portugal assuming the old NHR 20% regime is still open to new applicants - it is not
Assuming you automatically qualify for IFICI - eligibility is limited to specific qualified activities
Forgetting that as a resident you are taxed on worldwide income, not just Portuguese-source income
Missing the spring IRS filing window or the separate early-year IFICI application deadline