Prep your IRS Modelo 3 in 9 questions

It depends on where your income came from, and that's what the questions above work out. The common ones: Anexo A for Portuguese salary and pensions (art. 2.º CIRS), Anexo B for freelance income under the simplified regime (arts. 3.º + 28.º), Anexo F for rent (art. 8.º), Anexo G for capital gains (art. 10.º), Anexo H for deductions (art. 78.º), and Anexo J for anything earned outside Portugal (arts. 15.º + 81.º).

1 April to 30 June, every year. Unusually, this deadline does not roll forward when 30 June falls on a weekend or a holiday — art. 60.º n.º 1 says so explicitly, so treat 30 June as final regardless of the day it lands on.

By 31 August, if you filed on time. The 31 July date you'll see quoted in a lot of places is the AT's deadline to issue your assessment, not your deadline to pay — they're different things and only one of them is your responsibility.

No. The pre-fill is built from what Portuguese third parties reported — employers, banks, e-Fatura. Foreign income and any foreign tax you paid on it are yours to enter, on Anexo J. Assuming the pre-fill is complete is one of the easiest ways to under-declare without meaning to.

A late income declaration carries an RGIT fine of €150 to €3,750, reducible if you come forward voluntarily, plus compensatory interest accruing day by day. You also forfeit the interest the state would otherwise have paid on a refund. Filing late beats not filing — the penalty grows with the delay.