Dependents and Household on Your Portuguese IRS

• A dependant is generally a child under 18, or under 25 if studying and earning less than the minimum wage — disabled dependants qualify regardless of age.
• Married couples and unidos de facto choose separate or joint taxation each year; joint filing splits combined income by two (quociente familiar) before applying tax rates.
• Each dependant is worth a fixed €600 deduction (more for children under 3 or a second-and-later child under 6), on top of shared-custody and disability variants.
• You must confirm your household composition with the Autoridade Tributária by 15 February — it locks in who's a dependant on that year's return, not just a filing preference.

Portuguese IRS treats your household — agregado familiar — as a unit, even though income is generally taxed on an individual basis. Getting the composition right matters well beyond the return itself: it determines who can claim a child's health and education expenses, whether you file jointly or separately, and how much each dependant is worth in deductions.

Who counts as a dependant

Article 13 of the Código do IRS defines dependants precisely. To count, they must be identified by tax number (NIF) on the return. The categories are:

• Children, adopted children, and stepchildren who are minors and not emancipated, plus minors under legal guardianship (tutela).
• Children, adopted children, and stepchildren who are adults — plus anyone who was under guardianship until adulthood — provided they're not over 25 and don't earn more annually than the guaranteed minimum monthly wage.
• Children, adopted children, stepchildren, and wards of any age who are unfit for work and unable to support themselves — no age limit applies here.
• Civil godchildren (afilhados civis) who were under guardianship until adulthood, under the same age-25 and income conditions as above.

Your household composition is judged as it stood on 31 December of the tax year — not on the day you file. A dependant can't belong to more than one household at once, except where parental responsibilities are shared between two taxpayers who aren't part of the same household: in that case, each parent can include the child on their own return for income-attribution and deduction purposes, split according to their custody agreement.

Joint vs. separate filing (tributação conjunta vs. separada)

If you're married and not judicially separated, or in a unido de facto relationship, you and your partner choose each year between separate and joint taxation — the choice isn't permanent and must be exercised again on every return.

• Separate taxation (the default): each partner files their own return, declaring their own income plus 50% of any dependants' income that belongs to the shared household.
• Joint taxation (opt-in): one return covers the combined income of everyone in the household. Both partners must actively elect it on the declaration, and the choice only holds for that year.

Joint filing doesn't just add the numbers together — Article 69 applies a quociente familiar: combined taxable income is divided by two, tax rates are applied to that half, and the result is doubled to get the final tax due. For most couples this softens the effect of progressive brackets compared to summing incomes outright, though whether it beats separate filing depends on how unevenly the two incomes are split.

How the per-dependant deduction works

Article 78-A sets a fixed deduction per dependant, applied directly against the tax due (not against taxable income):

• €600 per dependant, as a baseline.
• €300 per dependant instead, split between both parents, when a shared-custody agreement sets joint parental responsibility with alternating residence for the child.
• An extra €126 (or €63 under the shared-custody split) when the dependant is 3 or under by 31 December of the tax year.
• An extra €300 (or €150 under the shared-custody split) for the second and each subsequent dependant who is 6 or under by 31 December — this doesn't stack with the under-3 bonus for the same child.
• €525 per ascendant (e.g., a parent) who genuinely shares your household and doesn't earn more than the minimum state pension, plus €110 more if that's the only qualifying ascendant.

Households with three or more dependants also get a 5% increase, per dependant beyond the second, to the combined cap on several other deductions (health, education, general household expenses, and a few others) — a meaningful boost for larger families. If the same dependant is declared on more than one return, the deduction is automatically halved for each taxpayer claiming them.

Why the mid-February deadline matters

Every year, the Autoridade Tributária's fiscal calendar sets 15 February as the date to confirm — or update — your household composition (comunicação do agregado familiar) on the Portal das Finanças, alongside your tax residence address and preferred service language. This isn't paperwork you can push back: it's the household as it stands on this date, checked against the year-end position, that the AT will use to pre-fill invoices, health and education expenses, and dependant deductions across your entire annual return.

If your household changed during the year — a child turned 18 and stopped studying, custody arrangements shifted, you married or separated — confirming an outdated composition in February can misattribute expenses to the wrong taxpayer or drop a dependant's deduction entirely. Since expenses like invoices are matched to dependants by their NIF throughout the year, getting this declaration right early avoids a scramble when you file the Modelo 3 between April and June.