NIF for minors and families: one number per child

One number per child, for life

The first thing to get straight is that a NIF belongs to a person, not to a household. Parents sometimes ask for a family NIF, or assume a child is covered by a parent's number until they turn 18. Neither is how it works. Each child is issued their own nine-digit number, and that number never expires and never changes, even if the family leaves Portugal and returns years later. It is the same permanent number adults get, and it follows the child into adulthood, when they start managing their own tax affairs under it.

That permanence is also why it is worth getting children's numbers sorted early rather than treating them as an afterthought to the parents' applications. School enrolment, health registration, visa files, and the parents' tax return all ask for the child's number at different points in a move. A child whose number is already issued never holds up any of those steps. A child whose number is still pending can hold up all of them at once, usually in the same week the family is trying to settle.

Where a child's NIF actually gets used

The most immediate use is school. A child's NIF is commonly requested at enrolment, and having it ready means one less document chase in the first weeks after arrival. Be clear about one thing, though. Portugal's enrolment rules say the child's NIF is provided if one has already been assigned, so a missing number is a delay, not a closed door. Do not let anyone tell you a child cannot start school without a number they have not been issued yet. Get the number, and hand it over when asked.

Health registration is the second use. A child needs their own number in their own health file, and the same goes for a bank account opened in the child's name where the bank offers one. The third use is immigration paperwork. Family reunification files list each child, and a child's NIF belongs in that file alongside the birth certificate. The fourth use, and the one with money attached, is the parents' IRS return, which gets its own section below. None of these uses requires the child to have income, a job, or any tax bill. A NIF is an identifier first, and most children with one will owe nothing under it for years.

The documents, child by child

For a child with a passport, the file looks much like an adult file. The child's passport proves identity, the parent's ID proves who is acting for the child, and proof of address covers where the family lives. Proof of address usually means a utility bill, a bank statement, or a rental agreement, and for a family filing from abroad it is the foreign address, dated within the last three months. One parent's address is normally enough for the whole family file, which is one more reason to file together.

For a child under 10 without a passport, a birth certificate stands in for the passport. That is the single most useful sentence on this page, because it is the document parents most often fail to bring. Older children without a passport are a harder case, and the honest advice is to get the passport first rather than argue the point at a tax office counter. A birth certificate also does a second job in every child's file: it proves the parent relationship. That matters when a child's surname differs from the filing parent's surname, and it matters more when custody is shared and only one parent is doing the filing. If the birth certificate is not in English, Spanish, French, or Portuguese, services report that a certified translation is needed, and foreign-issued documents may also need an apostille. Get the translation done before filing, not after a rejection. For the translation and apostille rules in full, see our NIF documents checklist.

Why both parents sign the power of attorney

When a representative files for a child, both parents sign the power of attorney. That is the rule services apply in practice, and it catches families by surprise because an adult application needs only one signature. The reason is straightforward. A child cannot consent for themselves, so the tax authority wants the authorisation to come from both people with parental responsibility, not just the one who happened to fill in the form. The same document authorises the representative to request the number, and it should also explicitly grant fiscal representation powers if the same person is to stay on as the child's representative afterwards. Filing and representation are two different jobs, and a form that covers only the filing does not cover the second job.

Single parents and legal guardians are the exception to plan for, not a reason to panic. If one parent holds sole custody, or a guardian rather than a parent is filing, the file needs the document that proves it: a custody order, a guardianship document, or an adoption certificate. Bring that document instead of a second signature, and tell the service about it before filing so it can check the paper rather than reject the file for a missing signature. If one parent genuinely cannot sign, ask the service what it accepts in place of that signature before you pay. Do not assume a single signature will slide through, because a rejection costs the same 3 to 5 days per round as an adult rejection, and a family filing has more rounds to lose. For how long each route takes, see our NIF processing time guide.

File the whole family together

Filing everyone at once is the single best piece of practical advice on this page. It keeps the address record consistent across the family, so the tax authority holds the same address for parents and children instead of slightly different versions filed months apart. It also means one round of document gathering, one power of attorney session, and one timeline to track, rather than a second project starting just as the first one finishes. Parents who file their own numbers first and add children later almost always wish they had done it in one pass.

Budget for it properly. Most online services charge per person, and children usually count as full applicants, even though their files are simpler. That surprises families who assumed children would be free or half price, and it turns a two-adult quote into a four-person bill. Some services discount family files, so ask for the whole-family price in writing before paying, and check whether the portal password is included for each child or charged as an add-on per applicant. For what each route costs in total, see our NIF cost guide and our NIF services comparison.

The IRS payoff: why the numbers earn their keep

A child's NIF pays for itself on the parents' IRS return. Each child listed as a dependent carries a fixed deduction of €600, rising by €126 for a child under three, under the 2026 rules. On top of that fixed amount, health spending for the household deducts at 15 percent up to a €1,000 household cap, and education spending deducts at 30 percent up to an €800 household cap. Those caps are per household, not per child, so a second child does not double them, but the fixed €600 per dependent applies for each child. None of it is claimable without the child's number on the return, which is why the number belongs on the file before the first tax year ends, not after.

The habit that protects the deductions is dull but valuable. Give the child's NIF when paying for things that belong to the child, such as doctor visits, prescriptions, and school costs, so the invoices land in the right place in the e-fatura system. Parents who pay for everything under their own number and sort it out at filing time create exactly the reconciliation mess the system is designed to avoid. Children can also stay on a return as dependents into young adulthood while they are in full-time education, under the usual rules up to age 25, so a teenager's number keeps working for the family long after the move itself is forgotten.

When a child needs a representative of their own

Most children never need a fiscal representative. A child with no Portuguese tax ties of their own has nothing for a representative to represent, and the parents' own arrangements cover the family. The exception is a minor with tax ties in their own name, and the usual example is inherited property. A child who inherits a house in Portugal has a tax relationship with the Portuguese state in their own right, and that relationship needs its own representative appointment, made by a parent. The appointment is the child's, even though a parent arranges and pays for it, and it is separate from the parents' appointments for their own numbers.

The same 15-day logic that applies to adults applies here: once the tax relationship begins, the appointment or an electronic notification channel should be in place within 15 days. In practice, the family lawyer handling the inheritance usually raises it, but do not assume that. Ask directly who is appointing the child's representative, and confirm the appointment is registered before the first property tax bill falls due. For the general rules on who needs a representative and what one costs, see our fiscal representative guide and our guide to getting a NIF without a representative.

The mistakes families make

The first mistake is assuming one family number exists. It does not, and every form that asks for the child's number will keep asking until the child has one. The second mistake is filing children at different addresses from their parents, which happens when one parent files from an old address and the other files later from the new one. File together, at one address, and the record stays clean. The third mistake is the single-signature power of attorney described above. The fourth mistake is waiting until a visa appointment or a school deadline to start, when a rejection round would still leave time to fix it. Start the children's files with the parents' files, not after them.

The fifth mistake is subtler, and it costs money rather than time. Families pay for representation for children who do not need it, year after year, because nobody told them a child without tax ties needs no representative of their own. Check each child's position separately. A child with inherited property needs an appointment. A child with no property, no car, no job, and no self-employment in Portugal does not. Paying for the second child's representation is paying for a service with nothing to do, and it is the easiest saving in the whole family file.

What to do, in order

Start by listing every child who needs a number, including children who will join the family later through reunification, so nobody is discovered at the last minute. Gather each child's passport or birth certificate, the filing parent's ID, and proof of address, and get any translation done before filing. If a representative is filing, get both parents' signatures on the power of attorney, or the custody or guardianship document that stands in for the second signature. File the whole family together, confirm each number when it arrives, and put each child's number on the parents' IRS return from the first tax year.

Two short primers close the gaps this page deliberately leaves open. A company does not get a personal NIF at all. It gets its own company tax number when it is incorporated, and every director and shareholder still needs a personal NIF first, so children's numbers are never the blocker on a company file, but parents' numbers are. And when the family moves, the address on every family member's number needs updating, children included, so an address change filed for the parents alone leaves the children's records pointing at the old address. Our guide to address changes for the whole family covers each move and its deadline. For the filing steps and the full document rules behind this page, our guide to getting a NIF online and our NIF documents checklist carry the detail.