Portuguese NIF Validator

A Portuguese NIF has nine digits and the last one is a control digit computed from the first eight. Multiply them by the weights 9, 8, 7, 6, 5, 4, 3 and 2, add them up, divide by 11 and subtract the remainder from 11: that is the check digit, and if the result is 10 or 11 then it is 0. If the ninth digit typed matches the one computed, the number passes. It is also worth checking the first digit, because only 1 to 9 are assigned: 1 to 4 to individuals, 5 to 9 without the 7 to legal persons, and the 7 to the tax authority. Type the number above and the page does the arithmetic and shows every step.

No, and this is the most important confusion to clear up. The check digit only verifies that the nine digits are internally consistent, which catches a typo but not a deliberate invention. The clearest example is 123456789: the weighted sum is 156, the remainder of dividing by 11 is 2, the check digit is 9, and so the number passes the check without belonging to anyone. The taxpayer register belongs to the Autoridade Tributária, and official confirmation that a NIF exists and is active is obtained from them, on the Portal das Finanças. This page does arithmetic, not a register lookup.

It tells you who the holder is, and it is fixed in law. Digits 1 to 4 belong to individuals (article 4(2) of Decreto-Lei 14/2013), with the particularity that the leading digits «45» belong to non-resident citizens whose only Portuguese income is subject to final withholding tax (article 4(3)). Digits 5, 6, 8 and 9 belong to legal persons and correspond to the NIPC issued by the National Register of Legal Persons, which under article 13(2) of Decreto-Lei 129/98 uses the 5 to 9 range «excluding the digit 7». And the 7 belongs to the tax authority: undivided estates, funds and non-resident entities. The digit 0 is assigned to nobody.

It cannot be, and this is the most useful reading of all. The National Register of Legal Persons is expressly barred from using 7 by article 13(2) of Decreto-Lei 129/98, and the tax authority reserves it for the cases it assigns itself: undivided estates (article 16(2) of Decreto-Lei 14/2013) and the entities of article 11(2), that is non-residents with income subject only to final withholding, funds, and entities with obligations to the tax authority outside the register’s regime (article 11(3)). So if you receive an invoice from a supposed Portuguese company whose NIF starts with 7, either the number was miscopied or the entity is not what it claims to be.

They are the same number seen from two sides. The NIPC is the number the National Register of Legal Persons assigns to an entity when it enters it in the central file of legal persons, and article 11(1) of Decreto-Lei 14/2013 says the NIF of those entities «corresponds to the Legal Person Identification Number (NIPC) assigned by that body». So a Portuguese company does not have a separate NIF and NIPC: it has one nine-digit number, with the same check digit and the same validation. What differs is who assigns it, which is why entities outside the register’s regime, estates, funds, non-residents, get their number straight from the tax authority, in the 7 range.

Because of a detail in the rule. The check digit is 11 minus the remainder of dividing by 11, but 11 minus 0 would be 11 and 11 minus 1 would be 10, and neither is a digit. The convention resolves both cases the same way, making the digit 0. That means two different remainders, 0 and 1, produce the same check digit, while each of the other nine digits comes from a single remainder. The result: 0 appears as a check digit about twice as often as any other digit. It is not a pattern in the numbers issued, it is arithmetic in the rule itself.

It can, yes. Article 78-B(3) of the Personal Income Tax Code is explicit: «acquirers wishing to benefit from the tax credit must require the issuer to include their tax identification number on the invoices.» Paragraph 5 adds that the value of the deductions «is computed by the Autoridade Tributária e Aduaneira on the basis of the invoices reported to it electronically, by the end of February of the year following their issue, in respect of each acquirer identified on them». If the reported NIF is not yours, the expense is attributed to someone else and never appears in your e-fatura. That same paragraph 3 offers a way out for invoices issued without a NIF: the acquirer can report them personally using the QR code or the unique document code.

No. The check runs entirely in your browser, with the arithmetic described above, and the number is not sent to any server or saved anywhere. That is a consequence of how the page is built rather than a policy: there is nothing here that queries a database, because the check-digit arithmetic does not need one.