How is the NIF check digit calculated?

Multiply each of the first eight digits by the weights 9, 8, 7, 6, 5, 4, 3, 2 in order. Sum the products, then take the remainder of that sum divided by 11. The control digit is 11 minus the remainder; if the result is 10 or 11 it becomes 0. The 9th digit of the NIF must equal this control digit.

Does a valid result mean the NIF actually exists?

No. The tool confirms only that the format and mod-11 check digit are correct. A structurally valid NIF is not guaranteed to have been assigned by the Autoridade Tributária e Aduaneira (AT) — only AT can confirm a number is live. Think of it as a spell-checker, not a registry lookup.

What does the leading digit of a NIF tell you?

The first one or two digits encode the taxpayer class. Examples: 1, 2, 3 are individual persons; 5 is a corporate entity; 6 is a public-sector body; 71 is a non-habitual resident (NHR); 72 is an investment fund; 90 or 91 is a condominium or cooperative. The tool labels all recognised prefixes automatically.

What is the difference between a NIF and a NIPC?

A NIF (Número de Identificação Fiscal) identifies an individual taxpayer, while a NIPC (Número de Identificação de Pessoa Colectiva) identifies a legal person such as a company. Both are 9 digits and share the same mod-11 check-digit rule, so this validator handles both identically.

Is the NIF the same as a Portuguese VAT number?

Yes. For businesses, the Portuguese VAT number is simply the NIF/NIPC, often prefixed with the country code PT when used in EU VAT contexts — for example PT545259045. The numeric part (without PT) is what this tool validates.

Why can the check digit be 0 when the remainder is 1 or 0?

When 11 minus the remainder equals 10 or 11, neither is a valid single decimal digit, so the standard defines the check digit as 0 in both cases. This means check digit 0 is genuinely valid for some NIFs — it is not an error or a placeholder.

Portugal NIF Validator

A Portuguese NIF (Número de Identificação Fiscal) is the 9-digit tax identification number assigned to every taxpayer in Portugal — individuals, companies, public bodies, investment funds, and sole traders all share the same format. It is also the foundation of the NIPC (Número de Identificação de Pessoa Colectiva) used for legal entities. Whether you are building an invoicing system, validating user input on a checkout form, or cross-checking a supplier’s fiscal number, a reliable NIF validator is essential.

This tool implements the official mod-11 check-digit algorithm used by the Autoridade Tributária e Aduaneira (AT). It runs entirely in your browser — the number never leaves your device — and it shows you the full step-by-step calculation so you understand exactly why a NIF passes or fails.

How the mod-11 algorithm works

Every NIF has nine digits. The first eight carry the actual identifier; the ninth is a check digit computed from them. The algorithm is:

weights  =  9   8   7   6   5   4   3   2
digits   =  d1  d2  d3  d4  d5  d6  d7  d8   d9(check)

sum      = (d1×9) + (d2×8) + (d3×7) + (d4×6)
         + (d5×5) + (d6×4) + (d7×3) + (d8×2)

remainder = sum mod 11
control   = 11 − remainder
if control >= 10 → control = 0

d9 must equal control

The validator displays every intermediate value — the weighted sum, the remainder, and the expected versus actual check digit — so a single mistyped digit is easy to pinpoint.

Entity-type prefix table

Prefix	Taxpayer class
1, 2, 3	Individual person (pessoa singular)
45	Non-resident individual
5	Corporate entity (pessoa colectiva)
6	Public-sector body
70, 74, 75	Inheritance / special non-resident
71	Non-habitual resident (NHR scheme)
72	Investment fund
77	ATM special attribution
78	Non-resident (other)
8	Sole trader / ENI (historic)
90, 91	Condominium or cooperative
98	Non-resident without NIF

Worked example with a fake NIF

Take the obviously-fake number 545259045 (chosen so it does not correspond to any real taxpayer):

Digits 1–8: 5 4 5 2 5 9 0 4
Weighted sum: 5×9 + 4×8 + 5×7 + 2×6 + 5×5 + 9×4 + 0×3 + 4×2 = 45+32+35+12+25+36+0+8 = 193
Remainder: 193 mod 11 = 6
Control: 11 − 6 = 5
9th digit: 5 — matches, so the check digit passes
Prefix 5 → Corporate entity (pessoa colectiva)

Paste that number into the tool above to see the identical breakdown live.

Privacy and limitations

Every calculation happens locally. No NIF you enter is transmitted to any server. The tool confirms structural validity only — it cannot tell you whether a NIF has been assigned by AT or whether the associated taxpayer is currently active. For authoritative confirmation, use the AT online portal or the VIES system for EU VAT cross-border queries.