Portugal NIF Validator
Online Portuguese NIF (Tax Number) validator. Verify compliance with official AT constraints.
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How does Portuguese NIF validation work?
Validation checks if the NIF has exactly 9 digits, starts with a valid category prefix, and computes a Modulo 11 sum of the first 8 digits using decrescent weights from 9 to 2.
If the weighted sum % 11 is 0 or 1, the check digit must be 0. Otherwise, it is 11 minus the remainder. Any discrepancy marks the document as invalid.