NIF Validator - Validate Portuguese Tax Identification Numbers

Validate Portuguese NIF numbers instantly with Modulo 11 checksum verification

Enter the 9-digit NIF. Only digits are accepted.

Enter a NIF number above to validate

NIF Format Reference

Portuguese NIFs follow a specific 9-digit format defined by the Tax and Customs Authority (AT).

Format Structure

NIFs are 9 plain digits. The last digit is a Modulo 11 check digit.

XXXXXXXXX

Taxpayer Categories

The first digit identifies the taxpayer type: 1-2 (natural persons), 3 (natural persons), 5 (public entities), 6 (local authorities), 7 (inheritable estates), 8 (irregular companies), 9 (other).

NIF Validation Rules

  • Must be exactly 9 digits long
  • First digit must be 1-3 or 5-9
  • Last digit must satisfy the Modulo 11 checksum

About NIF Validator

NIF Validator verifies Portuguese NIF (Número de Identificação Fiscal) numbers using the official Modulo 11 algorithm and identifies the taxpayer type from the first digit. This tool validates format compliance, checksum accuracy, and provides taxpayer category information.

Validate NIF numbers with instant verification of the 9-digit format and Modulo 11 check digit using the official Portuguese tax authority algorithm. The tool automatically identifies the taxpayer category (individual, company, public entity, etc.) based on the first digit.

Essential for form validation in Portuguese applications, e-invoicing systems, tax compliance platforms, banking KYC applications, and any system requiring NIF validation. Perfect for developers building applications that serve Portuguese users or process Portuguese fiscal data.

Instant Modulo 11 validation catches common data entry errors before processing. Taxpayer type identification helps with compliance workflows, while complete privacy protection ensures sensitive fiscal data never leaves your device.

Key Features

  • Official Modulo 11 algorithm validation
  • Taxpayer type identification from first digit
  • 9-digit format validation
  • Instant feedback with specific error messages
  • Complete client-side privacy protection
  • No server requests - works offline

NIF Validator Frequently Asked Questions

How accurate is the NIF validation?

Our validator uses the official Modulo 11 algorithm used by the Portuguese Tax and Customs Authority (AT). It checks format compliance and verifies the check digit with 100% algorithmic accuracy. However, it does not verify if a NIF is registered with AT.

What is a NIF?

A NIF (Número de Identificação Fiscal) is a 9-digit Portuguese tax identification number. It is assigned to natural persons and legal entities for tax purposes. The check digit is calculated using the Modulo 11 algorithm.

What taxpayer types are identified by the first digit?

First digit 1-2: Natural persons; 3: Natural persons (some cases); 5: Public legal entities; 6: Local authorities; 7: Inheritable estates; 8: Irregular companies; 9: Final consumers or foreign entities. Digits 4, 0 are not assigned.

Is my NIF data secure when using this validator?

Absolutely. All validation happens entirely in your browser using JavaScript. No NIF data is ever sent to our servers. Your data never leaves your computer.

Can I use this for legal verification?

No. Our validator only checks mathematical validity. For legal purposes or official transactions, verify NIF registration with AT (Autoridade Tributária e Aduaneira) through official channels.

NIF Validation Best Practices

  • Always validate NIF on both client and server sides
  • Store NIF without formatting (9 plain digits) in databases
  • Never store or log NIF numbers unnecessarily
  • Follow GDPR requirements when handling NIF data
  • Validate first digit to distinguish taxpayer category

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