NIF Checker Guide – Easily Verify Portuguese Tax Numbers

What is a NIF Number?

NIF (Número de Identificação Fiscal) is Portugal’s taxpayer identification number, issued by the Tax and Customs Authority (AT). It consists of 9 digits: the first digit indicates the taxpayer type (1‑5 for individuals; 5 for non‑residents; 6, 8, 9 for companies). The last digit is a check digit calculated using the mod‑11 algorithm (weights from the second to the second‑last digit). This number is used for tax filings, invoicing, bank account opening, and more.

How to Use This NIF Checker

1. Enter a 9‑digit number (input is automatically restricted to digits).
2. Click “Validate” – the tool will verify the first digit’s validity and the mod‑11 checksum.
3. View the result instantly.

This tool is completely free, ideal for accountants, cross‑border e‑commerce, and anyone dealing with Portuguese business entities.

Frequently Asked Questions

1. Does the NIF Checker guarantee the number actually exists?

This tool validates the format and checksum. A valid result means the number is mathematically correct. To confirm real‑world assignment, you must consult the Portuguese tax authority.

2. Why does my NIF show as invalid?

Possible reasons: length is not 9 digits; first digit is not allowed (1‑5 or 6‑9 allowed); or the check digit does not match. The calculation: multiply the first 8 digits by weights 9,8,7,6,5,4,3,2 respectively, sum them, take mod‑11. If the remainder is 0 or 1, the check digit is 0; otherwise, it’s 11 minus the remainder.

3. Can non‑Portuguese companies get a NIF?

Yes, non‑Portuguese entities operating in Portugal must apply for a NIF (temporary or permanent) to conduct business.

Have more questions? Feel free to reach out. Thanks for using our NIF Checker!