About Check and Validate

Check and Validate is a small, free set of tools for checking bank, tax, card, and identity numbers. It covers a growing range of them: the IBAN, UK VAT numbers, credit card numbers (using the Luhn check), the Spanish DNI and NIE, UK driving licences, the Romanian CNP, and the ISBN. Each tool runs the official algorithm for that number and explains, in plain language, whether it is well formed and why.

Why this site exists

Numbers like these are easy to mistype and annoying to get wrong. A single swapped digit in an IBAN can bounce a payment, and a mismatched letter on a DNI can get a form rejected. Most of the checkers we could find were cluttered, buried the answer under ads, or quietly sent the number to a server. We wanted something faster and clearer: paste a number, get a straight answer, and understand the reasoning behind it.

How the tools work

Every calculation happens in your browser. When you check any of these numbers, whether a card number, an IBAN, or an ID document, the digits never leave your device. Nothing is uploaded, stored, or logged, so it is safe to check a real number. Because the logic runs locally, the tools also work if your connection drops after the page has loaded.

What the tools do not do

These are format and checksum validators, not official databases. A result of valid means the number is mathematically consistent and correctly structured. It does not mean the number was ever issued, belongs to a specific person, or points to an open account. Only the issuing authority or the relevant bank can confirm that.

A note on languages

Check and Validate is published in English, Romanian, and Spanish. Each version is written in that language rather than machine translated, and the language links in the header always take you to the same tool in your chosen language. If you spot a wording that reads awkwardly in any language, we would like to hear about it.

Contact

Questions, corrections, and suggestions are welcome at contact@checkandvalidate.com. There is more detail on the contact page.