What it does: DNI, NIE, CIF and IBAN validator
Before adding a client, filling in an invoice or sending a transfer, check that the ID or account is typed correctly. A swapped letter or digit is caught instantly thanks to its check digits.
Paste a DNI, NIE, special NIF, CIF or an IBAN from any country and see whether it's correct, what type it is and, for Spanish accounts, which bank issued it. It also works out a DNI letter and converts old 20-digit accounts to IBAN.
How to use it
- Type or paste the DNI, NIE, CIF, IBAN or account into the main field.
- Read the result: valid or not, the type detected and, if it fails, which character would be right.
- To find a DNI letter, type just the number in “Work out the DNI letter”.
- To check many at once, paste them one per line in “Check a list”.
Examples
DNI letter
For the number 12345678, the remainder when dividing by 23 is 14, which matches the letter Z: 12345678Z.
From an old account to IBAN
The account 2100 0418 45 0200051332 becomes ES91 2100 0418 4502 0005 1332 (CaixaBank).
Limits, formulas and assumptions
- A “valid” ID here only has a consistent format and check digits; it doesn't guarantee it exists or who it belongs to.
- IBANs are checked with the ISO 13616 algorithm (mod 97) and each country's length; Spanish ones also with the account's own check digits.
- The bank name only appears for the most common Spanish banks.
- Nothing is sent: all checks run in your browser.
Frequently asked questions
How is the DNI letter calculated?
The number is divided by 23 and the remainder (0 to 22) picks the letter in the sequence TRWAGMYFPDXBNJZSQVHLCKE. For a NIE, X counts as 0, Y as 1 and Z as 2.
If the IBAN is valid, does the account exist?
Not necessarily: it means there are no copying errors. To know whether it exists and who holds it, you have to ask the bank.
What's the difference between NIF, CIF and DNI?
The NIF is the Spanish tax ID. For Spanish citizens it's the DNI number; for foreigners, the NIE; and for companies it's what used to be called the CIF.
Is it safe to type my details here?
Yes. They are neither stored nor sent: the check happens on your device and disappears when you close the page.