Check an IBAN

Paste an IBAN to validate its check digits (mod 97), its length for the country and, for a French IBAN, the RIB key. Everything is computed in your browser: the number is sent nowhere.

The calculation runs in your browser: the number you type is not sent to any server.

What this check proves

An IBAN carries two check digits (positions 3 and 4) computed from everything else. If they validate, the number is well-formed: a typo, two swapped digits or a number made up at random fail almost every time.

For a French IBAN the tool also verifies the RIB key (the last two digits), a second, independent check inherited from the French bank account statement.

What it does not prove

That the account exists, is open, or belongs to the company named on the invoice. Vendor-impersonation fraud — an e-mail announcing “new bank details” — uses perfectly valid IBANs: the account simply belongs to the fraudster.

The only check that matters before paying a new IBAN: call the supplier on a number you already had, never the one in the message.

• How to spot a fake IBAN on an invoice: the signals to look for in the document itself.

How to read the result

• Valid check digits, expected length: the number is well-formed — nothing more.
• Invalid check digits: copy the number again from the original document; if it still fails, the IBAN was mistyped or tampered with.
• Unusual length: every country fixes one (27 characters in France, 22 in Germany and the UK, 16 in Belgium); a mismatch means a character was lost or added.

The algorithm in four steps (ISO 13616)

• Move the first four characters (country and check digits) to the end.
• Replace every letter with a number: A = 10, B = 11 … Z = 35.
• Take the remainder of the resulting large number divided by 97.
• The remainder must be 1. For a French IBAN, the RIB key must equal 97 minus the remainder of “bank, branch, account” × 100 divided by 97.

Check the whole invoice, not only the IBAN

TrustyFile runs this check on the IBANs found in a PDF, then looks for what a valid IBAN will never tell you: a covered amount, a revision added afterwards, hidden text, a company identifier the registry does not know.

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