IBAN Validator

What this tool is used for

• Checking a bank account number from an invoice before setting up a payment.
• Confirming the country and length are consistent with the prefix.
• Validating a batch of supplier IBANs before importing them into a finance system.
• Producing the correctly spaced display form of an IBAN for a document.
• Distinguishing a typo from an account the bank simply does not recognise.

Frequently Asked Questions

How is an IBAN checked?

By the mod-97 algorithm from ISO 13616: move the first four characters to the end, convert letters to numbers (A=10 … Z=35), and the resulting integer must leave a remainder of 1 when divided by 97.

Why mod 97 rather than a simpler checksum?

Because it catches essentially every single-character error and every transposition of adjacent characters — far stronger than Luhn. With a 1-in-97 chance of a random string passing, it is genuinely useful validation rather than a formality.

Are all IBANs the same length?

No, and assuming so is a common bug. Length is fixed PER COUNTRY: Norway is 15 characters, Germany 22, the UK 22, Malta 31. A validator must check the country's own registered length, not a single maximum.

Does a valid IBAN mean the account exists?

No. The checksum proves the digits are internally consistent and the country format is right. Whether the account exists, is open, or belongs to whom you think requires a bank-side check this cannot perform.

Should I store the spaces?

No. Spaces are a display convention in groups of four for readability; the canonical stored form has none. Strip whitespace and uppercase before validating or comparing, or identical accounts compare unequal.

Which countries actually use IBAN?

Most of Europe plus much of the Middle East and parts of the Caribbean — around 80 in total. The United States, Canada, Australia and Japan do not, which is why a payment form asking for an IBAN alone cannot handle a US account.

What is the BBAN inside an IBAN?

The Basic Bank Account Number — the country's own domestic format, wrapped by the country code and the two check digits. Its length and structure vary by country, which is why IBAN lengths range from 15 to 34 characters.

Common errors and gotchas

• Reading a valid checksum as a valid account. Mod-97 catches transcription errors, not fabricated numbers.
• Assuming a fixed length. Each country defines its own, and a correct IBAN can be anywhere from 15 to 34 characters.
• Keeping the printed spaces when submitting, which some systems reject and others silently mangle.
• Confusing the IBAN with the local account number embedded inside it, which is not interchangeable.
• Treating a lower-case IBAN as invalid. It should be normalised to upper case rather than rejected.