How long is a UK IBAN?

A UK IBAN is exactly 22 characters — GB, two check digits, a 4-letter bank code (the first four of the bank BIC), a 6-digit sort code and an 8-digit account number.

Does the UK IBAN contain my sort code?

Yes. Characters 9–14 are the 6-digit sort code and the final 8 characters are the account number, which is why the IBAN can be derived directly from domestic details.

Is there an extra national check digit?

The UK IBAN itself relies on the MOD-97 checksum. The separate modulus-check tables banks use for sort code and account verification are not embedded in the IBAN.

Is my IBAN sent anywhere?

No. The MOD-97 calculation runs locally in your browser. Nothing is uploaded, stored or logged.

UK IBAN Validator — Gera Tools

Validate a UK IBAN in your browser

A UK IBAN is the 22-character form of a British bank account used for international (and SEPA) payments. It packages the familiar 6-digit sort code and 8-digit account number together with a 4-letter bank code. This tool checks the structure and the ISO 7064 MOD-97-10 checksum, all on your device.

How it works

The UK IBAN layout is GB + 2 check digits + 4-letter bank code + 6-digit sort code + 8-digit account number.

To verify the checksum (ISO 7064 MOD-97-10):

Strip spaces, uppercase, and confirm the IBAN starts with GB and is 22 characters.
Move the first four characters (GB + check digits) to the end.
Replace each letter with two digits — A = 10 up to Z = 35 — so G becomes 16 and B becomes 11.
Take the resulting number modulo 97; a valid IBAN gives exactly 1.

The tool also confirms the bank code is four letters and that the sort code and account number are the correct number of digits, then displays the sort code in the familiar NN-NN-NN form.

Example and notes

The sample IBAN GB29 NWBK 6016 1331 9268 19 has bank code NWBK (NatWest), sort code 60-16-13 and account 31926819. A passing MOD-97 result proves the IBAN is internally consistent and catches most typos, but UK banks additionally run modulus-checking on the sort code and account number to confirm the combination is genuinely issuable — that is separate from the IBAN checksum and from whether the account is actually open.