Background Information on IBANs

Standard domestic account number systems exist in most countries. The IBAN is not a single account number structure to replace these. Instead, it is a way of representing existing account numbers in a standard recognisable format, which can be verified using mathematically calculated check digits. To make a cross border European payment, customers will need to quote an IBAN and its associated Bank Identification Code (BIC) in the same way they currently quote an account number and a BIC.  

An IBAN consists of a header placed in front of a country's normal domestic account number format. This header consists of a two character country code followed by a pair of check digits. In the United Kingdom, and in some other countries, a code (the first four characters of the BIC) has been incorporated in front of the standard domestic account to clearly identify the issuing bank. 

The country code enables recognition of the country in which the IBAN was issued. It also indicates the national account structure to be used when deciphering the domestic account number contained within the IBAN.

Example of a UK IBAN:

The check digits are calculated by the financial institution issuing the IBAN, using a formula applied to the whole IBAN. There is a formula by which any party can perform an integrity check on an IBAN that has been quoted to them. 

Please note that the use of the IBAN validator does not guarantee that the bank code and account number are correct, nor does it guarantee that the account actually exists or is live. It checks that the characters/numbers have not been accidentally transposed.