The International Bank Account Number (IBAN) is an international standard for identifying bank accounts across national borders in a way that would minimise the risk of propagating transcription errors. The IBAN was originally developed to facilitate payments within the European Union but the format is flexible enough to be applied globally. It is up to each country's national banking community to decide on the length of the BBAN for accounts in that country, but its length must be fixed for any given country.
The Spanish IBAN is constructed as below, with a total of 24 characters :
ESkk BBBB GGGG KKCC CCCC CCCC
G = Branch/office number
K = Check digits
C = Account No.