The rules vary to a great extent between the countries. To overcome these difficulties, the European Committee for Banking Standards (ECBS) developed the IBAN which was later adopted as an international standard under ISO 13616:1997. Since the IBAN error detection uses mod 97, it will trap all such errors.
Before IBAN, users, especially individuals and small businesses (SMEs), used to be confused by the differing national standards for bank account identification such as bank, branch, routing codes and account number. Does the BBAN format follow the format specified for this country?