An IBAN may contain up to 34 alphanumeric characters and is composed of the following parts:
- Double-digit alphabetic code according to ISO3166
- Two-digit numeric check digit over the whole IBAN under Modulo 97-10 (ISO7064)
- Maximum 30-digit Basic Bank Account Number (BBAN), consisting of the Institute identification (IID) and Bank Account Number (BAN)
The IBAN in electronic form contains no spaces, but in a printed form it is usually presented into groups of four characters with spaces . The last group of characters contains the remaining characters of the IBAN. In this way the IBAN is easier to read. By validating the check digit in the IBAN the frequent cross-border payments misdirections can virtually ruled out. The Basic Bank Account Number is used by the financial institutions identified in the respective countries and the customer account at a bank. The IBAN can be derived, although usually from the domestic bank account number, but it is not always reliable. Therefore the European Committee for Banking Standards (ECBS) has indicated that an IBAN should in principle only be made by the account-holding financial institution. The software-calculation of the IBAN bank account number and ID is not recommended and may lead to incorrect results. A check of the check digit is useful to prevent input errors.
Check digit for IBAN
For the IBAN check digit calculation method, the modulus is used 97-10 (ISO7064). The purely numerical check digit consists of two bodies and is for all participating countries are following the country code at position 3 and 4. In order to calculate and validate the check digit, the alpha characters of the IBAN must be converted using the conversion table below, in double-figures.
|A = 10||B = 11||C = 12||D = 13||E = 14||F = 15|
|G = 16||H = 17||I = 18||J = 19||K = 20||L = 21|
|M = 22||N = 23||O = 24||P = 25||Q = 26||R = 27|
|S = 28||T = 29||U = 30||V = 31||W = 32||X = 33|
|Y = 34||Z = 35|
Swiss Interbank Clearing AG has described an example of the check digit for IBAN. The starting point is the IBAN CH10002300A1023502601. The presentation in paper form would be: CH10 0023 00A1 0235 0260 1. Thus, the check digit is 10. First, the first four characters of the IBAN must be moved to the right end of the IBAN: 002300A1023502601CH10. Subsequently, the alpha characters are converted using the conversion table in numeric characters: 002300101023502601121710. This number is divided by 97. If the check digit is correct, the residual value is always 1.