IBAN Number

An IBAN (International Bank Account Number) is composed of 14 to 34 characters according to standard ISO13616.

It starts with 2 letters indicating the country code of the bank account, then the checksum control key (between 02 and 98) and from 10 to 30 characters depending on countries that usually identify the bank and the account number.

An IBAN number is made up of a series of letters and numbers (14 to 34 characters depending on the country) described in the ISO13616 standard.

It begins with 2 letters indicating the country code of the bank account, followed by the IBAN checksum (between 02 and 98) and 10 to 30 characters depending on the country which correspond to bank codes including the bank account number.

The algorithm checks the country code first among countries accepting IBAN (ISO-13616 norm).

The algorithm starts by moving the 4 first characters (country code and checksum key) at the end of the IBAN and set the key to 2 digits 00.

Replace each letter in the IBAN by its rank in the alphabet + 9. So A=10, B=11, C=12, etc. Z=35

Calculate the value of this big number modulo 97 and subtract the result to 98 in order to get the control key.

Check if the two 2 characters after the country code are 51, if yes the IBAN passes validation.

It may be envisaged to perform the verification of the existence of the bank code and the account number, this operation requires adequate databases.

The IBAN is generally present on bank identity statements (RIB), but also often on checkbooks or other bank statements.

It is important to note that the IBAN is specific to each bank account, several accounts therefore mean several distinct IBANs.

Sometimes it is asked to concatenate both IBAN and BIC codes (IBAN+BIC or BIC+IBAN).

The IBAN identifies a specific bank account, while the BIC (Bank Identifier Code) or SWIFT (Society for Worldwide Interbank Financial Telecommunication) is used to identify the bank itself.

It is common for the two to be used together.

A possible source code for programming the checksum calculation is // Pseudo code
function calculateIBANChecksum(iban) {
rearrangedIBAN = iban[4..] + iban[0..1] + "00"
numericIBAN = ""
for each character in rearrangedIBAN {
if (character is a letter) numericIBAN += ASCII code of (character) - 55
else numericIBAN += character
}
checksum = 98 - (numericIBAN % 97)
return checksum
}