IBAN Number

IBAN, or International Bank Account Number, is an international bank account number used to uniquely identify a bank account worldwide.

IBAN facilitates cross-border financial transactions and reduces the risk of errors in processing international payments.

An IBAN number is made up of a series of letters and numbers (minimum 14 to maximum 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.

An IBAN is validated by 5 independent tests (ISO-13616 norm, SWIFT registry of 89 countries). The result of each test is displayed with a checked (passed) or unchecked (failed) box.

Before any test, the IBAN is normalized: spaces and separators are removed and lowercase letters are converted to uppercase.

— Country: the first 2 letters must be a country code from the IBAN registry.

— Size: the total length must match the one defined for the country.

— Fixed check (only for some countries): in 9 countries (BA, ME, MK, MR, PT, RS, SI, TL, TN), the IBAN key has an imposed value (for example 50 for Portugal, 56 for Slovenia), because the account number already carries its own national check digits computed with modulo 97.

— BBAN format: after the country code and the key, the remainder of the IBAN (the BBAN, the national account number) must follow the country's format, made of digits (n), letters (a) or alphanumeric characters (c).

— Check digits: this is the modulo 97 calculation below.

a) Move the 4 first characters (country code and key) to the end of the IBAN, replacing the key with 00.

b) Replace each letter by its rank in the alphabet + 9. So A=10, B=11, C=12, etc. Z=35. Letters can appear in the country code as well as in the account number.

c) Calculate the value of this big number modulo 97, then subtract the result from 98 to get the check key. The number exceeds the capacity of ordinary integers, so pay attention to process it in chunks or with a big number library.

d) Check that the 2 characters after the country code are this key. Here, FR14: the IBAN passes validation.

Validation guarantees that an IBAN is well formed, not that it exists. Verifying the existence of the bank code and the account requires adequate databases (and the bank's agreement).

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.

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.

No, the first 2 letters indicate the country, immediately foreign IBANs are distinct and recognizable.

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

The IBAN is not considered highly confidential information, as it is necessary to receive transfers.

However, avoid sharing it unnecessarily and remain vigilant against phishing or scam attempts.

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
}