What Is an IBAN? International Bank Account Number Format, Check Digit Rules, and Which Countries Use It

An IBAN (International Bank Account Number) is a unified bank account numbering format defined by the ISO 13616 standard. Its purpose is to let cross-border payment systems validate the account structure at the point of initiation, reducing returns caused by account number errors. An IBAN is at most 34 characters long and has three parts: a 2 letter country code (DE for Germany, FR for France, GB for the United Kingdom), 2 check digits, and the rest is the country-specific BBAN (basic account number, which usually encodes the bank code, branch code, and account number). A German IBAN, for example, is 22 characters in total: DE, then 2 check digits, then an 8 digit bank code, then a 10 digit account number.

An IBAN is not a new account; it is the international way of writing an existing one. The same German account might be written as just a bank code plus account number domestically, and as an IBAN for cross-border use. Both point to the same account.

Characters 3-4 of an IBAN are check digits computed with the ISO 7064 MOD 97-10 algorithm: move the country code and check digits to the end, convert letters to numbers, and take the result modulo 97; only a remainder of 1 makes a valid IBAN. This means that a mistyped, missing, or transposed character will, in the vast majority of cases, be caught immediately by the algorithm, so online banking and remittance systems can block the error before submission.

Keep in mind that the check digits only prove the format is valid, not that the account exists and belongs to the intended beneficiary. An IBAN that passes validation could still be a closed account or someone else's account, so verifying that the beneficiary name matches the account before paying remains necessary. The EU's Instant Payments Regulation, phased in from 2024, requires banks to offer beneficiary name checking (Verification of Payee) precisely to close this gap.

The IBAN registry is maintained by SWIFT on behalf of ISO and covers more than 80 countries and territories: the entire European Economic Area (mandatory for euro payments within SEPA), the United Kingdom, Switzerland, several Middle Eastern countries (the UAE, Saudi Arabia, and others), and some African and Latin American countries. Each country's IBAN length is fixed; the authoritative length table is the IBAN Registry published by SWIFT.

Just as important is where IBANs are not used: the United States, Canada, mainland China, Hong Kong, Singapore, Japan, Australia, New Zealand, and other major economies do not use them. When sending money to these places, an IBAN is neither needed nor exists; supply the local account number (together with a BIC, routing number, or local clearing code). If a form insists on an IBAN field, confirm with the beneficiary bank how to fill it in rather than fabricating a number that merely looks like one.

In corridors that use IBANs, the IBAN locates the account within the bank, and the BIC locates the bank on the network. For payments within SEPA, most scenarios now require only the IBAN (the IBAN-only rule), since systems can derive the routing from it; but cross-border wires outside SEPA usually still require the IBAN and BIC together. When filling in a form, make sure both belong to the same entity of the same bank: a mismatch between the IBAN's country segment and the BIC's country code is one of the errors most likely to get a payment held for investigation at an intermediary bank.