What is an IBAN Number? How International Bank Account Numbers Work

An IBAN (International Bank Account Number) is a standardized format for identifying bank accounts across national borders. Developed by the International Organization for Standardization (ISO 13616) and the European Committee for Banking Standards, IBANs make cross-border payments faster, cheaper, and less error-prone. This guide explains the structure, validation, and usage of IBANs worldwide.

IBAN Definition

An IBAN is an alphanumeric string of up to 34 characters that uniquely identifies a bank account for international transactions. It combines the country code, check digits, and the domestic bank account number (called the BBAN) into a single, globally recognized format.

IBANs were created to solve a real problem: every country had its own account numbering system, making cross-border transfers slow, expensive, and error-prone. With IBANs, a bank in Germany can instantly validate and route a payment to a bank in Spain without manual intervention.

IBAN Structure Breakdown

Every IBAN consists of four parts:

The BBAN (Basic Bank Account Number) is everything after the check digits — it includes the bank code, branch code, and account number in a format specific to each country.

How IBAN Validation Works (MOD-97)

IBANs are validated using the MOD-97 algorithm defined in ISO 7064. This catches typos and transcription errors before a payment is sent. The validation process works as follows:

1. Move the first four characters (country code + check digits) to the end of the IBAN
2. Convert letters to numbers using A=10, B=11, C=12, ... Z=35
3. Calculate the remainder when dividing the resulting number by 97
4. If the remainder is 1, the IBAN is valid. Any other result means the IBAN contains an error

This validation can detect single-character errors with near-100% accuracy. It also catches most transposition errors (swapping two adjacent characters). Banks perform this check before processing any international transfer.

IBAN vs SWIFT/BIC

People often confuse IBANs and SWIFT codes, but they serve different purposes:

For international transfers, you typically need both — the SWIFT code routes the payment to the correct bank, and the IBAN ensures it reaches the correct account.

Which Countries Use IBANs?

IBANs are mandatory for cross-border payments in the SEPA zone (European Union + EEA) and are used in over 80 countries worldwide. The IBAN length varies by country:

Notable Countries That Do NOT Use IBANs

• United States — uses ABA routing numbers + account numbers domestically, SWIFT for international
• Canada — uses transit numbers + institution numbers + account numbers
• Australia — uses BSB (Bank-State-Branch) codes + account numbers
• Japan — uses bank codes + branch codes + account numbers
• China — uses CNAPS codes for domestic transfers
• India — uses IFSC codes + account numbers

How to Find Your IBAN

If your country uses IBANs, you can find yours in several places:

• Online banking — check your account details or settings page
• Mobile banking app — usually under "Account Info" or "Account Details"
• Bank statements — printed on monthly or quarterly statements
• Debit/bank cards — some banks print the IBAN on the back of the card
• Bank branch — ask a teller or use the self-service terminal
• Customer service — call your bank's helpline and request it

Common IBAN Mistakes

• Including spaces in electronic submissions — IBANs are displayed with spaces for readability (GB29 NWBK...) but should be entered without spaces in payment systems
• Confusing O (letter) with 0 (zero) and I (letter) with 1 (one) — IBANs never contain the letters O or I to avoid this confusion
• Using the wrong country format — a German IBAN has 22 characters, a French one has 27. If the length is wrong, the IBAN is invalid
• Omitting the country code — the two-letter country code at the start is mandatory
• Transposing digits — swapping two adjacent digits produces an invalid IBAN (caught by MOD-97 validation)

Frequently Asked Questions