What Is an IBAN? Structure, Length, and Check Digits
An International Bank Account Number (IBAN) identifies a bank account across borders. It is a two-letter ISO 3166-1 country code, two ISO 7064 MOD-97 check digits, and a country-specific Basic Bank Account Number (BBAN).
Updated 2026-09-30 · 5 min read
What an IBAN is
An IBAN, or International Bank Account Number, is a single string that identifies a bank account and the country it is held in. ISO 13616 defines the format; the SWIFT IBAN Registry records the structure each country uses.
An IBAN is issued by the account-holding bank. It is not a card number, a routing number, or proof that an account exists — it is an agreed format for writing an account identifier so that cross-border payments can be routed without ambiguity.
How an IBAN is structured
Every IBAN has three parts, in this order: the two-letter ISO 3166-1 alpha-2 country code, two check digits computed with ISO 7064 MOD-97-10, and the country-specific Basic Bank Account Number (BBAN).
The BBAN is where countries differ. It embeds a bank identifier, sometimes a branch identifier, and the account number, but the length and position of each field are set nationally, not internationally.
| Country | IBAN length | BBAN pattern | Example |
|---|---|---|---|
| Germany (DE) | 22 | 18n | DE89 3704 0044 0532 0130 00 |
| United Kingdom (GB) | 22 | 4a 14n | GB82 WEST 1234 5698 7654 32 |
| Norway (NO) | 15 | 11n | NO93 8601 1117 947 |
| France (FR) | 27 | 10n 11c 2n | FR14 2004 1010 0505 0001 3M02 606 |
Why IBAN lengths differ
IBANs run from 15 characters (Norway) to 34 (the ISO 13616 maximum). The country code alone does not determine the length; a validator must use the registry entry for that country.
A string that starts with a valid country code can still be the wrong length. Length checking is a structural rule, separate from the checksum rule.
- Shortest registered IBAN: 15 characters (Norway).
- Longest permitted IBAN: 34 characters (ISO 13616).
- The IBAN is fixed-length per country — there is no optional suffix.
The check digits
Characters 3 and 4 are a MOD-97-10 checksum over the whole IBAN. The algorithm catches single-character typos and most transpositions before a payment is sent.
A checksum pass means only that the string is internally consistent. It does not confirm that the account exists, is open, or belongs to the name you hold.
What an IBAN does not tell you
An IBAN contains no account holder name, no balance, and no payment status. Those live with the bank and are resolved by the payment scheme, not by the number.
For that reason, IBAN validation is a format and checksum check, not a verification of ownership or of the ability to receive funds.
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Open the toolFrequently Asked Questions
IBANs are 15 to 34 characters, fixed per country. Norway is the shortest at 15; the ISO 13616 maximum is 34. Always check the length against the country registry entry rather than assuming.
The first two characters are the ISO 3166-1 alpha-2 country code, such as DE for Germany or GB for the United Kingdom. Characters 3 and 4 are the check digits.
No. A valid IBAN only passes the structure and MOD-97 checksum rules. It does not confirm that the account is open, that it belongs to a given name, or that it can receive a payment.
No. An IBAN identifies the account; a BIC (also called a SWIFT code) identifies the bank. Cross-border payments commonly need both.