IBAN (International Bank Account Number) is an internationally standardized system for identifying bank accounts across national borders. Developed by the International Organization for Standardization (ISO 13616) and the European Committee for Banking Standards, IBANs help reduce errors in cross-border transactions. Each IBAN contains a country code, two check digits, and a Basic Bank Account Number (BBAN) that varies by country. Over 80 countries worldwide use IBAN, making international payments faster, cheaper, and more reliable.

IBAN validation uses the MOD 97-10 checksum algorithm. Here's how it works:

1. Rearrange: Move the first 4 characters (country code + check digits) to the end of the string.
2. Convert letters: Replace each letter with two digits (A=10, B=11, ..., Z=35).
3. Modulo 97: Treat the entire string as a large integer and compute number mod 97.
4. Check result: A valid IBAN always yields a remainder of 1.

This algorithm catches common transcription errors, single-digit mistakes, and digit transpositions with over 99% accuracy.

IBAN identifies a specific bank account (who you're paying), while SWIFT/BIC identifies a specific bank (where the payment goes). They serve complementary roles in international transfers:

• IBAN: Contains country, bank, and account details — used primarily in Europe, Middle East, and parts of Africa/Asia.
• SWIFT/BIC: An 8 or 11-character code identifying the bank and branch — used globally for routing messages between financial institutions.

For international payments within the SEPA zone, you typically only need the IBAN. For transfers outside SEPA, you may need both IBAN and SWIFT/BIC.

As of 2025, over 80 countries and territories have adopted the IBAN system. The IBAN length varies by country:

• Shortest IBANs: Norway (15 characters), Iceland (26 characters — but with a simpler BBAN structure)
• Longest IBANs: Malta and Seychelles (31 characters), San Marino (30 characters)
• Maximum possible: 34 characters (per ISO 13616 standard)
• Most common lengths: 20–27 characters

The length depends entirely on the domestic account numbering system of each country. Our tool supports all IBAN lengths from 5 to 34 characters.

Several reasons can cause a seemingly correct IBAN to fail validation:

• Check digit mismatch: The two digits after the country code are mathematically derived. A single typo anywhere in the IBAN will cause the check to fail.
• Wrong length: Each country has a fixed IBAN length. Even one extra or missing digit invalidates it.
• Invalid country code: The first two letters must be a valid ISO 3166-1 alpha-2 country code that participates in IBAN.
• Hidden characters: Copying from some sources may include invisible characters or non-standard spacing.
• Incorrect BBAN structure: Some validators also check that the BBAN follows the country-specific format rules.

Try removing all spaces and special characters, then re-enter the IBAN carefully.

You can typically find your IBAN in these places:

• Bank statement: Most banks print the IBAN on every statement.
• Online banking: Log into your bank's website or app; the IBAN is usually displayed under account details.
• Bank card: Some European debit/credit cards include the IBAN on the front or back.
• Bank branch: A teller can provide your IBAN upon request with proper identification.
• Welcome letter: The documents you received when opening your bank account.

Never share your IBAN on unsecured channels. While an IBAN alone cannot withdraw money, it should still be treated as sensitive financial information.

Yes! The check digits (positions 3-4) are calculated using the MOD 97-10 algorithm. To compute them:

1. Take the BBAN (without country code or check digits).
2. Append the country code (converted to numbers: A=10, B=11, etc.) and "00" (placeholder check digits).
3. Compute 98 - (number mod 97).
4. The result (padded to 2 digits) becomes the check digits.

For example, if the calculation yields 89, the check digits are "89". If the result is 1, the check digits are "01". Our tool performs this calculation automatically and can tell you what the correct check digits should be. Try entering an IBAN with modified check digits to see this feature in action!