IBAN Validator

Validate IBAN numbers with mod-97 check and country format verification

What is it and how does it work?

An International Bank Account Number (IBAN) is a standardised format for identifying bank accounts internationally, established by the International Organisation for Standardisation (ISO 13616) and the European Committee for Banking Standards (ECBS). An IBAN consists of: a 2-letter country code, a 2-digit check number, and a country-specific Basic Bank Account Number (BBAN). A German IBAN looks like DE89 3704 0044 0532 0130 00 (22 characters); a UK IBAN is GB29 NWBK 6016 1331 9268 19 (22 characters); they vary from 15 (Norway) to 34 characters.

IBAN validation uses the MOD 97 algorithm: move the 4 leading characters to the end, replace letters with numbers (A=10, B=11, ..., Z=35), interpret the result as a large integer, and verify that number modulo 97 equals 1. This provides a mathematical guarantee against transposition errors — swapping two adjacent digits will almost always produce an invalid IBAN. This tool validates the check digit and structure without making any network request.

Common use cases

• Wire transfer verification: before submitting an international wire, validate the recipient's IBAN to catch typos that could send funds to the wrong account or cause an expensive manual investigation fee.
• Payment form validation: validate IBAN in a payment form before submission — the MOD 97 check catches ~99% of single-character errors, preventing failed transactions.
• Data quality: clean a spreadsheet of IBANs by validating each one and flagging any that fail the check digit — common after manual data entry or CSV import with formatting errors.

Frequently asked questions

How does the MOD 97 IBAN validation algorithm work?

Step 1: Move the first 4 characters (country code + check digits) to the end. Step 2: Replace each letter with its numeric equivalent (A=10, Z=35). Step 3: Interpret the entire string as a number. Step 4: Compute number mod 97. If the result is 1, the IBAN is valid. Example: DE89370400440532013000 → 370400440532013000DE89 → 3704004405320130002314 89 → mod 97 = 1 ✓

What is the difference between IBAN and SWIFT/BIC?

IBAN identifies a specific bank account. SWIFT/BIC (Bank Identifier Code) identifies a specific bank or bank branch. For an international transfer, you typically need both: the IBAN of the recipient's account and the BIC of the recipient's bank. In SEPA (Single Euro Payments Area) transfers, only the IBAN is required — the bank can be inferred from the IBAN.

Which countries use IBAN?

IBAN is mandatory in SEPA countries (all EU member states, UK, Norway, Switzerland, Iceland, Liechtenstein) for euro transfers. It's also used in many Middle Eastern and North African countries (Egypt, Jordan, Saudi Arabia, UAE), some Latin American countries, and others. The US, Canada, Australia, Japan, and China do NOT use IBAN — they have their own account number systems (ABA routing numbers, BSB, etc.).

Can an IBAN fail validation but still be a real account?

If an IBAN fails MOD 97 validation, it definitely has an error — no legitimate IBAN can fail this check. However, an IBAN that passes validation is not necessarily a real account: it could be a correctly formatted but non-existent account number. Validation proves structural correctness; only the receiving bank can confirm the account exists.

Utility

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