An IBAN's validity check is entirely structural: the country code maps to a fixed-length national bank account format, and the two check digits satisfy the ISO 7064 MOD-97-10 checksum. That is the limit of what a checksum can tell you. It says nothing about whether the account exists, is open, or belongs to a real bank.

This generates IBANs that pass that structural check for any supported country, and validates the checksum on any IBAN you already have.

When you'd use this

QA and staging environments that need realistic-looking bank account data without using a real one, or risking exposing it: payment form testing, database seeding, load testing an onboarding flow.

Validating an IBAN a customer or partner sent you, when you just need to catch an obvious typo (wrong length, transposed digits) before it reaches a real payment processor.

Common errors

A length mismatch means the country code was recognized but the total IBAN length doesn't match that country's fixed format. Every IBAN country has one specific length, unlike some other identifiers where length can vary.

A checksum failure with a recognized country and correct length almost always means a single mistyped or transposed character somewhere in the account number portion.

Frequently asked questions