IBAN Validation: Complete Developer Guide (2026)

If your app handles international payments, money transfers, or banking integrations, you'll need to validate IBANs. The International Bank Account Number is used across 80+ countries to identify bank accounts for cross-border transfers. Getting IBAN validation wrong means failed transfers, returned payments, and unhappy users. This guide shows you exactly how the validation works, with code you can drop into any project. What's Inside an IBAN? Every IBAN follows the same structure: DE 89 3704 0044 0532 0130 00 ── ── ───────── ───────────── │ │ │ │ │ │ │ └── Account number │ │ └── Bank code (BLZ) │ └── Check digits (MOD-97) └── Country code (ISO 3166-1) Country code (2 letters) — DE = Germany, GB = UK, FR = France Check digits (2 digits) — computed using MOD-97 to catch typos BBAN (Basic Bank Account Number) — the rest, format varies by country The total length depends on the country. Germany is 22 characters, the UK is 22, France is 27, and Norway is just 15. IBAN Lengths by Country C