IBAN Validator

What is an IBAN?

An IBAN (International Bank Account Number) is an internationally standardized system for identifying bank accounts across national borders. Introduced under ISO 13616, IBANs were designed to reduce errors in cross-border transactions by providing a uniform account numbering format.

Before IBANs, each country had its own domestic account number format, leading to frequent mistakes when processing international wire transfers. The IBAN system solves this by embedding the domestic account details inside a structured envelope that includes built-in error detection.

How IBAN Validation Works

Every IBAN is validated using the MOD-97 algorithm (ISO 7064). The process works as follows:

1. Move the first four characters (country code + check digits) to the end of the string
2. Convert all letters to numbers (A=10, B=11, …, Z=35)
3. Compute the remainder of the resulting number divided by 97
4. If the remainder equals 1, the IBAN is valid

This algorithm catches over 99% of single-character errors and all transposition errors, making it extremely reliable for automated validation.

IBAN Structure

Every IBAN follows the same high-level structure:

Component	Length	Example (FR)	Description
Country code	2 letters	FR	ISO 3166-1 alpha-2 country code
Check digits	2 digits	76	MOD-97 checksum for error detection
BBAN	Variable	30006000011234567890189	Basic Bank Account Number (domestic format)

The BBAN (Basic Bank Account Number) varies by country. For France, it consists of:

• Bank code (5 digits)
• Branch code (5 digits)
• Account number (11 characters)
• National check digit (2 digits)

For Germany, the BBAN is simpler: a bank code (8 digits) followed by an account number (10 digits).

Country Lengths

Country	Code	IBAN Length
France	FR	27
Germany	DE	22
United Kingdom	GB	22
Spain	ES	24
Netherlands	NL	18
Belgium	BE	16
Norway	NO	15

Common Use Cases

• International wire transfers (SEPA): IBANs are mandatory for all SEPA payments within the European Economic Area
• Salary payments: Employers use IBANs to credit wages to employee bank accounts
• Direct debits: Utility companies and subscription services use IBANs for recurring payments
• Invoice payments: Businesses include their IBAN on invoices for smooth cross-border settlement
• Account verification: Financial platforms validate IBANs during onboarding to ensure correct bank details