bank-lint

Validate bank and account details offline — no API calls, no dependencies.

v0.1 supports IBAN (ISO 7064 mod-97 checksum + per-country length across 89 countries). US routing numbers and UK sort codes are coming in later releases.

Part of a dual-language project: the same validation logic, verified against the same test vectors, is also available for JavaScript/TypeScript as bank-lint on npm.

Install

pip install bank-lint

Usage

from bank_lint import validate_iban

validate_iban("GB82 WEST 1234 5698 7654 32")
# ValidationResult(valid=True, value='GB82WEST12345698765432', error=None)

validate_iban("GB82 WEST 1234 5698 7654 33")
# ValidationResult(valid=False, value='GB82WEST12345698765433', error='INVALID_CHECKSUM')

Spaces and lower-case are handled for you; value is the normalised input.

API

validate_iban(value: str) -> ValidationResult

ValidationResult is a frozen dataclass:

valid: bool
value: str                    # normalised (spaces removed, upper-cased)
error: str | None             # None when valid

error is one of:

• "INVALID_FORMAT" — doesn't match the IBAN pattern
• "INVALID_LENGTH" — wrong length for that country
• "INVALID_CHECKSUM" — fails the mod-97 check
• "UNSUPPORTED_COUNTRY" — country code not in the registry

Scope

bank-lint checks the structural validity of a bank identifier — format, length, and checksum. It does not:

• confirm the account actually exists or is open,
• do name matching or Confirmation of Payee,
• look up bank or branch details.

Country IBAN lengths are sourced from the official SWIFT IBAN Registry.

License

MIT