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IBAN

IBAN (International Bank Account Number) checksum using modulo-97 algorithm per ISO 13616. Validates international bank accounts with 2-digit check digits. Format: CC12BANK-ACCOUNT where CC is country code, 12 is check digits. Used in SEPA transactions worldwide.

Properties

Property	Value
Category	Checksums
Sub-category	Banking Standard
Security status	🎓 Educational Only
Complexity	Intermediate
Inventor	European Committee for Banking Standards
Year	1997
Origin	Not specified
Source	`algorithms/checksum/iban-checksum.js`

Security

Status: 🎓 Educational Only

No vulnerabilities are recorded for this implementation.

Notes

Format: CC12BBBBSSSSAAAA… (Country, Check, Bank, Branch, Account)
Algorithm: Move first 4 chars to end, replace letters with numbers (A=10…Z=35)
Calculate: mod 97 of resulting number should equal 1 for valid IBAN
Check digit calculation: 98 - (mod 97 of account with check=00)
Length varies by country: 15-34 characters
Detects: 97.3% of all errors
Detects: All single character errors
Detects: All double transposition errors
Used in: SEPA payments, international transfers

Documentation

References

python-stdnum IBAN implementation

Test vectors

3 vectors ship with this algorithm and run in the test suite. Byte values are hexadecimal.

Vector 1 — German IBAN

Field	Value
`input`	`44453839333730343030343430353332303133303030`
`expected`	`0001`

Vector 2 — UK IBAN

Source: IBAN validation

Field	Value
`input`	`47423832574553543132333435363938373635343332`
`expected`	`0001`

Vector 3 — Check digit calculation - Invalid IBAN

Field	Value
`input`	`47423030574553543132333435363938373635343332`
`expected`	`0010`

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