Spaces are optional — the validator handles them automatically. Example: GB29 NWBK 6016 1331 9268 19 (UK, valid).
Result
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What an IBAN contains
Every IBAN is structured the same way, regardless of country.
Country code
Two letters (e.g. GB, DE, FR) — always the first two characters.
Check digits
Two numbers validating the whole IBAN via the ISO 7064 MOD-97 algorithm.
BBAN
The Basic Bank Account Number — bank, branch and account identifiers in a country-specific format.
How the checksum works
The MOD-97 test catches 98% of typo errors.
- • Rearrange — move the first 4 characters (country + check digits) to the end.
- • Convert — turn letters into numbers (A=10 … Z=35).
- • Modulo — divide by 97; the remainder must be 1.
- • Limitation — this validates structure, not the actual bank account's existence.
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