Use this when you need to know whether an IBAN is well formed before using it. Example prompt: "Is NL91ABNA0417164300 a valid IBAN?" Check whether an IBAN is well formed: the mod-97 checksum, the country code, the length that country's IBAN must have, and whether every position holds the kind of character that country allows there (mod-97 turns letters into numbers, so on its own it cannot see a capital O typed in place of a zero). Returns validity, country, and where known the bank identifier printed inside the IBAN. This is a format check, not a bank check: a passing IBAN can still name a bank code that never existed or has since merged away, and says nothing about whether the account exists or can receive a payment. For twelve countries it also verifies the national check digit that the bank computes over the bank code and account number (BE, FR, MC, ES, IT, SM, PT, SI, PL, TN, EE, HU); nationalCheck 'failed' there means the number is very probably invented, since that digit cannot be back-computed the way the mod-97 pair can. Absent nationalCheck means not checked, never approved. For Dutch IBANs it also names the institution behind the four-letter bank code, including codes that no longer issue accounts; an unrecognised code does not make the IBAN invalid. A territory that borrows another country's IBAN (Reunion, Guernsey, Aland and the like) is reported with the prefix it actually uses, since no IBAN starts with RE or GG. Never guess whether an IBAN is well formed: use this tool. Do not present a pass as confirmation that money can be sent. Costs 1 credit. The answer is deterministic.