IBAN Validator
Check an IBAN against the ISO 13616 MOD 97-10 checksum
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MOD 97-10, in one paragraph
Move the first four characters to the end, replace every letter with two digits (A is 10 through to Z is 35), read the result as one long decimal number, and divide by 97. A valid IBAN leaves a remainder of exactly 1. The check is strong: it detects every single character error and effectively every transposition, which is why the standard has survived unchanged since 1997.
The resulting number can run to 38 digits, past what a double precision float can hold, so any implementation that parses an IBAN with a plain number type is silently wrong for long IBANs. This one folds the digits one at a time, which needs no big integer support at all.
Australia and New Zealand do not use IBAN
This is the question that brings most people here, so: there is no such thing as an Australian or New Zealand IBAN, and a bank in either country will not give you one. Australia uses a six digit BSB plus an account number, and New Zealand uses a sixteen digit bank-branch-account-suffix number. For international transfers into either country, what you need is a SWIFT/BIC code together with the local account details. You can check those with the BSB lookup and the New Zealand bank account validator.
A valid IBAN is not a real account
The checksum is arithmetic on the characters, so it says the number was typed correctly and nothing else. The account may never have existed, may be closed, or may belong to somebody other than who you were told. Many countries also carry a second, national check inside the account part, the French RIB key and the Italian CIN among them, which this tool does not verify. A bank can reject an IBAN that passes here, and that is not a contradiction.
Structure warnings
When the check digits are correct but the account part does not match the structure on file for that country, this tool says so as a warning rather than a rejection. The registry gains countries and occasionally revises entries, and refusing a real account number because our snapshot is a few months old would be the worse error. Sample values for every country in the registry are available from the IBAN generator.
Frequently Asked Questions
Does Australia or New Zealand have IBANs?
No. Neither country participates in the IBAN system, and no Australian or New Zealand bank will issue you one. Australia uses a six digit BSB plus an account number, and New Zealand uses a sixteen digit bank-branch-account-suffix number. For an inbound international transfer you supply a SWIFT/BIC code together with those local details.
How does the IBAN check work?
Move the first four characters to the end, replace each letter with a two digit value from 10 for A to 35 for Z, read the whole thing as one decimal number and divide by 97. A valid IBAN leaves a remainder of 1. The number can reach 38 digits, so implementations that use a normal floating point number get long IBANs wrong.
Why does my bank reject an IBAN that validates here?
The MOD 97-10 check only proves the characters are internally consistent. Many countries carry a second, national check inside the account portion, such as the French RIB key or the Italian CIN, and the bank code may simply not exist. A bank rejecting a structurally valid IBAN is normal and not a contradiction.
Are IBANs the same length in every country?
No, and assuming otherwise is one of the most common bugs in payment forms. Norway uses 15 characters, Germany 22, France 27, Malta 31. Each country also has its own account structure, which is why some IBANs contain letters in the middle and others are digits after the country code.