An IBAN contains information that can be used to validate your account number, the country of origin of your bank, and other account details.
When you make a payment, the code is evaluated in the IBAN database to check that the payee is correct.
If an IBAN is entered into the database and there is no account associated with it, the transaction will fail. If a correlating account exists, the transfer will be finalized, and it can only be undone with the recipient's express permission.
Several banks, on the other hand, implement an IBAN checker, also called an IBAN lookup, to ensure that legitimate IBANs are error-free.