When you make an international transaction, your bank's payments system runs the characters that make up your IBAN. The system can confirm the sender's and recipient's accounts by checking the numbers and letters against their records.
The account information is analyzed and checked using special procedures. The payment will be processed if it is valid.
If an IBAN is entered incorrectly and there is no account corresponding with that IBAN, the transaction will fail. If a corresponding account exists, the transfer will go through and can only be reversed with the recipient's permission.
But you don’t have to be worried as most banks use an IBAN checker to ensure that valid IBANs are free of errors.