By IBAN and BIC bank connections are unitarily indicated for SEPA-transactions
The unitary format offers a cross-border possibility to check accounting connections for formal correctness already at the capture. Thereby typing errors of all kinds are detected reliably.
IBAN and BIC must be applied in SEPA payment transactions
Hence the EPC(EuropeanPaymentsCouncil) imposed the usage of this account representation for all SEPA payment transactions on using of fundamental payment methods.
IBAN and BIC must not be "calculated" by oneself
Although offers appear in all kinds by now and existing accounting connections in the form account number / bank code must be transferred into the representation IBAN / BIC, the sole valid information concerning this are reserved for the bank in charge of the account and the account owner. On one hand the bank codes, used in the IBAN, differ partially, on the other hand not all BICs of a bank can be used for payment transactions.