idoc debmas: how to add IBAN to bank data

In a SAP ECC 6.0 system I am creating idocs of type DEBMAS06.

Along other segments I am filling segment E1KNBKM. In order to send the IBAN I fill the fields

E1KNBKM-IBAN

E1KNBKM-IBAN_BANKS and

E1KNBKM-IBAN_BANKL

but the IBAN data is not processed by the system.

I am getting no error message, the idoc is processed and all bank data except the IBAN data is processed.

I searched at SDN and Service Market Place but could not find any note regarding the creation of IBAN using an idoc. I also tried to debug the processing of the idoc in transaction BD87 but I could not find the code which populates the IBAN values.

Using LSMW we are able to create IBAN entries. They are visible in table TIBAN.