Field help (BANKACCT) 

The value of this number defaults from the business partner profile and the address code. The bank account number format is dependent on the bank location.

For example, for an IBAN format, this field only contains the bank account number starting with the 5th character of the full IBAN.The prefix containing the country code and a control key is not included.

To change the bank account number, select the Business partner from the Actions icon available in the field to access the business partner profile, and select or enter a different bank account.