Diagnosis
You have tried to post an IS-U invoicing request without businesspartner items. This is not permitted.

Procedure
If you have only invoiced order items that are all cleared by a 100%discount, this results in a bill with a net value of zero. Thereceivable and the discount can now, for example, be assigned todifferent transactions in Contract Accounts Receivable and Payable usingthe account key (posting area 1200). This leads to two business partneritems.