Convergent invoicing and FKKBIX: Single Payment BIT not created

[SAPSupport]

In case a sales is registered (in Commerce Cloud in our case), the API will be called which will create a BIT with IT data.
In case a sales is registered which is paid immediately at the kiosk, the API will be called which will create a BIT with IT and PY data.
In case a customer is at the kiosk and wants to pay a receivable which already exists in the system, our expectation is that the API is called and created a BIT with only PY data.
When invoicing it would clear the open amount on the customer account.

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[SAPSupport · Accepted solution]

It is not possible to create standalone payment billable items (PY-BITs). It is not correct either.  We recommend to create an IT BIT with a negative amount. In billing, this will be posted as a credit note and can be used to offset existing receivables as part of account maintenance.