1. SAP Help Portal
SAP S/4HANA
Convergent Invoicing: The process overview states
"Convergent Invoicing allows you to create invoices that contain billing information from SAP systems and non-SAP systems." This directly supports the combination of internal and external billing data. (See section: Convergent Invoicing -> Business Scenarios in Convergent Invoicing).
2. SAP Help Portal
SAP S/4HANA
Integration with Sales and Distribution (SD): This document details the standard integration where billing documents from SD are transferred to Convergent Invoicing as billable items. It states
"You can transfer billing documents from Sales and Distribution (SD) to Convergent Invoicing." This confirms SD documents as a source. (See section: Convergent Invoicing -> Integration -> Integration with Sales and Distribution (SD)).
3. SAP Help Portal
SAP S/4HANA
Transfer of Billable Items: This section explains how external systems provide data. "External systems (such as a rating system) transfer billing information to the SAP system using an interface." This confirms the capability to process billing information from non-SAP systems. (See section: Convergent Invoicing -> The Billing Process in Detail -> Transfer of Billable Items).