Multi-fact reports include data from multiple data sources. They can contain a maximum of 3 data facts. When you create a multi-fact report, the main fact you select determines your choice of a second fact. Your choices for a third fact are then limited by your choices for the main and second facts.
Multi-fact reporting uses a set of pre-defined relationships to join data between facts along specific join fields. If two data values do not contain a join field, they cannot be used together in a multi-fact report. Including a join field in a report allows you to group and filter data more effectively. It also ensures that your report uses the lowest level of data.
For example, you can create a multi-fact report with the Purchase Order and Invoice facts. Both facts contain the field PO ID. The Join Fields Between Facts Example image shows how PO ID can act as a join field between the two facts to create a multi-fact report that shows PO Spend and Invoice Spend broken down by PO ID.

Note
Additional information about reporting facts and their associated join fields is available in these resources on the SAP Help Portal: