Below is the link from SAP help to explain the output control. It is using condition technique.
This link is a rough explanation for condition technique.
Use
You can make settings so that when you post an incoming invoice, the system displays invoice document numbers generated in Materials Management, and the document number of the accounting document in Financial Accounting, and also the number of the invoice reduction document.
This applies to the following transactions:
Activity
Activate display of the MM and FI document numbers using the user parameter IVFIDISPLAY, by entering the value X for the user. In the standard system, only the document number from Materials Management is displayed.