We are using QM in sale for customer return SO. We activated inspection type 9902 customer return with Movement type 655.
We create return sale order and against return SO does the GRN at that time inspection lot generates for Inspection type 9902.material goes to quality stock.
After this quality department check whether this material is accepted or Rejected and provide usage decision.In case of rejected we provide Credit Invoice to customer against Return SO.
Now we want validate or control on Credit Invoice will be issue only In case of Usage decision is rejected (Material is block).
Similarly we use Invoice block functionality for Vendor through control key.