Returned Material Authorization is a process where approval comes from the supplier for the customer to return the inventory for credit, replacement, or repair.
You should create a Sales Order in order to create a Return Material Authorization (RMA).
When you create an RMA, the system creates an authorization number for the supplier to track the return of the inventory. When you create an RMA, a purchase order can be created to receive the products. This will also create a sales order to ship substitute items. Alternatively, instead of shipping a replacement item, a Credit Order can be created. You can specify how the system should create Purchase Orders and Sales Orders by setting up the processing options of Sales Order entry (P4210) and Purchase Orders entry (P4310), and specifying those versions in the Return Material Authorization Defaults (P40052).