It should align with the Nature of return/Return reason, etc.. If you are planning to send the Items back to Customer (E.g. Rework return), you can return them as a Customer Owned stock. Otherwise, it should be a Company Owned stock.
For example, if it's a normal Sales part (E.g. a Faulty Laptop) delivered on a Company Owned Customer Order, then it should be returned and Handled as Company Owned stock. If you are returning an item expecting to send it back to Customer (E.g. returning a used Jet engine for an Overhaul), then it should be Customer Owned stock.