I think I may have submitted a request for this previously... if so feel free to use/reference my original request.
It's very time consuming (mostly for the customer) to process a return and then process a sale as different transactions. It would be so great if a return/exchange and a sale could be processes within the same transaction.
Yeah, I think you or another user had submitted this request. We basically just need to allow negative quantity at the iOS. We need to analyze the impact before making this change of course.