Who's you? If you mean Amazon, then they know. Individual sellers don't know, correct. If you as a seller want to be able to get the same units shipped back, t

Who's you? If you mean Amazon, then they know. Individual sellers don't know, correct. If you as a seller want to be able to get the same units shipped back, then don't use the manufacturer barcode program. Barcodes matter so the warehouse can scan and know which product has been shipped in. Every product in the system requires a barcode of some sort.