System should display a warning when users create a duplicate barcode for a different inventory item or unit of measure.
Copy/Paste use case: when you copy an inventory item, duplicate barcodes are automatically created. This leaves ambiguity when a barcode is scanned. System appears to use the oldest inventory item.
Data entry error use case: when entering inventory, users are allowed to enter duplicate barcodes. Users are not informed of the error so inventory discrepancies will occur and have to be resolved during cycle counting.
Same barcode for different items: it's possible that different vendors may use the same barcode for different products. This is not possible if you purchase from vendors who use standard industry codes such as UPC or GS1.