If a product is bought from the wholesaler by the case and sold from the shelf by the piece, the factor between the two units has to live somewhere. In TEON it is on the product card: the stock unit, the sales unit, the purchase unit and the unit of each barcode. For example, 1 case is 24 pieces.
On invoice, dispatch note and order lines the unit can be chosen, and a line opens with the unit set on the card. Scanning a case barcode puts 1 case on the line, with the equivalent in pieces underneath. The case price is the piece price times the factor; if you give a discount on the case, you change it on the line.
Stock always moves in the stock unit and cost is calculated per stock unit, so a product bought by the case and sold by the piece keeps a clean inventory. e-Invoices and e-dispatch notes carry the line’s own unit, with a “1 CASE = 24 PIECES” note on the line.