I'm building an online shop using Magento framework which will provide part exchange sales. Customer will select a product from catalog and finally he will place an order. Shop manager will go thrugh the order details and contact the customer to complete the order. Customer will decide to give back his old product as part - exchange for the order. We need to inform customer on invoice that part exchange took place and his order was discounted by eg. USD 100.

Best way of doing this is product with custom and negative price, but this is not allowed in Magento.

Is there any other way to achieve that ?

2 Answers 2


You can create custom options on a product that allow negative prices, here you can define the amount that you discount for the products you exchange. The exchange amount can't be greater than the productprice, the item-price will then be 0.

  • Thankyou Vladimir for your answer. Part-exchange ammount could be different for same product but ordered by someone else. It is shops manager job to put specific ammount of PX for order and it has to be done after order was placed. I don't think its possible to make this happen with standard magento. What I'm also asking is the best practice of doin so? (eg. extension on admin panel providing form to add negative value to order total and displaying it on invoice? magento.ikantam.com/qa/how-add-discount-total-magento)
    – maquowicz
    Commented Jul 12, 2013 at 13:17

If shop admin will process each order manually then another approach could be issuing and applying a discount coupon for each order.

Options with negative prices can be not a good thing when it comes to ERP synchronisation.

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