I am using eBusiness Web Services to create a sales order. I create the SalesOrder in code and add a miscellaneous item SalesOrderLine with a negative extension amount to act as a discount on the order if someone is using a gift card as a payment.

Then when I use the PreviewSaleOrder() method to create the sales order to test the values, when I send the sales order in the extension amount is -5, but the sales order that is returned has an extension amount of 0.

Does anyone know why this would be happening?