If you add the custom business rule: <SINGLEUSEDISCOUNTSATCOST>TRUE</SINGLEUSEDISCOUNTSATCOST> then the answer is YES. When this rule exists the system will allow a single use discount code to reduce the subtotal of an order to zero. This rule works in conjunction with <SINGLEUSEDISCOUNTS>TRUE</SINGLEUSEDISCOUNTS>. For example, you sell a $40 off coupon for $20 (ala groupon). The consumer comes to your site and puts a $39 item in the shopping cart. This item may have $9 in shipping and $5 of tax along with it. The new business rule will reduce the sub total to 0 but will charge the consumer shipping only (no tax will be charged because they paid 0 for the item and thus there is no tax to report.
