On the invoice that was in the box that your order came in, the SO number can be found near the upper right-hand part of the invoice.  If you have any questions, please don't hesitate to call us and we will assist you.  In order to ensure that you receive proper credit in the shortest amount of time, please don't return your product without that information.  Please call us at 1 (800) 233-6283, Mon-Fri, from 8am until 4pm MST or chat in Tues-Fri MST from 8am until 4pm.