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.  To ensure that you receive proper credit in the shortest amount of time, please don't return your product without that information.  Please contact us here or in chat found at the bottom right-hand corner of our website Mon-Fri MST from 8am until 4pm.