Thanks! Most of our orders are with a credit card, but occasionally by Purchase Order. With Wordpress we were able to accept PO as a method of payment but not with Squarespace. If a form option would be available maybe that would work?
It seems I am not the only one with the PO payment problem occasionally, from what I can see there is no way to work around this. We will just have our customers fax or email a PO if it comes up. But more an more a PO is not used so much by schools anymore.