When Purchase Order is selected as a payment option along with other options (I was using PO, telephone, COD) and the customer goes to checkout the form shows the option as Purchase order but also additional fields for credit card info, i.e., expiration date and csv code. To get the Purchase Order entry form to appear properly a different option must be selected from the drop down. Then if the PO is selected again the proper form appears with only the PO # entry field displayed. See attached image.