We do not accept purchase orders but we do have an option that serves this function.
If you're an individual, when you are making your purchase in your shopping cart (after you have taken an online exam and passed), select the 'mail in a check' option from the drop down menu that gives visa/master card options. An invoice is created which you then can print and mail in with your check or money order.
If you are a company, after you have set up a company account -instructions here (https://goo.gl/7AHqsD), select the desired company plan to purchase. Next select 'mail in a check' from the drop down menu in your shopping cart that gives visa/master card options. An invoice will appear which you can print and mail in with your check or money order.