When a learner selects a course/program to enroll in from a catalog, they should be presented with the option to have an invoice sent or the option to pay by credit card (payment gateway).
When a learner selects the invoice option rather than the option to pay by credit card, they should be allowed to select whether they will be paying by Check or Purchase Order.
Regardless of which option they choose (check or purchase order) there should be an optional field for the learn to enter a check number or purchase order number.
(The subcatalog administrator should be able to add information regarding where to send the check or purchase order.)
The learner should then be able to click a button to generate a printable invoice.
The subcatalog admin should be able to update whether a check/PO has been received.
In the reporting tool, the subcatalog admin should be able to run a report on learners with outstanding/unpaid invoices.