Customer Purchase order number for recurring invoice

SUGGESTED

Can someone please tell me if the ONLY place for a recurring AR invoice purchase order number is in the actual line item description? I received a purchase order from a customer and they will be on recurring invoice, but I do not see where you can add a purchase order in the recurring invoice entry screen. Nor do I see it on the copy recurring invoice screens, but I do see that I can Modify Invoice Terms/ Header and add a PO#, but this is AFTER the invoice has been printed or emailed. How can I use the system to work WITH me in a efficient manner, rather than make me do extra steps for a normally standard thing as a customer PO number?

All advice is appreciated. Thanks.