When working in WebPurchasing, it's possible to add a specific product to the cart for a requisition, or a user can create a one-time product. When creating and using a one-time product, it's possible to enter external notes on the requisition's one-time product line item. Once the requisition has been turned into a Purchase Order though, the external notes do not show on the miscellaneous P.O. line item the same way they do on a regular P.O. line item.
One-time products do not display external notes.
Alternative Solution: Create a new comment line item with the same information that was in the external notes. This will show in the body of the printed P.O.
Enter the external notes on the first tab of the P.O. at the bottom in the comments box there. These will be displayed at the bottom of the printed P.O. page.