Invoices with discounts do not show in the payment selction until the actual discount date.
We have payment terms of 2%10 Net 45 setup and assigned to a supplier. An PO was issued and an invoice was matched to it. When we select payments the invoice does not show up in any payment selection list unless you run the Select Scheduled Payments with the exact date the First Discount (which is not always known)
We run payment batches weekly so an example would be that the first discount date was 03-JUL-2015 (Friday 10 days after the invoice was entered) and we run a payment batch on Thursday 02-JUL-2015 the invoice with the discount is not picked up in that payment run. The next payment run might be on Tuesday 07-JUL_2015 which is past the discount due date of 03-JUL-2015 so the discount is missed. I tested this and also ran a payment batch with 03-JUL-2015 date and the invoice shows up with the discount.