Imported purchase invoices with vendor discounts

We need to import our vendor invoices via a .csv file. We have created the template and have successfully imported invoices into SAGE50. 

Problem: We have terms discounts on our vendors; these discount amounts show when we pay those vendors in the Payments function. That discount is not showing for our imported vendor invoices. We are including the following fields in our tempate:

Vendor ID Date Date Due Invoice/CM # Accounts Payable Account Ship Via Number of Distributions Serial Number G/L Account Amount Credit Memo Discount Amount

We added the "discount amount" field to see if it would fix the problem, but it didn't. It appears that the SAGE vendor discounts process needs to be triggered to populate the discount field on the payments screen. How to make that happen?