There is this line of code in version 17.4 in function UpdateVATOnLines from the Sales Line table: and ((SalesHeader."Document Type" <> SalesHeader."Document Type"::Invoice) or ("Prepmt. Amt. Inv." = 0)) line location is 5435.

The code is preventing you from using an invoice discount, if you've used Get Shipments Lines and pulled shipments from orders with prepayments.
Category: Purchasing
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Ideas Administrator

Thank you for this suggestion! Currently this is not on our roadmap. We are tracking this idea and if it gathers more votes and comments we will consider it in the future.

Best regards,
Business Central Team