If you select the Manual check box in the Supplier discount codes (AP204000) window, the discount will not be applied automatically, or selected as the best-available when you save the document. You can use manual discounts for example for rebates or for coupons. Automatic discounts are applied when you save the document, but you apply a manual discount to documents in one of these windows:
You can apply manual line-level discounts to a document on the Document details tab in the correct window by selecting the discount code on a specific line. When you select the code and the system applies the discount, the other discounts are recalculated as well.
To apply manual group-level or document-level discounts, you select each manual discount by its code in the table on the Discount details tab in the correct window. If you change the line quantities while you are adding manual discounts, the system recalculates manual discounts; they will not be replaced by automatic discounts, even if the latter results in a bigger discount.
You can always go to the Discount details tab in the windows mentioned above, to view the details of the document-level and group-level discounts that were applied to a document.