Value Changes from Cash Discounts 
Use
When creating a purchase order, the buyer can enter cash discount terms that have been agreed with the vendor. These cash discount terms appear as default values in Invoice Verification and can be changed if the terms have changed.
There are two ways to post cash discount amounts:
Gross Posting
In the case of gross posting, the cash discount amount is not taken into account at goods receipt or invoice receipt. The cash discount amount is not posted until the payment program is run, and then it is posted to a non-operating income account instead of to the stock account in question.
Net Posting
In the case of net posting, the cash discount amount is credited directly to the stock account. However, this procedure affects the stock account only if the material is valuated at a moving average price. If the material is valuated at a standard price, the cash discount is posted as a type of price variance. You can use net posting for goods receipts and in Invoice Verification. If you post the goods receipt net, it is best to post the invoice net; otherwise, the net posting at goods receipt would be canceled.
The document type determines which procedure is to be used:
For goods receipt, the document type is determined in Customizing. As a result, either all goods receipts are posted gross or all goods receipts are posted net.
In Invoice Verification, you can decide for each document whether you want to post the invoice gross or net. Note, however, that this choice only makes sense if the goods receipt was posted gross.
See also:
Gross Goods Receipt – Gross Invoice Receipt