Sellers offer postage discounts to encourage buyers to add more items to their carts.  A seller can apply the discount to the postage amount when the buyer buys more than one item. Besides postage discounts, sellers can also offer carrier-specific discounts or provide savings on postage as a promotional tool in the listings. For the postage discount to work, a seller has to offer combined postage. Once the combined postage option is set up, the seller can use rules that are applied automatically to the delivery amount when a buyer purchases multiple products.  On checkout, the discounts will be automatically applied rather than the seller having to create a revised invoice once the sale is completed. Based on whether a seller offers a flat postage cost or a calculated cost, the discounts can vary slightly.