It is possible for a customer to have one (or more) remote shopping cart(s) per vendor and one local shopping cart that stores items customers add to their cart while shopping on www.amazon.com. When a customer decides to purchase the items in their remote shopping cart, the operations enable you to specify, using the MergeCart parameter, whether the items in the customer's remote cart are purchased separately or added to the local shopping cart. If MergeCart is False, the default value in the US locale, the locale and remote carts are not merged. Instead, the customer is sent directly to Amazon's Order Pipeline to purchase the items in their remote shopping cart (only), as shown in the following figure.

This page and the ones that precede it in the Order Pipeline are completed by the customer to actually place the order.

If MergeCart is True, the items in the remote shopping cart are added to the local shopping cart and customers are sent to that cart when they click Place your order, as shown in the following figure.

The MergeCart value is set in CartCreate and CartAdd and can be changed by CartModify. The MergeCart value is included in the PurchaseURL, which is returned by CartCreate. As long as the PurchaseURL is used to purchase the items in the shopping cart, the MergeCart value will be correct. For more information, see PurchaseURL.