What item may or may not accompany a packing slip in a shipping carton?

An invoice is an important document that details the transaction between the seller and the buyer, including the items purchased, their quantities, prices, and payment terms. It typically outlines the financial aspects of a sale and serves as a formal request for payment. The invoice may or may not be included with the shipping carton, depending on the seller's shipping practices or the nature of the sale.

In many cases, businesses choose to send invoices separately from shipping cartons, especially for items that are shipped directly to the customer or when a packing slip suffices for the shipping process. This can help in maintaining confidentiality regarding pricing or serve to streamline the shipping process.

Other items, like a product catalog, shipping label, and delivery receipt, often accompany the packing slip for different purposes, such as promoting additional products, ensuring accurate delivery, or confirming that the package has been received. The invoice, however, is not always necessary to include in the same carton as the items being shipped, which is what makes it the correct choice in this question.