Packing slips and invoices are both pieces of paper or electronic documents associated with goods and services. While they are both important because of their role in accounting for where money goes and what a person or business receives in exchange for it, the former is sent to clients to bill them while the latter comes with goods to show the contents of a package.
Seller vs Shipper
A person or firm who sold the goods or service in question creates an invoice, which is essentially a bill for a customer. Either the seller or a third-party shipping service can create packing slips, on the other hand. Packing slips show the contents of a package rather than showing how much it costs and who must pay for it.
Invoices and packing slips have different purposes. An invoice is a billing document. It shows customers how much they owe, when they must pay it and what they purchased. A packing slip is a shipping document. It shows the receiver what should be in a package so he can ensure that everything arrived in one piece.
Packing slips are generally handled by the person who opens the container. This person varies depending on the size of a business and the package's destination; it could be an IT person, an accountant or a forklift driver, depending on the package and addressee. Invoices, on the other hand, are handled by accountants and accounts payable teams, as the former uses them to write off expenses and the latter must ensure they are paid.
Packing slips are not usually necessary after the delivery of a package. Once the recipient has confirmed the contents on the packing slip match the contents of the package, its work is done. Invoices, on the other hand, must usually be kept because they are used for taxes to write off expenses.