Complementary sales refer to the practice of offering additional products or services that complement and enhance the value of a primary purchase. These additional items are not essential to the main purchase, but they add value and convenience for the customer. Complementary sales are often used as a strategic marketing technique to increase customer satisfaction and loyalty, as well as to boost overall sales and revenue. This can include offering related products, upgrades, or add-ons that enhance the original purchase, creating a more comprehensive and satisfying experience for the customer. In essence, complementary sales aim to provide customers with a complete and well-rounded solution, rather than just a single product or service.