In dealings between buyers and sellers, a tying arrangement is one in which the seller sells a product to a buyer on the condition that the buyer also buys an unrelated product from the seller. The unrelated product is sometimes called the "tied" product.
Sometimes, a tying arrangement requires the buyer to not buy a product from any other vendor.
Tying arrangements are generally viewed as problematic by the courts because of the way they seem to force buyers into unfairly being required to buy the tying product as part of what would otherwise be a valid contract. In fact, over the years, tying arrangements have often been prosecuted under antitrust laws. The rationale for these prosecutions is that a tying arrangement is used to entrench a seller’s market share and to restrict competition from sellers with better products.