A letter warning someone that he or she is or may be infringing intellectual property rights. Such a letter should be carefully drafted and timed because of the risk of providing grounds for a declaratory judgment action, as well as the risk of a suit for wrongful threats. A typical patent warning letter will usually include a claim chart. It may also include a demand that the recipient “cease and desist” from infringing the sender’s intellectual property rights, in which case it is also called a “cease and desist letter” or a letter of protest.