You have several options for responding to a demand letter:
-You may respond by requesting more specific evidence as to why the patent owner believes you are using patented technology without a license. Note that the sender of the letter is not legally obligated to respond to your request, or to respond adequately, but even a non-response may be valuable in helping you to determine your next steps. If you have a basis for doing so, you may also respond to the letter and deny infringement. -You may elect to not respond to the letter or any follow-up letters. Some patent demand letters are sent in the hope that some recipients will be misled or intimidated into paying for licenses even though they do not need to do so. Those who believe that the claims contained in a letter are without merit have in many cases selected not responding to it as their best course of action. Doing nothing carries some risk, however, because if you are later found liable for infringement, the court may determine that you acted recklessly and subject you to up to three times the monetary damages. -You may negotiate with the patent owner for a license to use the patent on mutually agreeable terms, or to obtain an agreement that you do not infringe the patent. -You may want to explore suing the patent owner for a declaratory judgment stating that you do not infringe the patent claims, or that one or more of the patent claims are invalid.
An attorney can help you decide between these options and how to execute on them.