Ideas are not patentable, inventions are. However, most clients I speak with that believe they only have an idea, actually have an invention. You do not need a working prototype to file a patent application. However, you must be able to provide “a written description of the invention, and of the manner and process of making and using it, in such full, clear, concise, and exact terms as to enable any person skilled in the art to which it pertains, or with which it is most nearly connected, to make and use the same, and shall set forth the best mode contemplated by the inventor of carrying out his invention.” 35 U.S.C. §112 In other words, you need to be able to describe your invention well enough that someone skilled in the relevant area of technology will understand the invention well enough to make and use it. If your idea is well enough developed to meet this requirement, you don’t just have an idea, you have an invention.