Can I use the post office to protect my invention? The strategy is the inventor can write down their idea and mail it to themselves in a sealed envelope and use the postmark as proof that they invented on that date. This sounds like a cheap and easy way to protect an idea. This strategy does not work. There are two reasons why: one it does not matter who invented the first and two this is very poor evidence and would be torn to shreds in court if it were presented as proof. Why doesn’t it matter who is the first to invent? In 2013 new patent laws became effective that only grant patent rights to the first inventor to file a patent application. This was a major change in the law. You must be the first to file a patent application on an invention to be granted the patent rights. It does not matter if you were the first to invent. You must be the first file. I’ve talked to many inventors who have a great idea but do not act on it for years and by the time that they come talk to me someone else has already filed a patent application. With the first to file system it is more important than ever to keep your idea secret until you file a patent application. I have worked with inventors who have had their inventions stolen when somebody they showed the invention to filed their own patent application. I recommend documenting your invention and requiring signatures on a non-disclosure agreement from people that you show the invention to. Why would the post office patent be poor evidence? First you must think like a litigation lawyer. They will assume that you are lying. How do they know that you did not mail an unsealed envelope to yourself so you could use it later? All that the postmark really proves is that you paid for postage on a certain date. A much better way to document an invention is to keep an inventor’s notebook and have someone witness before a notary what you have invented. A notary may be about the same price as the cost of postage and gives you much better protection as proof in court that you invented the idea. Don’t rely on patent strategies that you hearing in rumors. Rely on advice from a professional.