When should I file for a patent?

If you have an idea that you view as worth protecting, you should file a patent application before you disclose the idea to any third parties.  In the United States, you have a 1 year grace period from the time you publicly use, disclose, or offer for sale your idea to file for a patent.  If you wait past that time, your idea is deemed to be in the public domain and you are barred from obtaining patent protection.  Many foreign countries do not offer any grace period and any public disclosure prevents you from obtaining a patent application.

The U.S. and most, if not all, foreign countries use a first to file patent system.  This means that the first person or company to file a patent applications gets the patent, regardless of who invented it first.  One exception is that if the inventor can prove that the earlier filer derived (or stole) the invention the subsequent filer is entitled to the patent.  The first to file system has placed an added importance on filing as soon as possible.

The purpose behind the patent system is that in exchange for you disclosing your idea to the public to further the arts and sciences, the law provides you with a 20 year pseudo-monopoly on your idea.  This gives you a 20 year exclusive right to sell your idea, use your idea, offer to sell your idea, to make your idea, and to import your idea.  After the 20 year period, your idea becomes a part of the public domain for anyone to use.  If your idea is already in the public domain, their is no incentive for the government to provide you with any exclusivity in the idea in exchange for your public disclosure of the idea.