When should I file my Provisional Application for Patent?
Important note: If you've already disclosed your invention to the public (such as by sale, offer for sale, use in public or written publication), a provisional application may still be filed to establish a filing date, but you have exactly one year FROM THAT INITIAL DISCLOSURE to file your non-provisional application--your disclosure starts the clock. In other words: a non-provisional patent application must be filed no later than one year after the public disclosure. Such disclosures include, but are not limited to: sales, offers for sale, written publication, disclosure to potential partners or finding source. Please contact the USPTO or an attorney if you're unsure whether or not you fall into this category.
Particularly under the recently-enacted America Invents Act, filing a provisional application for patent as soon as possible is best. As soon as you can describe your invention in terms that will be recognizable to an examiner who later reviews your corresponding non-provisional application and has to determine whether the invention contained in both applications is the same, file your provisional application for maximum protection. If you need to file later provisional applications to make adjustments that fit within the original filing, you can always do this and then combine all your provisional applications into a final, corresponding non-provisional application. You can't broaden the original invention in subsequent provisional applications, but you can clarify, explain, hone or narrow it. This gives you a lot of flexibility as to how to proceed while ensuring that you have the best protection possible while you're putting the finishing touches on your invention.