When to file a provisional patent? At this point I assume you have decided a provisional patent is the best option for you and now you are trying to figure out when to file your provisional patent (ie: next week, next month, next year, etc.).
It is extremely important that you file your provisional patent application at the perfect time. When is the perfect time? That depends on several factors, such as:
- Have you disclosed your idea publicly or if its still secret?
- Are you planning on disclosing your idea to investors or customers in the near future?
- Can you afford the thousands of dollars it will cost to file a non-provisional in 12 months?
- What is your short and long term business strategy?
It might be helpful to ask for some professional help here because you don't want to make a mistake that could cost you your patent rights. Most people don't realize but you can block yourself from getting a patent if you are not careful. Once you show your invention in public, write about it publicly, or offer it for sale you have started the clock and you only have 1 year to get your provisional patent filed in the United States (you may have already lost patent rights outside of the United States if you publicly disclosed your idea before you filed your patent).
In March of 2013 the United States moved to a "First to File" patent system. Since then, it is now very important to try and get your patent application filed as soon as possible. I usually tell people that if you think you know what your invention will look like and how it will work then you are ready to file your patent. You do not need to build a working prototype but you should be able to describe in detail and show (with figures) what pieces and components your invention will have. If you can do that, you are ready to file.
Suggested Next Reading: Introduction to Filing Provisional Patent Application