When inventors visit our Saint Louis Public Library Patent and Trademark Resource Center, one of the first things they ask me is, "Do I need a provisional patent?" Of course, as a librarian, I kindly advise them that I am not an attorney and can not provide them any legal advice. However, I can provide them a paper brochure and web site link that the United States Patent and Trademark Office has created to help inventors solve that question.
Since June 8, 1995, the United States Patent and Trademark Office (USPTO) has offered inventors the option of filing a provisional application for a patent which was designed to provide a lower-cost first patent filing in the United States and to give U.S. applicants parity with foreign application under the GATT Uruguay Round Agreements.
According to the USPTO, "a provisional patent application for a patent is a U.S. national application for patent filed in the USPTO under 35 U.S.C. 111(b). It allows filing without a formal patent claim,
oath, or declaration, or any information disclosure (prior art) statement. It provides the means to establish an early effective filing date in a later filed non-provisional patent application files under 35 U.S.C. 111(a). It also allows the term "Patent Pending" to be applied in connection with the description of the invention."
So, do still come in to visit the PTRC to talk with the Patent and Trademark Resource Center librarian. However, just do not expect to walk out with their decision of what you should be doing - filing a patent or a provisional patent. That will always be your decision.