What happens after a provisional patent application expires?

A provisional application automatically becomes abandoned when its pendency period expires 12 months after the provisional application filing date by operation of law. Applicants must file a nonprovisional application claiming benefit of the earlier provisional application filing date in the USPTO before the provisional application pendency period expires in order to preserve any benefit from the provisional application filing (unless the benefit of the provisional application has been restored under 37 CFR 1.78).

Beware that an applicant who publicly discloses his or her invention (e.g., publishes, uses, sells, or otherwise makes available to the public) during the 12 month provisional application pendency period may lose more than the benefit of the provisional application filing date if the 12 month provisional application pendency period expires before a corresponding nonprovisional application is filed. Such an applicant may also lose the right to ever patent the invention.

Independent inventors should fully understand that a provisional application will not mature into a granted patent without further submissions by the inventor. Some invention promotion firms misuse the provisional application process leaving the inventor with no patent.

Source USPTO.GOV