Canada, the Philippines, and the United States were among the only countries to use
first-to-invent systems, but each switched to first-to-file in 1989, 1998, and 2013 respectively. Invention in the U.S. is generally defined to comprise two steps: (1) conception of the invention and (2)
reduction to practice of the invention. When an inventor conceives of an invention and
diligently reduces the invention to practice (by filing a patent application, by making, testing, and improving prototypes, etc.), the inventor's date of invention will be the date of conception. Thus, provided an inventor is diligent in actually reducing an application to practice, he or she will be the first inventor and the inventor entitled to a patent, even if another files a patent application, constructively reducing the invention to practice, before the inventor. However, the first applicant to file has the
prima facie right to the grant of a patent. Under the first-to-invent system, when two people claim the same invention, the USPTO would conduct an
interference proceeding between them to review evidence of conception, reduction to practice, and diligence. Interference can be an expensive and time-consuming process. == Canada's change to first-to-file ==