What is the statute of limitations for invalid patent applications?

The limitation of action for invalidation of a patent application is two years, counting from the date when the patentee or interested party knows or should know about the infringement. If the patentee fails to pay the appropriate royalty before the patent right is granted after the publication of the application for a patent for invention, the limitation period for requesting the royalty is two years, counting from the date when the patentee knows or should know that others are using his invention. However, if the patentee knows or should know before the patent right is granted, it shall be counted from the date when the patent right is granted. Article 68 of the Patent Law of People's Republic of China (PRC)