What is the legal effect of a patent being declared invalid?

Legal analysis: invalid patent right is considered to be nonexistent from the beginning. The decision to declare the patent right invalid has no retrospective effect on the patent infringement judgments and conciliation statements made and executed by the people's court before the patent right was declared invalid, the decisions on handling patent infringement disputes that have been performed or executed, and the patent licensing contracts and patent transfer contracts that have been performed. However, if the patentee's malice causes losses to others, it shall make compensation.

Legal basis: The patent right declared invalid in Article 47 of the Patent Law of People's Republic of China (PRC) is regarded as nonexistent from the beginning. The decision to declare the patent right invalid has no retrospective effect on the judgments and rulings of patent infringement made and executed by the people's court before the patent right is declared invalid, the decisions on handling patent infringement disputes that have been performed or executed, and the patent licensing and patent transfer contracts that have been performed. However, if the patentee's malice causes losses to others, it shall make compensation. In accordance with the provisions of the preceding paragraph, if the patentee or the patentee's transferor fails to return the patent royalty or patent transfer fee to the licensee or the patentee, which obviously violates the principle of fairness, the patentee or the patentee's transferor shall return all or part of the patent royalty or patent transfer fee to the licensee or the patentee's transferee.