Patent opposition in India can be done either before or after the patent is granted. A person can file pre-grant opposition after publication of the application in Indian Patent Journal till the grant of the patent. Any interested person can file post-grant opposition within twelve months from the date of publication of the patent grant in the Indian Patent Journal. The grounds of opposition for pre-grant and post-grant oppositions are provided under sections 25 (1) and 25 (2) respectively of the Indian Patent Act 1970.
The grounds for both pre-grant and post-grant oppositions are the same. There is nothing that prohibits a pre-grant opponent from subsequently filing a post-grant opposition. However, there are some procedural differences between the two types of opposition. In pre-grant opposition, any person can move the representation, whereas only an interested person can file a post-grant opposition. Hearing in front of authorities is not mandatory in a pre-grant opposition.