After a patent has been granted, within one year of the publication of the grant of the patent, any person interested can file post-grant-opposition against the grant of the patent. Post Grant opposition can be filed on the grounds mentioned in section 25(2). After the controller receives a notice of post-grant opposition, he informs the patentee. A copy of the statement and evidence shall be delivered to the patentee by an opponent. The patentee within two months of the receipt of the opponent’s statement and evidence can file a reply along with the evidence supporting his invention. If the patentee does not want to contest the opposition and does not file a reply within two months, then the patent is considered to be revoked. If a reply has been filed by a patentee then, within one month of filing a reply by the patentee the opponent can file his reply and evidence. No further reply will be submitted by either party, except in the direction of the controller.
An opposition board is constituted by the controller on receiving the notice of opposition. An opposition board consists of 3 members. One of the members is the chairman, second may be an examiner but not the same examiner who has dealt with the application.