Patent opposition is the statutory mechanism for challenging a patent application or a granted patent before the Indian Patent Office. Under Indian law, the Patents Act, 1970 provides two distinct tracks — pre-grant opposition under Section 25(1), available to "any person" after publication but before grant, and post-grant opposition under Section 25(2), available to "any person interested" within one year of grant.
Legal definition
Section 25 of the Patents Act, 1970 establishes the opposition framework:
Section 25(1) — Pre-grant opposition: Where an application for a patent has been published but a patent has not been granted, any person may, in writing, represent by way of opposition to the Controller against the grant of patent on specified grounds.
Section 25(2) — Post-grant opposition: At any time after the grant of patent but before the expiry of a period of one year from the date of publication of grant of a patent, any person interested may give notice of opposition to the Controller.
The grounds for opposition (common to both tracks) include: (1) wrongful obtaining of the invention, (2) prior publication (anticipation), (3) prior claiming in India, (4) prior public knowledge or public use in India, (5) obviousness and lack of inventive step, (6) non-patentable subject matter under Section 3, (7) insufficient description in the specification, (8) failure to disclose information under Section 8, (9) non-compliance with the convention application timeline, and (10) non-disclosure of source or geographical origin of biological material.
A critical distinction exists in standing: pre-grant opposition can be filed by "any person" — no specific interest is required. Post-grant opposition can be filed only by a "person interested," meaning someone engaged in, or promoting, research in the same field, or a person who has a commercial or legal interest.
How courts have interpreted this term
Novartis AG v. Union of India [(2013) 6 SCC 1]
Although decided on appeal from the Madras High Court (not through the opposition mechanism), this case illustrates the substantive grounds that apply in opposition proceedings. The Supreme Court upheld the rejection of Novartis's patent application for the beta crystalline form of Imatinib Mesylate, applying Section 3(d) (non-patentable subject matter) and finding that the claimed form did not demonstrate enhanced efficacy over the prior art compound.
Ajanta Pharma v. Allergan Inc. [(2017) IPAB]
The Intellectual Property Appellate Board allowed the post-grant opposition and revoked Allergan's patent for a combination ophthalmic composition, finding that the invention was obvious over prior art. The Board held that a combination of known elements that produces a predictable result does not satisfy the inventive step requirement.
F. Hoffmann-La Roche v. Cipla Ltd. [(2012) Delhi HC]
The Court noted that pre-grant opposition filings had increased significantly in India, particularly for pharmaceutical patents. The Court observed that the dual opposition mechanism (pre-grant and post-grant) provides robust public interest safeguards in the patent system, allowing third parties to challenge weak patents before and after grant.
Why this matters
India's patent opposition system is one of the most accessible in the world. The pre-grant opposition mechanism, available to "any person" without demonstrating specific interest, allows public interest groups, generic pharmaceutical companies, and civil society organisations to challenge patent applications that they believe do not meet patentability standards. This has been extensively used in the pharmaceutical sector, where patent oppositions have prevented the grant of patents on known drug combinations, polymorphs, and formulations.
For generic pharmaceutical companies, pre-grant opposition is a strategic tool for clearing the path for generic entry. By opposing patents before they are granted, generics companies can avoid the need for costly infringement litigation later. Post-grant opposition provides a second opportunity to challenge the patent within one year of grant.
For patent holders, opposition proceedings are a significant business risk. In India, the pharmaceutical sector sees the highest volume of oppositions, with pre-grant oppositions filed on a substantial percentage of pharma patent applications. The opposition proceeding is quasi-judicial — both parties submit evidence, hearings are conducted, and the Controller issues a reasoned decision.
For IP practitioners, the choice between pre-grant and post-grant opposition involves strategic considerations. Pre-grant opposition is faster and cheaper, but the opponent has no formal party status and cannot appeal an adverse decision. Post-grant opposition involves a structured hearing before an Opposition Board and the opponent has formal party status with full appeal rights.
Related terms
Broader concepts:
Related concepts:
Frequently asked questions
Who can file a pre-grant opposition in India?
Under Section 25(1) of the Patents Act, "any person" can file a pre-grant opposition. No specific commercial or legal interest is required. This broad standing has been used by public health groups, generic manufacturers, and even individual researchers to challenge patent applications.
What is the deadline for post-grant opposition?
Post-grant opposition must be filed within one year from the date of publication of the grant of the patent. After this one-year window, the only mechanism to challenge the patent is a revocation petition before the High Court under Section 64 of the Patents Act.
What are the most common grounds for opposition?
The most frequently invoked grounds are prior publication (anticipation), lack of inventive step (obviousness), and non-patentable subject matter under Section 3 (particularly Section 3(d) for pharmaceutical patents). In pharmaceutical oppositions, Section 3(d) — which excludes new forms of known substances unless they demonstrate enhanced efficacy — is the most distinctive Indian ground.
This entry is part of the Veritect Indian Legal Glossary, a comprehensive reference of Indian legal terminology grounded in statutory text and judicial interpretation.
Last updated: 2026-03-27. Veritect provides this content for informational purposes and does not constitute legal advice.