By S&S Co. Advocates & Solicitors · Published 30 September 2026 · Informational content, not legal advice: see our disclaimer
Two Different Windows, Two Different Tools
Indian patent law gives third parties two genuinely distinct opportunities to challenge a patent application or granted patent: pre-grant opposition, available at any time after publication of the application but before the patent is actually granted, and post-grant opposition, available for a limited window after grant. These are not simply the same procedure at different points in time: they differ in who can file, the procedural mechanics, and the strategic considerations involved, and understanding the difference matters for anyone monitoring a competitor's patent filings or considering whether to challenge one.
Pre-Grant Opposition Under Section 25(1)
Pre-grant opposition, under Section 25(1) of the Patents Act, 1970, can be filed by 'any person': a deliberately broad standing requirement that does not require the opponent to demonstrate any personal interest or commercial stake in the outcome, unlike many other jurisdictions' opposition mechanisms. It can be filed any time after the patent application is published but before the patent is actually granted, on any of the specified statutory grounds (including lack of novelty, obviousness, insufficient disclosure, and several other grounds set out in the section). Because pre-grant opposition can be filed anonymously or through an unrelated party without revealing the true opponent's commercial identity or interest, it is sometimes used strategically by competitors who prefer not to be publicly identified as challenging a specific application.
Post-Grant Opposition Under Section 25(2)
Post-grant opposition, under Section 25(2), operates under a materially different framework: it can only be filed by a 'person interested', a narrower standing requirement generally understood to require some genuine commercial or business interest in the technology or the outcome, rather than being open to literally anyone, and only within one year from the date the patent is actually granted (specifically, from the date of publication of the grant), after which the opposition window under this provision closes permanently. Because post-grant opposition targets an already-granted patent, it is heard by an Opposition Board and decided by the Controller following a more elaborate, adversarial-style procedure compared to pre-grant opposition, including the possibility of oral hearings and more extensive evidence exchange.
Why the Distinction Matters Strategically
A party who becomes aware of a competitor's patent application early, during the pre-grant window, generally has a real strategic advantage in using pre-grant opposition, since success at that stage prevents the patent from being granted at all, avoiding the need to unwind an already-granted right later. A party who only becomes aware of a competitor's patent after it has already been granted (which happens often, since monitoring every relevant application as it publishes requires active, ongoing surveillance many companies don't maintain) still has the post-grant opposition window, but only for one year from grant: after which this specific route closes, and a challenger is left with revocation proceedings before the Intellectual Property Appellate framework or as a defence in subsequent infringement litigation, which are generally more expensive, slower routes than either opposition mechanism.
Grounds Common to Both Mechanisms
Both pre-grant and post-grant opposition share a largely overlapping set of statutory grounds under Section 25: lack of novelty (prior publication or prior public knowledge/use in India), obviousness over prior art, the invention falling within a category excluded from patentability under Section 3 (such as certain software-related or business-method claims, subject to India's specific exclusions), insufficient or unclear disclosure in the specification failing to enable a person skilled in the art to work the invention, and failure to disclose or correctly disclose information required under the Act, including foreign filing information. A well-prepared opposition, whether pre-grant or post-grant, generally succeeds or fails on the strength of the prior art and technical evidence actually marshalled in support of these grounds, not merely on asserting them in general terms.
Practical Guidance
Companies operating in a technology space with active patent activity should maintain ongoing monitoring of relevant published patent applications specifically so that pre-grant opposition, with its lower standing bar and earlier strategic window, remains available as an option rather than being missed. Where a competitor's patent has already been granted and is less than a year old, post-grant opposition should be evaluated promptly given the strict one-year deadline; once that window closes, the available challenge routes become materially more limited and costly.
Frequently Asked Questions
Who can file a pre-grant opposition against a patent application in India?
Under Section 25(1) of the Patents Act, 1970, 'any person' can file a pre-grant opposition: a deliberately broad standing requirement that does not require the opponent to show a personal or commercial interest in the outcome.
Who can file a post-grant opposition, and is the standing requirement different?
Under Section 25(2), only a 'person interested' can file a post-grant opposition: a narrower requirement generally understood to require some genuine commercial or business interest, unlike the open standing for pre-grant opposition.
What is the deadline for filing a post-grant opposition?
One year from the date of publication of the patent's grant, after which this specific opposition route closes permanently, leaving revocation proceedings or an infringement-defence challenge as the remaining, generally more expensive options.
When can a pre-grant opposition be filed?
At any time after the patent application is published but before the patent is actually granted: there is no fixed window comparable to the post-grant one-year deadline, only the grant itself as the cutoff.
What grounds can be raised in a patent opposition?
Largely overlapping grounds for both pre-grant and post-grant opposition, including lack of novelty, obviousness, exclusion from patentability under Section 3, insufficient disclosure, and failure to properly disclose required information including foreign filing details.
References & Further Reading
This guide provides a general overview of patent opposition mechanisms. Specific procedural timelines and evidentiary requirements should be confirmed against the current Patents Act, 1970 and Patent Rules in force.
- Patents Act, 1970, Section 25(1): pre-grant opposition, grounds and procedure.
- Patents Act, 1970, Section 25(2): post-grant opposition, standing, timeline and procedure before the Opposition Board.
- Patents Act, 1970, Section 3: inventions not patentable.