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Patent criticality
The invention changed after you filed
We improved the product after filing. Is it still covered?
A patent application protects what it described on the day it was filed. Engineering does not stop on that day - and the version you eventually sell is often meaningfully different from the version you filed.
Why the gap opens
The filing captures the invention at a moment. Then testing changes a parameter, a supplier changes a material, a customer trial changes the architecture. Eighteen months later the product on sale uses a mechanism the specification never mentions.
The original application still covers what it described. It does not cover the improvement, and the improvement may not even be an infringement of your own claims - which means a competitor could conceivably patent it.
The three routes
A further application for the improvement, if it is independently new and inventive - noting that your own earlier application, once published, is prior art against it.
A patent of addition, where the improvement would be obvious over your own patent. It runs for the unexpired term of the main patent with no separate renewal fees, and the main patent cannot be used to attack its inventive step.
A divisional, if the improvement was actually disclosed in the parent but never claimed - which is why alternatives written into the original specification are so valuable.
All three have timing constraints. The point is to review, not to assume.
Sections 16, 54, 55 and 56 of the Patents Act 1970; amendment limits in sections 57 and 59.
Put a standing item on the engineering review: what has changed since we filed?
Assuming that improvements to a patented product are automatically inside the patent.
Any product change made between filing and launch.
Compare your current product specification with the patent specification you filed, feature by feature, and list what is not in both.
Sources & further reading
- The Patents Act, 1970 (consolidated to 1 August 2024) — Official IP India text
Related
Patent of addition
An application for an improvement or modification of an invention for which you already have a patent or a pending application, granted for the unexpired term of the…
Divisional application
A further application under section 16, filed in respect of an invention disclosed in the provisional or complete specification already filed, which may be filed at …
The divisional you could no longer file
A divisional application must be filed before the parent is granted. That is a moving target you do not control - and it is the single most common way that valuable …
What you can and cannot change after filing
After filing, you can narrow, correct and explain. You cannot add. Every amendment has to be supported by what was disclosed in the specification as filed - which is…
Not sure whether this applies to your invention?
The honest answer usually needs someone to look at your actual disclosure, your timeline and the prior art. That is a conversation, not an article.
Educational guidance, not legal advice. This material is published by Ragulika IP for general education and information. It is not legal advice, it does not create a professional-client relationship, and it is not a substitute for advice on your own facts. Patentability, infringement, prosecution strategy and every other IP outcome turn on the specific facts and on the law and Patent Office practice as they stand at the time you act. Please take professional advice before making a decision, and read the underlying provision or judgment before relying on any point stated here.
Last reviewed by Ragulika IP on 2026-08-23. Indian patent law and Patent Office practice change; check the position before you rely on it.