Securing Protection for Improvements: Understanding Patents of Addition in India

Inventors rarely stop improving their creations the moment a patent is granted. A drug formulation gets refined for better absorption. A mechanical component is redesigned for greater efficiency. A software process is optimized to reduce latency. When these improvements arrive after a patent application has already been filed – or after the patent has been granted – inventors face a practical dilemma: do they file an entirely new patent, or is there a simpler route? Indian patent law has a dedicated answer to this question: the patent of addition.

What is a patent of addition? 🔗

Under Section 2(1)(q) of the Patents Act, 1970, a “patent of addition” is formally defined as a patent granted in accordance with Section 54 of the Act. In plain terms, it is a separate patent that an inventor can obtain specifically for an improvement or modification of an invention already covered by an existing (or pending) patent – referred to as the main invention. The concept was introduced in Indian law based on the recommendations of the Justice N. Rajagopala Ayyangar Committee, which drew inspiration from Section 26 of the UK Patents Act, 1949, and has roots tracing back to the Indian Patents and Designs Act, 1911.

The key distinction of a patent of addition from a standard independent patent is that it exists in a dependent relationship with the main patent. It does not stand on its own in the same way a fresh patent does – its fate is tied, in significant ways, to the original patent it builds upon.

When can a patent of addition be filed? 🔗

Not every minor tweak to a product qualifies for a patent of addition. There are specific legal conditions that must be met before the Indian Patent Office will entertain such an application.

The improvement must relate to the main invention 🔗

The modification or improvement claimed must directly relate to the invention covered by the main patent or pending application. As clarified in case law, the proper comparison is between the novel contributions of each specification – the improvement must achieve the same result better, faster, or more cheaply, or achieve an altogether superior result. A mere “workshop improvement” – a trivial, routine adjustment any skilled person would make – does not qualify.

Same applicant or patentee 🔗

Only the applicant or patentee of the main invention can file for a patent of addition. A third party cannot separately claim a patent of addition over someone else’s invention. However, as Global Patent Filing notes, the inventors named in the patent of addition may differ from those in the main patent – provided the new inventors formally assign their rights to the same applicant or patentee.

Filing date requirement 🔗

Under Section 54(3) of the Patents Act, 1970, the filing date of the patent of addition application must be the same as or later than the filing date of the main invention’s application. A patent of addition cannot have a priority date that precedes the main patent’s filing date.

Main patent must be active 🔗

A patent of addition can only be filed against an active main patent application or a granted patent. If the main patent has lapsed or been abandoned, there is no basis for filing a patent of addition in relation to it.

Grant cannot precede the main patent 🔗

Section 54(4) makes it explicit: a patent of addition shall not be granted before the grant of the patent for the main invention. The Controller of Patents will not issue the patent of addition while the main patent application is still pending – it waits for the main patent to be granted first.

The inventive step question: a key advantage 🔗

One of the most practically significant features of the patent of addition mechanism is how it handles the question of inventive step. Under normal patent law, an invention must demonstrate a non-obvious inventive step over prior art. When the improvement is incremental – building closely on the main invention – it might struggle to clear that bar as an independent patent.

The Patents Act, 1970 specifically addresses this. Section 56(2) provides that the disclosure in the main application or patent shall be taken into account when determining the novelty of the patent of addition – but critically, an improvement or modification that lacks an inventive step over the main invention can still proceed to grant as a patent of addition, as long as the main patent itself is granted in India. This makes the patent of addition a cost-effective and strategic route to protect incremental innovations that might otherwise be rejected as obvious over the parent invention.

Converting an existing patent into a patent of addition 🔗

What if an inventor has already obtained two independent patents, and it later becomes clear that one is essentially an improvement over the other? Section 54(2) of the Act allows for this situation. Where a patentee holds two independent patents and one can be characterised as an improvement or modification of the other, the Controller may, on request, revoke the patent for the improvement and re-grant it as a patent of addition – bearing the same date as the revoked patent. This conversion is only possible if the filing date conditions under Section 54(3) are satisfied.

Term of a patent of addition 🔗

While a standard patent in India has a term of 20 years from the date of filing, the term of a patent of addition works differently. Under Section 55 of the Patents Act, 1970, the patent of addition runs concurrently with the main patent. It does not get its own fresh 20-year countdown – it expires when the main patent expires.

This means if a patentee files a patent of addition five years after the main patent was filed, the patent of addition will have, at most, 15 years of remaining life (assuming a 20-year main patent term). The two patents live and die together.

What happens if the main patent is revoked? 🔗

The situation changes if the main patent is revoked. In that event, the patentee may apply to the Controller to have the patent of addition converted into an independent patent. If the Controller grants this request, the patent of addition continues in force as an independent patent for the remainder of the original term – that is, the time that would have been left on the main patent had it not been revoked. This provides a meaningful safety net for inventors who have invested in building their patent portfolio around a main invention that is subsequently challenged successfully.

Renewal fees: a significant financial benefit 🔗

One of the most attractive features of a patent of addition is its renewal fee structure. Under the proviso to Section 55 of the Act, no renewal fees are payable for a patent of addition as long as it remains linked to the main patent. This is a direct financial saving – the patentee pays renewal fees only once (for the main patent) and the patent of addition rides along without additional annual charges.

However, this benefit ends if the patent of addition is converted into an independent patent following revocation of the main patent. From that point forward, the same renewal fees as those applicable to an independent patent become payable – calculated as if the patent had originally been granted as an independent patent.

Validity of a patent of addition 🔗

Section 56 of the Patents Act, 1970 deals with the validity of patents of addition. A notable protection provided here is that the validity of a patent of addition cannot be challenged solely on the ground that the invention claimed was obvious over the main invention. This is consistent with the relaxed inventive step standard discussed earlier and provides a layer of legal security for the patentee.

The grounds on which a patent of addition can be revoked include lack of inventive step in a broader sense, improper use of the main invention’s specification, or other standard grounds applicable to patents generally. However, being “too close” to the main invention is not, by itself, a ground for invalidation – which is precisely what makes the patent of addition route legally defensible.

Filing a patent of addition: procedural requirements 🔗

The application for a patent of addition is filed using Form-1 at the Indian Patent Office – the same common application form used for regular patent applications, which has a dedicated section for patents of addition. As per Rule 13(3) of the Indian Patent Rules, 2003, the complete specification accompanying the patent of addition must contain a specific reference to the main patent application and must include a definite statement explaining the improvements or modifications over the main invention.

A patent of addition can also be filed as an international application under the Patent Cooperation Treaty (PCT) designating India. Section 138(4) of the Patents Act confirms that such an international PCT application shall have the effect of a filing under Section 54, making the route accessible to inventors pursuing global patent protection simultaneously.

Why the patent of addition matters strategically 🔗

Beyond the legal technicalities, the patent of addition is a valuable tool for building a coherent patent portfolio. Research-intensive industries – pharmaceuticals, chemicals, engineering, electronics – frequently see inventions evolve incrementally over time. Each improvement, if left unprotected, can be freely exploited by competitors once the main patent expires. By filing patents of addition, inventors ensure their improvements are documented, protected, and legally enforceable during the life of the main patent.

It also serves as a mechanism to plug gaps in the original patent. No inventor can anticipate every application or variation of their invention at the time of the original filing. Patents of addition allow for these gaps to be covered retrospectively, without the full cost and complexity of an independent patent prosecution. At the same time, because the term of a patent of addition cannot exceed the main patent’s term, the law ensures this mechanism is not misused to artificially extend protection over the core invention – a safeguard against what is sometimes called “evergreening” in the pharmaceutical context.

What do you think? If an inventor improves their own patented drug formulation three years after the original patent is granted, should that improvement always be filed as a patent of addition rather than an independent patent – or are there situations where an independent filing would serve the inventor better? And given that a patent of addition’s life is capped by the main patent’s term, does this limitation fairly balance the interests of inventors and the public?

References

1. https://indiankanoon.org/doc/1937976/
2. https://www.lakshmisri.com/insights/articles/patent-of-addition/
3. https://www.globalpatentfiling.com/blog/patent-addition-india-approach-protect-improvements-invention
4. https://www.majumdarip.com/blog_post/patent-of-addition-a-strategy-for-incremental-innovation/
5. https://blog.ipleaders.in/comprehensive-overview-patent-addition/