The Strategic Power of Divisional Applications Before the EPO

Introduction

Navigating the patent prosecution process before the European Patent Office (EPO) requires not only a strong technical foundation but also a shrewd legal strategy. Among the most versatile and powerful tools at an applicant's disposal is the divisional patent application. While often viewed simply as a procedural remedy to administrative objections, the divisional application can be a cornerstone of comprehensive patent portfolio management in Europe.

Addressing Lack of Unity of Invention

At its most fundamental level, the divisional application serves as the primary mechanism for resolving a lack of unity of invention. Under Article 82 of the European Patent Convention (EPC), a European patent application must relate to one invention only, or to a group of inventions so linked as to form a single general inventive concept. When the EPO determines that an application claims multiple, distinct inventions, the applicant is forced to choose which single invention to pursue in the parent application. The term “parent application” refers to the immediate application on which the divisional application is based.

Without the ability to file a divisional, the non-elected inventions would be permanently lost. By filing a divisional application, the applicant can seek protection for these separate inventions into distinct applications, preserving the original filing and priority dates while ensuring that every valuable aspect of their technology is fully protected.

Accelerating the Grant of Allowable Claims

Beyond curing unity objections, divisional applications offer a relevant tactical advantage for expediting patent grants. It is common during prosecution that the Examining Division or the Opposition Division indicates that a specific subset of claims meets all patentability criteria, while objecting to other, often broader, claims in the same set. If an applicant chooses to argue the rejected claims, the entire application is delayed, keeping the otherwise allowable subject matter in a state of legal uncertainty.

To circumvent this bottleneck, applicants can strategically file a divisional application even when unity of invention is perfectly intact. By restricting the parent application exclusively to the allowable claims, the applicant can secure a rapid, enforceable European patent. Simultaneously, a divisional application can be filed to pursue broader or more contentious claims. This dual-track strategy ensures that the applicant immediately reaps the commercial and defensive benefits of a granted patent, while buying the necessary time and space to pursue with the EPO on the remaining subject matter.

No matter the abovementioned main objectives when filing a divisional application, the subject-matter of the divisional application must not extend beyond the contents of the parent application as filed. Therefore, amendments on the divisional application shall be restricted to the contents of the parent application as filed to meet the requirements of Article 123 (2) of the EPC.

Moreover, it is not mandatory to justify the legitimate need for division at filing or to explain the relationship between the divisional and the parent. When the applicant agrees with the objection regarding lack of unity raised or confirmed by the Examining Division, it is unnecessary that the applicant be required to explain the relationship between the claimed technical solution in the divisional claims and the parent claims.

Time limits to file a divisional application

A divisional application can be filed with the European Patent Office (EPO) while the parent application is pending.

There are several definitions for "pendency" according to the practice of the EPO, wherein each definition has a specific timeline for filing a divisional European patent application.

Start of pendency begins when a filing date has been awarded or when a PCT application enters the EPO Regional phase.

End of pendency is [1]:

ü  If a European patent is granted, until the day before the date of publication of the mention of grant;

ü  If a patent application is deemed withdrawn, until the last day of the unobserved time limit;

ü  If a patent application is actively withdrawn, until the day of receipt of the request for withdrawal;

ü  if a patent application is refused, without appeal, until the end of two-month period for filing a notice of appeal;

ü  if a patent application is refused, with appeal, until the termination of appeal proceedings.

Second generation divisional applications

The EPO allows that a divisional application be filed based on another divisional application (cascading divisionals). A divisional application (second-generation divisional application) can be filed based on another divisional application (first-generation divisional application) when the parent application has already been allowed with the proviso that, in the case of an application being filed as a divisional application from an application which is itself a divisional application, it is sufficient that the latter is still pending at the filing date of the second divisional application.

The flexibility provided by second-generation divisional applications is particularly useful considering that lack of unity of invention may be evident a priori, i.e., prior to carrying out a prior art search, or may become apparent a posteriori, i.e., after taking into account the prior art revealed by the search in terms of novelty and inventive step.

As an example, considering that an application as filed includes the subject-matter A, B and C, and that a priori, the EPO states in its European Search Report, that subject-matter A and subject-matter B and C do not share the same inventive concept, the applicant could file a divisional application including B and C and keeping only the invention A in the parent application.

In the sequence, if the EPO carries out the search for the unsearched matter B and C in the divisional application, and considers that B and C also do not meet the unity of invention requirement, the applicant can file a second-generation divisional application in order to obtain protection separately to B and C.

Double patenting and divisional applications

In general, for European patent applications from the same applicant with claims having the same priority date and relating to the same invention, the applicant must avoid claiming the same invention or choose one of the applications to proceed with. As acknowledged by the Enlarged Board of Appeal of the EPO, the prohibition on double patenting is applicable to under Article 125 of the EPC.

According to the approach of the EPO, an applicant can be allowed to proceed with an application that has the same description as a patent already been granted if it does not claim the same subject-matter.

Where two or more European patent applications from the same applicant designate the same state or states and their claims have the same filing or priority date and relate to the same invention, the applicant must amend one or more of the applications so that the subject-matter of their claims is no longer the same, withdrawn overlapping designations or choose which one of the applications is to proceed to grant.

The above-mentioned general guidelines are applied to a divisional patent application and the applicant must be cautious to avoid double patenting issues when filing a divisional application.

A European patent application is refused under the prohibition of double-patenting if it claims the same subject-matter as a European patent which has been granted to the same applicant and which does not form part of the state of the art under Articles 54(2) and (3) of the EPC for the European patent application under examination.

The applicant must bear in mind that two claims are not directed to the same subject-matter if they differ by at least one technical feature. If the claims of the European patent applications are merely partially overlapping, there is no impermissible double-patenting.

Disclaimers can be a useful approach to avoid double-patenting. EPO does not define criteria that allow for disclaimers not disclosed in the application as filed to solve issues regarding double-patenting. However, a disclaimer which is not disclosed in the application as filed may be allowable only for the following situations:

restoring novelty by delimiting a claim against a state of the art under Article 54(3) and (4) of the EPC;

• restoring novelty against an accidental anticipation under Article 54 (2) of the EPC.

On the other hand, double patenting is not considered when two applications with the same effective date are received from two different applicants and claim the same subject-matter, wherein each one must be allowed to proceed as though the other did not exist.

Conclusion

Ultimately, mastering the use of divisional applications before the EPO is not just about keeping an application alive. Divisional patent applications can contribute to maximizing the commercial value, enforceability, and scope of the patent portfolio of an applicant.

[1] References to the European Patent Convention, Jelle Hoekstra, Delta Patents, 2025

Author bio: Vítor Moreira is Patent Manager at Inventa and can contacted at vmoreira@inventa.com.