Divisional Applications and Double Patenting: When Portfolio Optionality Becomes Litigation Strategy

A divisional is worth what it allows its owner to argue later. G 1/25, and the referral now pending as G 1/26, sharpen a familiar point: that value comes from the choices made at filing and during prosecution, rather than from the number of applications kept alive.

The divisional application returns to the agenda this week, as the AIPPI World Congress in Hamburg, from 7 to 10 October 2026, takes up divisionals and double patenting. The debate is usually framed as a question of fairness to third parties: how long may an applicant keep subject matter pending, and how many patents may it obtain for the same invention? A litigator asks something else. Once proceedings have begun before the UPC, what does a family of divisionals actually allow the patentee to do, and what has it already lost through the way it prosecuted them?

The rules have not changed, but their consequences have

The legal frame is familiar. A divisional must be filed while the earlier European application is still pending, and it takes the earlier filing date, together with any applicable priority, provided its subject matter does not extend beyond the content of that application as filed.1 G 1/05 and G 1/06 settled the main structural questions: the divisional must satisfy Article 76(1), and the claimed subject matter of a later-generation divisional must be directly and unambiguously derivable from every preceding application as filed.2 A passage present in the first application but dropped from an intermediate divisional cannot be recovered further down the chain.

What has moved is the way claims are read, and with it the way the content of the earlier application is compared with what the divisional claims. In G 1/24, the Enlarged Board held that the description and drawings must always be consulted in interpreting the claims for the purposes of patentability under Articles 52 to 57 EPC, even where the wording seems clear read on its own.3 G 1/25 then held that the description must be adapted to amended claims only where an inconsistency created by the amendment would result in non-compliance with one of the provisions listed by the Board, Article 76(1) among them.4 Formal consistency alone is not enough: the inconsistency must carry a legal consequence. The Board added that problems of this kind under Articles 76(1), 83 and 123 were largely theoretical and would arise rarely, if at all.

The drafting lesson for divisionals is a narrow one. Copying the parent's description is not added matter in itself, and keeping an unclaimed embodiment is not objectionable on its own. What counts is the meaning the divisional's claims take in context, and whether the combination claimed was disclosed from the outset. The description cannot impose a restriction, or an extension, that the claim wording does not support. G 1/25 calls for a careful review of definitions and of inconsistent statements. It does not make every copied description suspect, and it does not cure a missing original disclosure.

The question G 1/26 leaves open

The referral in G 1/26 runs along the boundary between interpreting a claim and importing a feature from the description. In T 873/24, Board 3.3.05 asks, among other things, whether Article 123(2) requires every technically sensible reading of the claim wording to be tested, or only the readings established from the patent as a whole.5 The answer could matter for Article 76(1), which likewise requires a direct and unambiguous original disclosure. The point remains an implication to be drawn for divisionals, and the Enlarged Board has yet to rule on it.

In practice, the question is whether the description genuinely settles the meaning of the words used, or whether it supplies a missing limitation that rescues the claim. T 412/24 already shows the danger for divisionals: the Board refused to read a restriction from the description into a claim when assessing Article 76(1).6 Until G 1/26 is decided, prosecution should not be built on the assumption that an omitted feature can be restored by interpretation. The EPO has in the meantime directed examination and opposition proceedings to continue while the referral is pending.

Double patenting belongs to examination

The second strand of the debate is often overstated and deserves a sober statement. In G 4/19, the Enlarged Board held that a European patent application may be refused under Articles 97(2) and 125 EPC if it claims the same subject matter as a European patent already granted to the same applicant, where the earlier patent is not prior art under Article 54(2) or (3) EPC. The holding covers applications filed on the same day, the relationship between a parent and its divisional, and applications claiming the same priority.7 All of that concerns examination before grant. Double patenting is not a ground of opposition, and it does not appear among the grounds of revocation exhaustively listed in Article 138(1) EPC, to which the UPC Agreement refers for revocation actions and counterclaims.8

What counts is identity of subject matter. Partial overlap does not suffice, and a shared description does not prevent separate grants for different claimed subject matter.9 A divisional directed to a narrower combination may therefore carry real value, subject to the disclosure and patentability requirements, and provided that combination is not already claimed in the granted patent, including in a dependent claim. Cosmetic rewording of the same invention stands on quite different ground.

Before the UPC, duplication of the parent is not in itself a ground for revoking the divisional. The attack has to be attached to an available ground, lack of novelty or added matter for instance. Nor does G 4/19 settle every national question of concurrent protection: Article 139(3) EPC leaves simultaneous national and European protection to national law. Each situation turns on the procedural setting and on the rights being compared.

The family is not a single target

The order in Neurocrine Biosciences v. Spruce Biosciences shows the limits of a win against a single member of the family. On 13 March 2026, the Milan Central Division disposed of the revocation action concerning EP 3 784 233 after the patent had been definitively revoked at the EPO. Neurocrine had asked that disposal be made conditional on an undertaking by Spruce not to enforce any divisional against it. The Court held that this went beyond Rule 360: the action concerned the revoked patent and not other claim scopes, and the divisionals did not automatically share its fate.10 A defendant that prevails against one member of the family has prevailed against one patent. A patentee that loses one has lost one patent.

This is where the divisional takes on its real value as a litigation instrument. It allows a patentee to hold claims of different breadth, aimed at different products or different modes of use, each of which can be asserted, withdrawn or defended on its own record. For a defendant, the family becomes a moving target when a divisional is granted during the proceedings with claims directed to its product. That prospect does not dispense with the original disclosure requirement, and a newly granted patent does not enter the pending action by itself. Every asserted title calls for its own procedural and substantive analysis.

The consequence for settlement is just as concrete. Where commercial peace is meant to cover the family, the agreement has to say so, naming existing and future divisionals, the products concerned and the scope of any non-assertion undertaking. A dismissal concerning one patent does not deliver that bargain. The reverse holds as well: a defect in the common disclosure may bring down several members of the family, whose formal independence gives them no immunity from the same substantive objection.

What a patentee should decide at filing

The lesson of G 1/24 and G 1/25 is that the strength of a divisional in litigation is largely settled long before the action is filed, which condemns a few familiar habits. Copying the parent description as a reflex, without reviewing what it now implies for the divisional's claims, is one of them. So is filing divisionals whose claims differ from the parent in wording alone, where they add no distinct claim scope and expose the application to refusal for double patenting before the EPO. The costliest habit is to treat a pending divisional as a free option. Its value depends on the disclosure from which it was carved, and on the record the patentee builds while prosecuting it.

The better practice is to treat every divisional as a litigation asset in its own right from the day it is filed. The product or the conduct that the claims are meant to capture should be identified, each claimed combination mapped to the relevant passages of every preceding application as filed, the claims distinguished from those already granted in the family, and the description reviewed for inconsistencies carrying legal consequences. Kept up to date, that record shows what each divisional adds to the portfolio and which objections it remains exposed to. A patentee able to explain the architecture of its family to the judge rapporteur stands on firmer ground than one whose family looks like a stockpile.

For a defendant, the same analysis runs in reverse. The pending family deserves as much attention as the asserted patent, and an objection going to the original disclosure as a whole must be kept apart from one confined to a particular claim. The most useful question is usually whether this claim, read with this description, finds support in each relevant application as filed. A family may multiply the titles to be examined. It cannot multiply what was originally disclosed.

• 1Convention on the Grant of European Patents (EPC), Article 76(1); Implementing Regulations, Rule 36.
• 2EPO Enlarged Board of Appeal, G 1/05 and G 1/06, 28 June 2007, Orders.
• 3EPO Enlarged Board of Appeal, G 1/24, 18 June 2025, Order.
• 4EPO Enlarged Board of Appeal, G 1/25, 3 September 2026, reasons on claim interpretation and on Articles 76(1), 83 and 123 EPC, and Order. See M. Dhenne, G 1/25, Take Three: Anything You Leave in the Description May Be Used Against You, Kluwer Patent Blog, 10 September 2026.
• 5Technical Board of Appeal 3.3.05, T 873/24, 3 February 2026, published 3 June 2026; referral G 1/26 (Coated steel strips), questions 2 and 3. See also the EPO notice of 11 June 2026, OJ EPO 2026, A31, confirming the continuation of examination and opposition proceedings.
• 6Technical Board of Appeal 3.5.05, T 412/24 (Cloud-based analytics/Siemens), 25 July 2025, reasons 3.1.1.
• 7EPO Enlarged Board of Appeal, G 4/19, 22 June 2021, OJ EPO 2022, A24, Order and reasons 2–5.
• 8EPC, Article 100 and Article 138(1); UPCA, Article 65(2).
• 9EPO Guidelines for Examination, G-IV, 5.4, Double patenting.
• 10UPC Central Division, Milan Section, Neurocrine Biosciences v. Spruce Biosciences, 13 March 2026, UPC_CFI_722/2025, EP 3 784 233, paragraphs 20–23. The Dhenne Avocats case-law entry links to the official order.