5.1. Introduction

This chapter primarily deals with double patenting arising from the filing of a divisional application, but also treats the matter as it may arise in other procedural situations.

In G 4/19 (OJ 2022, A24) the Enlarged Board of Appeal endorsed the narrow reading of the term "double patenting" given by the referring board (T 318/14 date: 2019-02-07, OJ 2020, A104, points 17 to 23 of the Reasons). Double patenting in this narrow sense may arise in situations in which two or more European patent applications with overlapping territorial scope, directed to the same subject-matter and having the same effective date are filed by the same applicant. Because such applications do not form part of the state of the art according to Art. 54(2) or (3) EPC, their prosecution could lead to the same applicant being granted two or more patents directed to the same subject-matter and having an identical or at least overlapping territorial scope. There are three situations in which such European patent applications could have the same effective date: (i) a European patent application is filed on the same date as another European patent application of the same applicant (parallel filings); (ii) a European patent application is filed as a European divisional application (Art. 76(1) EPC) in respect of an earlier European patent application (divisional application); (iii) a European patent application is filed claiming the priority (Art. 88 EPC) of an earlier European patent application (internal priority) or both claim priority from the same national application (see G 4/19, point 9 of the Reasons).

In view of divergent case law on the legal basis for the prohibition of double patenting and the doubts raised as to whether the EPC contained any provision at all which could serve as legal basis, in T 318/14 date: 2019-02-07 the board referred points of law regarding the legal basis for the prohibition of double patenting, and the corresponding conditions for a refusal on this basis, to the Enlarged Board of Appeal in accordance with Art. 112(1)(a) EPC.

In G 4/19 the Enlarged Board of Appeal decided that a European patent application can be refused under Art. 97(2) and 125 EPC if it claims the same subject-matter as a European patent which has been granted to the same applicant and does not form part of the state of the art pursuant to Art. 54(2) and (3) EPC. The Enlarged Board also held that the application can be refused on that legal basis, irrespective of whether it: a) was filed on the same date as; or b) is an earlier application or a divisional application (Art. 76(1) EPC) in respect of; or c) claims the same priority (Art. 88 EPC) as the European patent application leading to the European patent already granted (for details, see below chapter II.F.5.2).

The technical boards have several times considered the notion of the "same subject-matter". According to established case law, a mere (partial) overlap does not prejudice the grant of a patent (see T 587/98, OJ 2000, 497; T 877/06; T 1491/06; T 1391/07; T 2402/10; T 2461/10; T 1780/12; T 621/15, T 1252/16; different view in T 307/03). See in this chapter II.F.5.3. On the relevance of the scope of protection for the issue of double patenting, see e.g. T 1780/12 and T 2563/11.