1.1. EPC provisions on priority

According to Art. 87(1) EPC, any person who has duly filed, in or for (a) any State party to the Paris Convention or (b) any Member of the WTO, an application for a patent, a utility model or a utility certificate, or his successor in title, shall enjoy, for the purpose of filing a European patent application in respect of the same invention, a right of priority during a period of twelve months from the date of filing of the first application.

Articles 87 to 89 EPC provide a complete, self-contained code of rules on claiming priority for the purpose of filing a European patent application (see J 15/80, OJ 1981, 213, confirmed in e.g. J 9/07, G 1/15, OJ 2017, A82, G 1/22 and G 2/22, OJ 2024, A50, point 25 of the Reasons). However, since the EPC – according to its preamble – constitutes a special agreement within the meaning of Art. 19 Paris Convention, it is clearly intended not to contravene the basic principles concerning priority laid down in the latter (see T 301/87, OJ 1990, 335; G 3/93, OJ 1995, 18, G 2/98, OJ 2001, 413 and G 1/22 and G 2/22, point 25 of the Reasons).

Article 87 EPC as well as Art. 88(2), (3) and (4) EPC pertain to the material conditions under which priority rights may be derived from an earlier application. Art. 88(1) EPC concerns the procedural requirements to be met by an applicant desiring to take advantage of the priority of an earlier application, namely the filing of a declaration of priority and other documents with the EPO. These procedural requirements are further specified in the Implementing Regulations (R. 52 to 54 EPC). Art. 89 EPC prescribes the effect of a priority right, i.e. that the priority date shall count as the date of filing of the European patent application for the purposes of the delimitation of the prior art under Art. 54(2) and (3) EPC. In other words, the priority right allows the exclusion of everything that has become prior art between the priority date and the filing date (often referred to as "intermediate prior art") for the assessment of patentability (G 1/22 and G 2/22, point 26 of the Reasons).

In G 1/22 and G 2/22 the Enlarged Board referred to the four requirements underlying Art. 87(1) EPC, which can be set out as the following questions: "who?", "where?", "what?" and "when?" (G 1/22 and G 2/22, points 58 and 91 of the Reasons, see also T 844/18 summarised in this chapter II.D.2.7.1). The question whether the applicant of the later application is entitled to claim the priority of the earlier application (the issue of “who”), in particular as a successor of the applicant of the priority application, is often referred to as "formal priority" or "formal validity of the priority". This question was addressed in G 1/22 and G 2/22 (see in this chapter II.D.2). The "same invention" criterion of Art. 87(1) EPC (the issue of “what”) is often referred to as "substantive priority" or "substantive validity of the priority" and was the subject of two referrals to the Enlarged Board: G 2/98, OJ 2001, 413 and G 1/15, OJ 2017, A82 (see in this chapter II.D.4). The other two requirements are covered in this chapter II.D.3 ("where"), II.D.1.2 and II.D.2.4.2 ("when").