2.5.1 Introduction

A requirement for a valid priority claim is that the European patent application is filed by the applicant of the first application (i.e. the priority applicant) or by its successor in title. There are generally two factual situations before the boards involving a plurality of co-applicants for the priority application or the subsequent application or both. In the first, covered in this chapter II.D.2.5, an applicant is added in the subsequent application, i.e. the priority application is filed by one or more applicants and the subsequent application is filed by those applicants and one or more additional applicants (see e.g. T 1933/12, T 2719/19 date: 2023-11-20, T 2643/16 date: 2024-06-03). In the second, covered in this chapter II.D.2.6, not all applicants for the priority application are named in the subsequent application (see e.g. T 382/07, T 844/18, T 2360/19).