Under Art. 82 EPC, the 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. R. 44(1) EPC (cf. R. 30 EPC 1973) gives an interpretation of the concept of unity of invention where a group of inventions is claimed. The principles set out by board of appeal case law relating to the earlier version of R. 30 EPC 1973 in force until 31.5.1991 can still be applied.
For international applications the corresponding provisions on unity of invention are Art. 3(4)(iii) PCT and in particular R. 13 PCT. Protests in respect of additional fees paid following a non-unity objection by the EPO acting as ISA (Art. 17(3)(a), R. 40 PCT) or as IPEA (Art. 34(3)(a), R. 68 PCT), which were previously decided on by the boards of appeal (Art. 154(3) and 155(3) EPC 1973), are now decided on by review panels of the EPO (R. 158(3) EPC, Decision of the President of the EPO, OJ 2015, A59; for the interim procedure applied between the entry into force of amended R. 40 and 68 PCT on 1.4.2005 and of the EPC 2000 on 13.12.2007, see Notice of 1 March 2005, OJ 2005, 226, and the "Case Law of the Boards of Appeal", 6th edition 2010, IX.A.1). The boards' competence to consider unity in the context of European applications remains unaffected. Given the harmonisation of the definitions concerning unity of invention in R. 13 PCT and Art. 82, R. 44 EPC, the criteria for unity in both systems are the same. Therefore, decisions of the boards of appeal rendered according to the former PCT protest procedures continue to be of interest for the consideration of unity in European applications.
The Guidelines for Examination in the EPO (November 2018 version) deal with unity of invention at the search stage in Part B‑VII, unity as a procedural aspect of substantive examination in Part C‑III, 3, and unity as a requirement of the European patent application in (extensively revised) Part F‑V. For international applications see especially Chapter GL/ISPE 10 of the PCT International Search and Preliminary Examination Guidelines, as in force from 1.1.2019, and the Guidelines for Search and Examination in the EPO as a PCT Authority, B‑VII, C‑V and F‑V – November 2018 version.