b) Amendments intended to remedy a lack of clarity 

Objections to the clarity of claims or any consequent requests for amendment are only relevant to opposition proceedings in so far as they can influence the decisions on issues under Art. 100 EPC or arise in relation to the subject-matter to be amended as a consequence of such issues (T 127/85, OJ 1989, 271).

According to the established case law of the boards of appeal, Art. 84 EPC is an EPC requirement that has to be taken into account in opposition proceedings whenever the patent proprietor files any amendments (within the limits set in G 3/14, OJ 2015, A102; see in this chapter IV.C.5.2.2). However, Art. 84 EPC is not itself a ground for opposition under Art. 100 EPC. Irrespective of how the granted claims are formulated, and be they dependent or independent, an opposition cannot be lodged on the basis that they lack clarity (T 23/86, OJ 1987, 316; T 565/89; T 89/89; T 16/87, OJ 1992, 212; T 1835/08; T 1855/07). The board in T 89/89 followed the findings in decision T 295/87 (OJ 1990, 470) according to which amendments during opposition proceedings should only be considered as appropriate and necessary in the sense of R. 57(1) and 58(2) EPC 1973 and therefore admissible if they can fairly be said to arise out of the grounds of opposition (confirmed in T 792/95; now "occasioned by a ground for opposition" is a requirement under R. 80 EPC).

In T 2122/17 the board agreed with the parties that a lack of clarity under Art. 84 EPC arose from granted claim 8 because it contained an option that conflicted with a feature in granted claim 1. However, it considered that granted claim 8 also fell foul of the requirements of Art. 83 and 100(b) EPC. Deleting claim 8 was therefore justified on the basis of Art. 83 and 100(b) EPC and so by a ground for opposition. As provided in R. 80 EPC, the ground for opposition (here: Art. 100(b) EPC) did not have to have been invoked by the opponent.