R. 13.4 PCT expressly provides that dependent claims must fulfil the requirement of unity in accordance with R. 13.1 PCT. The EPC makes no comparable express provision. The question has therefore arisen whether dependent claims have to be treated differently under the two provisions. Board of appeal case law on PCT cases has been uniform: the boards have repeatedly confirmed the principle that the requirement of unity must also be met by dependent claims (see inter alia W 3/87, W 2/88, W 30/89, W 32/89, W 26/90, W 8/91 and W 54/91). In EPC cases the boards likewise assume that dependent claims have to meet the requirement of unity. Under the EPC the approach is not as strict as in the case of independent claims, where the examination is always carried out in accordance with the express requirement, but only in those cases where unity could be problematical (see T 140/83 and T 249/89).

In W 8/91 it was decided that, where claims were formally dependent, the ISA had to state expressly why they lacked unity; it was not enough simply to say that this was shown directly by the subject-matter as defined by the ISA.

In W 6/98 the board held that anticipation of the subject-matter of an independent claim might well lead to a situation of non‑unity a posteriori, which however could only be established by showing that there was indeed no unifying novel inventive concept common to all dependent claims. The board noted that lack of novelty of the subject-matter of an independent claim did not automatically lead to a posteriori lack of unity for the claims directly or indirectly appended to said independent claim.

The board in T 129/14 pointed out that, normally, a dependent claim has all the features of its independent claim. If the independent claim comprised one or more special technical features defining a contribution over the prior art, the dependent claim would also comprise them. Hence they would form a single general inventive concept within the meaning of Art. 82 EPC. If the independent claim did not comprise any special technical features defining a contribution over that prior art, e.g. because its subject-matter was not novel, then it would not form any inventive concept. Hence, again no more than one general inventive concept within the meaning of Art. 82 EPC – possibly defined by the additional features of the dependent claim – would result (cf. Guidelines F‑V, 9 – November 2015 version; see now Guidelines F‑V, 2.1, F‑V, 4.2, F‑V, 5 – November 2018 version).