The international application must relate to one invention only or to a group of inventions so linked as to form a single general inventive concept. [Art. 17(3)(a); Rule 13.1; ]

When determining unity of invention, a finding of lack of clarity of the claims is on its own not sufficient grounds for a finding of lack of unity.[Art. 6; ]

Normally, too, the sequence of the claims should not have an impact on the determination of unity of invention. However, it will have an impact on which invention is to be considered the first invention mentioned in the claims (see GL/PCT‑EPO F‑V, 8.2).

Moreover, the fact that the claimed separate inventions belong to different groups of the classification is not in itself a reason for a finding of lack of unity.

An application may contain claims of different categories, or several independent claims of the same category. This is not in itself a reason for an objection of lack of unity of invention if the requirements of Rules 13.1 to 13.3 are otherwise met.

With regard to substantive criteria, unity of invention is examined in search and substantive examination in both European and PCT procedures according to the same principles. This does not apply to the respective procedures themselves, where significant differences exist (see also GL/PCT‑EPO B-VII).[Art. 150(2) EPC; ]