1. Introduction

Article 83 EPC stipulates that the application "shall" (previously "must") disclose the invention in a manner sufficiently clear and complete for it to be carried out by a person skilled in the art. The related ground for opposition is in Art. 100(b) EPC.

The subject-matter of an application must be sufficiently disclosed at the date of the application (see in this chapter II.C.2.), based on the application as a whole (chapter II.C.3.1.), including examples (chapter II.C.5.3.), and taking into account the common general knowledge of the skilled person (chapter II.C.4.). At least one way of enabling the person skilled in the art to carry out the invention must be disclosed (chapter II.C.5.2.), but this is sufficient only if it allows the invention to be performed in the whole range claimed (chapter II.C.5.4.). Parameters must be sufficiently defined (chapter II.C.5.5.). The disclosure must also be reproducible without undue burden (chapter II.C.6.6.); evidence from post-published documents is allowable under certain circumstances (chapter II.C.6.8.).

The distinction between the requirements for sufficiency of disclosure under Art. 83 EPC and clarity of the claims under Art. 84 EPC (chapter II.C.8.) is important, as examination in respect of the requirements of Art. 83 EPC is still permitted during opposition proceedings, whereas in respect of Art. 84 EPC it is limited to cases where there has been an amendment (see also G 3/14 in chapter II.A.1.4.).

The issue of whether the invention is disclosed in a manner sufficiently clear and complete and whether the claims have a basis in the description is a question of fact that has to be answered on the basis of the available evidence and on the balance of probabilities in each specific case. As a rule, the burden of proof lies with the opponent to establish that an invention is insufficiently disclosed (chapter II.C.9.).

Sufficiency of disclosure as applied in biotechnology is considered in this chapter II.C.7., including the issue of broad claims (chapter II.C.7.1.4).

A number of decisions have looked at the monopoly conferred by a patent, how this is linked to the notion of a "technical contribution" and what this means for assessing sufficiency of disclosure; see, for example, the following decisions reported elsewhere in this chapter: T 409/91 (OJ 1994, 653), T 435/91 (OJ 1995, 188), T 1164/11, T 1845/14, T 797/14 and T 2119/14 ; T 2038/19 ; T 2015/20 ; T 1779/21 ; see T 416/14 (as regards a proprietor's argument that there were no potential effects on the competition). The issue of where the line is to be drawn between Art. 56 EPC and Art. 83 EPC was addressed in e.g. T 409/17 (point 3.3.3 of the Reasons), referring to G 1/03 (OJ 2004, 413) and T 1845/14; on this point, see also the following decisions: T 380/05, T 1311/15, T 1079/08, T 862/11, T 2001/12, T 898/05, T 967/09, T 116/18 (OJ 2022, A76) ; T 728/21 ; T 1779/21.