Under Art. 114(1) EPC, the EPO is obliged to examine the facts of its own motion, and in doing so, it is not restricted to the facts, evidence and arguments provided by the parties and the relief sought. In T 223/95 the board emphasised the character of the post‑grant opposition proceedings under the EPC, which were in principle to be considered as contentious proceedings between parties normally representing opposite interests, who should be given equally fair treatment. It was the responsibility of the opponent himself to present to the opposition division the facts, evidence and arguments in support of the grounds on which the opposition was based.

According to Art. 114(2) EPC, however, the EPO may disregard facts or evidence which are not submitted in due time by the parties concerned. Interpretation of Art. 114 EPC therefore requires an analysis of the inter-relationship between its paragraphs 1 and 2. In T 122/84 (OJ 1987, 177) the board summarised the historical development of the principle of ex officio examination with regard to late submission on the basis of the "travaux préparatoires" to the EPC 1973. A solution it found compatible with this principle was to leave it to the discretion of the department concerned whether or not to examine facts or evidence not submitted in due time, rather than ruling out such examination altogether.

For appeal proceedings the boards have highlighted that a rigid rule excluding all new evidence might lead to injustice and unfairness in some cases and would not be compatible with the principles of procedural law generally recognised in the Contracting States (J 5/11, J 6/14, T 598/13). That applies a fortiori to opposition proceedings.

The discretionary power under Art. 114(2) EPC is clearly conferred on the EPO departments only to ensure that proceedings run smoothly and to forestall tactical abuse (T 273/84, OJ 1986, 346).

For proceedings at first instance, R. 116(1) EPC provides that, when the summons to oral proceedings is issued, a final date for making written submissions in preparation for the oral proceedings must be fixed. New facts and evidence submitted after this date need not be considered, unless admitted on the grounds that the subject of the proceedings has changed. This provision does not act as an absolute bar to admitting late submissions; instead, its very wording shows that it leaves room for discretion (T 798/05; see also T 2102/08, T 1253/09).