It is at the opposition division's discretion whether to admit late‑filed documents (Art. 114(2) EPC; see chapter IV.C.4.1. above). According to settled case law, it must first examine them as to their relevance. Late‑filed facts and evidence and supporting arguments should only exceptionally be admitted into the proceedings if, prima facie, there are reasons to suspect that such late-filed documents prejudice the maintenance of the European patent in suit (see, in particular, T 1002/92, OJ 1995, 605; see also T 1643/11, T 2443/12; and in this chapter IV.C.4.5.3 "Prima facie relevance").

As to whether and, if so, to what extent opposition divisions can or must consider other criteria too, with the result that even prima facie relevant documents may not be admitted in certain cases, the boards have taken various different approaches.

According to one of those approaches, the principle of examination by the EPO of its own motion (Art. 114(1) EPC) takes precedence over the possibility of disregarding facts or evidence not submitted in due time. This follows from the EPO's duty towards the public not to grant or maintain patents which it is convinced are legally invalid (T 156/84, OJ 1988, 372; T 2542/10; T 1272/12). Accordingly, the main criterion for deciding on the admissibility of late-filed documents and evidence is their relevance, i.e. whether they are decisive (relevant) for the outcome of the case (see T 258/84, OJ 1987, 119; T 892/98; T 605/99). Some decisions assess the relevance in relation to other documents already in the case (e.g. T 932/99, T 482/01, T 927/04; see however T 1652/08 and T 66/14 rejecting this definition). If the document is relevant it must be admitted into the case and taken into account (T 164/89, T 1016/93).

In addition, in landmark decision T 1002/92 (OJ 1995, 605) the board held that the principles set out by the Enlarged Board in G 9/91 and G 10/91 (OJ 1993, 408 and 420) with regard to the admissibility of fresh grounds of opposition (see chapter IV.C.3. above) are also generally applicable to late-filed new facts and evidence in support of grounds of opposition already presented in the notice of opposition. Accordingly, in proceedings before the opposition divisions, late-filed facts, evidence and related arguments which go beyond the "indication of the facts, evidence and arguments" presented in the notice of opposition pursuant to R. 55(c) EPC 1973 should only exceptionally be admitted into the proceedings if, prima facie, there are clear reasons to suspect that such late-filed material would prejudice the maintenance of the European patent in suit. The board saw the consideration of relevance as the principal factor governing the exceptional admissibility of late filed new facts, evidence and related arguments in proceedings before the opposition division. For the more restrictive and stringent criteria in proceedings before the boards of appeal, see chapter V.A.4.13. below.

Many decisions have affirmed T 1002/92 (for late submissions in opposition proceedings see e.g. T 481/99, T 481/00, T 1643/11, T 2438/13, T 710/15).

However, in many earlier decisions, too, the relevance of late-filed documents was no longer viewed as being the only decisive criterion for admitting them. Other criteria, such as how late the documents were, why they had been submitted late and whether their submission constituted a procedural abuse or whether admitting the late-filed documents could lead to an excessive delay in the proceedings, were also held to be decisive (see T 534/89, OJ 1994, 464; T 17/91, T 951/91, OJ 1995, 202; T 1019/92, T 481/99, T 1182/01, T 927/04, T 1029/05, T 1485/08, T 2542/10, T 1272/12, T 1883/12, T 1271/13).

For decisions on the exercise of discretion by opposition divisions, see in this chapter IV.C.4.5.3 to 4.5.5; for "Criteria for considering late-filed facts and evidence" in appeal proceedings, see chapter V.A.4.13. below.