Communications signed by the formalities officer and inviting the appellants to "take note" of the opponents' submissions are not communications of the opposition division within the meaning of Art. 101(1) EPC (Art. 101(2) EPC 1973), which require a period to be fixed for reply (normally four months; see Guidelines E‑VIII, 1.2 – November 2018 version). It is at the discretion of the recipient to reply to this communication if he finds it necessary, having reviewed the significance of the material sent to him. If he intends to reply but for any reason is prevented from doing so within a reasonable period of time, then the appropriate action is to inform the opposition division of his difficulties (see T 582/95).

The boards of appeal have dealt in a series of decisions with the issue of determining what is a reasonable period which provides the recipient of an EPO communication with an adequate opportunity to reply:

The right to be heard enshrined in Art. 113(1) EPC requires that the party concerned be given sufficient time to submit an adequate response if the EPO decides to communicate to a party to proceedings before it an objection raised by another party without an express invitation to reply within a specified time limit. The question regarding what period of time is sufficient for this purpose is a question of fact which has to be answered on the basis of the merits of each individual case. It is to be noted in this context that, as a rule, a time limit set by the EPO should not be shorter than two months (see R. 132 EPC, former R. 84 EPC 1973).

Exceptional circumstances in which a shorter period of time was held to be acceptable were mentioned in T 275/89 (OJ 1992, 126). In this case, the objection was made that the interval between the notification to the patentee of a submission from the opponents and the date the decision was issued was too short to allow the appellant (patentee) to file observations. The board noted that the opposition division had waited for somewhat longer than a month before taking its decision. In the board's view, in the case of a communication which was issued for information purposes only and which did not set a time limit for response, a period of one month (which in the present case was exceeded) sufficed as a rule to comply with the requirements of Art. 113 EPC. Moreover, the documents on which the decision under appeal was based had already been mentioned in the notice of opposition together with an assessment of their substantive and legal significance, so that the decision under appeal was not based on fresh matter.

In T 494/95, the board took the view that the interval of more than one month between the notification of the patent proprietor's reply to the opposition and the date of issuing the decision was sufficient to allow the appellant (opponent) a reasonable opportunity to present his comments, or at least to indicate an intention of so doing, or to request oral proceedings. In the board's view, it was clear from R. 57(3) EPC 1973 (R. 79(3) EPC), from the EPO information "Opposition Procedure in the EPO" (OJ 1989, 417) and from previous decisions that, if oral proceedings did not take place and the decision was based solely on grounds on which the parties concerned had had an opportunity to present their comments, a decision could be taken without further notice upon expiry of the period allowed to the patent proprietor for submitting observations. Here, the board could not see that any procedural violation had occurred, as the decision was neither based on grounds unknown to the appellant (Art. 113(1) EPC), nor was the opposition division invariably obliged under the EPC to set a time limit for the appellant's response to the patent proprietor's observations or to suggest that any such response should be made.

By contrast, another board held in a case involving difficult technical questions that a period of about one month did not provide the appellant with a realistic opportunity to inform the opposition division of his intention to file a substantive reply and to ask for an appropriate time limit for this purpose, let alone to present substantive comments (T 263/93; see also T 494/95).

In T 914/98 the board stated that the seventeen-day period which elapsed between the appellants receiving the reply of the respondents and the handing over of the decision to the EPO internal postal service was manifestly too short to give the appellants an adequate opportunity for comment. According to the board, in view of the case law the appellants could not reasonably have expected a decision to be issued so quickly.