In substantive examination, the applicant must have an opportunity of presenting his comments on all the grounds invoked against his application.
In opposition proceedings, if the patent is to be revoked, it should be ensured that the proprietor of the patent in particular is given sufficient opportunity to defend himself and, similarly, if the oppositions are to be rejected or if, despite the claims of the opponents, the patent is to be maintained in amended form, the opponents in particular should be given the same opportunity. A decision may be based on grounds indicated in a document from one of the parties, provided the document has been sent to the other party so that he has had an opportunity to comment.
If more than two months have elapsed between despatch of the document "only for information" and the issue of the decision, this generally means that the party has had sufficient opportunity to comment and his right to be heard has therefore not been infringed (T 263/93).
If the patent is to be maintained in amended form, there must be a text of the claims and description which has been approved by the patent proprietor (D‑VI, 2), and the opponent(s) must have had an opportunity to comment on it.