If the patent proprietor, when replying to the notice of opposition, contends that the opposition is inadmissible pursuant to Rule 77(1) and Rule 77(2) because of deficiencies specified by the patent proprietor himself, the opponent concerned must be given the opportunity to submit comments within a period fixed by the formalities officer (normally two months).

If the opposition division concludes that the opposition is inadmissible, it must as a rule first take a reasoned decision, possibly after having held oral proceedings. This decision is appealable. If, on the other hand, on the basis of another – admissible – opposition, an immediate decision can be taken on the rejection of the opposition or oppositions or on the revocation of the patent, the decision on admissibility is to be taken together with this final decision.

If, despite the observations of the patent proprietor, the opposition division concludes that the opposition is admissible, the decision on admissibility is normally to be taken together with the final decision, especially where at least one other admissible opposition exists (see D‑I, 6). If the opposition division is of the opinion that all oppositions are inadmissible, a reasoned decision is to be taken, which is appealable.

An opponent whose opposition has been finally rejected as inadmissible is no longer a party to the subsequent proceedings once this decision becomes final.