Only such oppositions as are deemed to have been filed will be examined for deficiencies under Rule 77(1) and Rule 77(2).
If the formalities officers are not sure whether the opposition in question contains a deficiency under Rule 76(2)(c), they will submit the file to the opposition division for checking. They will do this in particular if the opposition alleges non-patentability under Art. 52, Art. 54 or Art. 56 and the relevant prior art has been made available to the public by means other than by written description, or if taking of evidence has been requested in accordance with Rule 117.
In this connection the opposition division will also examine the extent to which it is necessary for the formalities officer to request the opponent to submit evidence (see D‑IV, 1.2.2.1(v)).
Source: http://www.epo.org/law-practice/legal-texts/html/guidelines/e/d_iv_1_2_2.htm
Date retrieved: 17 May 2021