As a rule, each party bears the burden of proof for facts which it alleges. In the specific case of internet citations of prior art cited by the EPO, the burden of proof thus lies with the EPO. If however, the EPO is satisfied that, on the balance of probabilities, an internet citation constitutes prior art, it is then up to the party to prove otherwise (ex parte cases T 2227/11, T 1589/13).

In ex parte case T 545/08 the board stated that the commercial website from which document D1 was retrieved could not be considered, at least not without further investigations, as a source generally deemed to provide reliable publication dates, such as the websites of scientific publishers. It concluded that the examining division was not entitled to consider document D1 as prior art in its first substantive communication without providing further explanations and evidence as to the document's public availability before the priority date (see also T 1961/13). Thus, the objection was not properly raised. It could not generate an obligation on the applicant's side to submit evidence against the assumed publication date in the written proceedings (see the observations on the burden of proof in T 545/08, points 12 and 13 of the Reasons, see also T 1066/13).