EPO opposition vs appeal

An opposition is a first‑instance, administrative procedure in which the validity of a granted European patent is re‑examined. It is handled by an Opposition Division (OD), typically composed of three technically qualified examiners, at least two of whom must not have taken part in the proceedings for grant of the patent in question. The panel is occasionally supplemented by a legally qualified member.

The OD engages in a full fact‑finding exercise: parties may file new evidence, arguments, and claim amendments, particularly at earlier stages, and the OD assesses the case a fresh on its merits. Facts and evidence filed after the initial nine-month opposition deadline may only be admitted into the proceedings if they are prima facie relevant, i.e. if they would change the envisaged decision, or because the subject of the proceedings has changed.

In contrast, an EPO appeal is a judicial review of the OD’s decision rather than a re‑run of the opposition. Appeals are heard by a Board of Appeal, which is independent from the examining and opposition departments and usually has two technical members and one legal member, sometimes enlarging to five (three technical, two legal) for complex cases.

The appeal procedure is governed by much stricter formal rules. The notice of appeal (and accompanying fee) must be filed within two months of notification of the contested decision, and the statement of grounds must be filed within four months.

After that point, the Boards operate under stringent admissibility criteria, and new facts, arguments, or evidence are admitted only in exceptional circumstances; parties are generally expected to rely on the case they presented during opposition. The Board’s task is to review whether the OD committed a substantive or procedural error, whether it properly applied the EPC, and whether the decision can be upheld. While the Board may re-evaluate evidence, its review is more focused and disciplined than that of the OD.

Ultimately, the Board may uphold the decision, set it aside, or remit the case for further examination, but the appeal remains a structured judicial oversight mechanism, not an opportunity to build an entirely new case.