PCT Regional Phase in Europe: A US Guide

Most US companies protect inventions at home first, then file a PCT application to keep foreign options open. By the 31-month deadline, you must decide where to enter national or regional phase. Choosing the European Patent Office is common, but it is not a continuation of US prosecution.

Entering the PCT regional phase in Europe starts a fresh examination under the European Patent Convention. Two issues surprise many US applicants: the strict added-matter rules in Article 123(2) EPC, and the problem-and-solution approach used to assess inventive step.

Added-matter rules at the EPO are stricter in practice than US rules against new matter. Once the application is filed, you generally cannot introduce new technical information, even to distinguish prior art, without violating Article 123(2). That can block amendments that might have been allowed at the USPTO.

The problem-and-solution approach also differs from US obviousness analysis. Instead of asking whether there was a motivation to combine references, the EPO identifies the closest prior art, defines the objective technical problem solved by the difference, and asks whether the solution would have been obvious to a person skilled in the art.

For applicants, the practical effect is that the technical story must already be in the application as filed. New effects, combinations or advantages raised during prosecution may be treated as added matter. This makes the PCT specification, not later argument, the foundation of European claim scope.

Timing and formal steps matter too. Regional-phase entry requires paying the examination and designation fees and, if needed, filing translations within the deadline. Missing the 31-month window usually means loss of rights, with limited restoration options.

A stronger European position starts before the PCT is filed. Align US and European claim strategy early, draft the description to support fallback positions, and brief European counsel before regional-phase entry rather than after the first office action arrives.

The key takeaway is that an international PCT patent application is only a doorway. What happens inside the EPO depends on how well the application was prepared for European rules before the door opened.