You should file foreign patent applications if you plan to sell internationally or if you have a foreign competitor. Important patent applications are typically nationalized in the IP5 jurisdictions: the US, Europe, China, Japan, and Korea.
These countries have large economies with well-functioning patent offices. Some of my clients have also nationalized their PCT applications in additional countries. European applications are examined by the European Patent Office.
When a European patent is allowed, it must be validated in the individual European countries where you want a to protect your invention. A Unitary patent is a relatively recent alternative to individual validations which covers 17 European countries.
Patent prosecution in foreign counties is generally similar to prosecution in the US, but each country has its own process and applies specific laws, necessitating the engagement of a foreign patent attorney.
