Before grant of a European patent there are restrictions on the permitted amendments set out in Article 123(2) which reads as follows:
A European patent application or a European patent may not be amended in such a way that it contains subject matter which extends beyond the content of the application as filed.
This rule also applies after grant.[1] In this case, however, a further limitation applies, namely that the claims cannot be broadened.[2] However, a change of category, for example from a claim to a composition as such to a particular use is permitted if the change does not result in anything that would not have been an infringement of the unamended patent becoming an infringement of the amended patent.[3] On the other hand it has been held that if a claim has been granted erroneously to a method of medical treatment, it is not possible during opposition proceedings to change the category of claims to a "device" since that would have the effect of broadening the claims.[4] However, amendment of a granted claim to replace an inaccurate technical statement which is evidently inconsistent with the totality of the disclosure of the patent by accurate statement of the technical features involved is permitted.[5]
