Disclaimer Practice At The EPO

The European Patent Office (EPO) uses the term "disclaimer" to refer to a negative feature in a claim of a patent application. Negative features are those which exclude certain subject matter from the scope of protection. While a positive feature in a claim may for instance take the form "wherein the composition comprises X", a disclaimer would take the form "wherein the composition does not comprise X".

Disclaimers can be a useful means of avoiding prior art which cannot easily be overcome by introduction of a positive limitation. However, it is not always straightforward to determine whether a disclaimer can be added to a claim without contravening the prohibition in Article 123(2) EPC¹ against amendments which are not properly based on the disclosure in the application as filed.