The Essentiality Test – Falling Out of Favour at the EPO?

Author: Katherine Banks Ph.D.
Editor:  Hazel Ford Ph.D.

The European Patent Office (EPO) has a notoriously strict approach when considering amendments to patent applications.  If an amendment extends the subject matter beyond the content of the application as filed, then the amendment is unallowable under Article 123(2) EPC.  This is assessed based on the “gold standard” test, which examines whether the skilled person would regard the amended subject-matter to be directly and unambiguously derivable from the application as originally filed. 

Objections under Article 123(2) EPC can arise when features are removed from a claim, broadening the scope of the claim.  However, in some cases, the EPO has taken a more lenient approach when considering the removal or replacement of non-essential features. The “essentiality test” was established in EPO Board of Appeal Decision T 331/87, which held that the removal or replacement of a feature would not be considered added-subject matter if it satisfied three criteria:

  • the feature is not described as being essential in the application as filed;
  • the feature is not indispensable to the function of the invention; and
  • the removal or replacement requires no real modification of other features to compensate for the change.

Some recent decisions have moved away from the use of this essentiality test. In the recent decision T 1852/13, the applicant argued that a claim amendment was permissible under the essentiality test.  The Board of Appeal held that the essentiality test was inconsistent with the “gold standard” test for determining if Article 123(2) EPC had been contravened. The inconsistency between the two tests arose from whether the application disclosed the non-essentiality of the feature (the gold standard test), rather than simply not disclosing the essentiality of the feature (the essentiality test).

The Board reasoned that while the essentiality test can provide useful information in some cases, it cannot replace the gold standard test. They concluded that all amendments should be assessed under the gold standard, rather than the essentiality test.

The Board of Appeal refused the applicant’s request to refer questions to the EPO’s Enlarged Board of Appeal to clarify this inconsistency, because in this particular case they considered that both tests would lead to the same answer. Therefore, we are not likely to have a definitive answer any time soon.

This decision reinforces the general movement of the EPO towards the gold standard as an overriding test when considering amendments during prosecution, and suggests a more restrictive view on some types of post-filing amendment.  When drafting a patent application, it should be carefully considered whether all features of the independent claims are necessary.  It may be difficult, or in some cases impossible, to remove non-essential features from a claim during prosecution before the EPO.


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