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In T 1852/13, the so-called ‘essentiality test’ was analysed in detail. Questions were raised as to whether this test is in compliance with the Gold Standard for assessing added subject-matter following claim amendments.


The EPO’s Boards of Appeal have previously used the ‘essentiality test’ to determine whether after the deletion of a claim feature the remaining subject-matter is still in compliance with the content disclosed in the application-as-filed.

The essentiality test states that the removal or replacement of a feature is not to be considered added subject-matter if it satisfies three criteria:

  • the feature is not described as essential in the application-as-filed;
  • the feature is not, as such, indispensable to the function of the invention in light of the objective technical problem solved; and
  • the removal or replacement of the feature requires no real modification of other features to compensate for the change.

This test has often been described as a lenient approach for assessing added subject-matter, and it has been criticised in a number of Decisions since it was first described in T 331/87.


The Board in T 1852/13 reviewed the history of the ‘essentiality test’, as well as the criticism resulting from its application.

The Board ultimately found that the test is in conflict with the Gold Standard for assessing added subject-matter following claim amendments. The Gold Standard (from G2/10) states that any amendment must lead to subject-matter that the skilled person would derive directly and unambiguously, using his common general knowledge, from the application-as-filed.

An inconsistency between the two tests arose from whether the application disclosed the non-essentiality of the feature (Gold Standard) or simply didn’t disclose the essentiality of the feature (essentiality test). The Board concluded that the Gold Standard is a superior test, and stated that “the essentiality test should not be used anymore”.


Due to the outcome of the case being the same no matter which test was applied, the Board refused to refer any questions to the Enlarged Board of Appeal.

Thus, although this Decision provides a significant blow to the validity of the ‘essentiality test’, it has not provided a definitive answer as to whether the test is out-dated and irrelevant.


Our articles are for general information only. They should not be considered specific legal advice, which is available upon request. All information in our articles is considered to be accurate at the date of publishing.


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