The unforgiving gold standard: Why deleting a feature can add matter at the EPO (T 0422/23)

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Rose Hughes

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Sep 29, 2025, 11:39:17 AM (6 days ago) Sep 29

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The unforgiving gold standard: Why deleting a feature can add matter at the EPO (T 0422/23)

Dr Rose Hughes Sunday, September 28, 2025 - added matter, epo, patents, PatKat, Rose Hughes

In the EPO gold standard test for added matter, what is deleted can be just as problematic as what is added. The unforgiving gold standard test for added matter requires that any amendment, including the deletion of a feature, must be directly and unambiguously derivable from the original application. The Board of Appeal in the recent decision of T 0422/23 rejected the Opposition Division's finding that a deleted feature was not essential (the "three point essentiality test"). Following the general direction of EPO case law, all that mattered for the Board of Appeal was whether the invention without the feature was directly and unambiguously disclosed in the original application. For the Board of Appeal, this did not require applying the three point essentiality test, because the outcome should be the same as the gold standard test. On the basis of this decision, the EPO's gold standard test seems to be only getting stricter with fewer opportunities for nuance.

Legal background: The 'gold standard' for added matter

At the EPO, the bar for amending an application or patent is infamously high. A European patent application or patent may not be amended in such a way that it adds subject matter which extends beyond the content of the application as filed (Article 123(2) EPC). The established case law for assessing added subject matter takes the form of the gold standard test, which asks whether the subject matter of the amendment can be derived directly and unambiguously by a skilled person from the application as filed as a whole. For divisional applications, the same principle applies with respect to the earlier application as filed (Article 76(1) EPC). Whilst most jurisdictions have similar provisions, the EPO approach to added matter is extraordinarily strict. Indeed, added matter may result from as little as a misplaced comma in the claims, as in the catastrophic comma loss cases (IPKat, IPKat).

Golden

Importantly, the test for novelty at the EPO forms the other side of the coin of the added matter test. In particular, if a disclosure, selection or amendment is novel, then it is also added matter (and vice versa). The case law on novelty and added matter at the EPO is therefore inextricably linked, and the application of the gold standard test is relevant to both. In recent years, the Boards of Appeal have repeatedly emphasised that the gold standard test supersedes any other "special" tests that have previously been suggested for assessing novelty and added matter for certain types of inventions, including selection from lists (IPKat) and inventions relating to the increased purity of a known compound (IPKat).

Case background: The case of the disappearing battery

The patent in question in the present case (EP3571944), owned by Joyetech (Changzhou) Electronics Ltd., related to an intelligent controller for an electronic cigarette. The invention aimed to provide a controller that could detect the electrical condition of the atomizer's heating wire, for example, to determine if there was a short-circuit or open-circuit. The Opponents were anonymous behind strawperson oppositions.

At Opposition, the Opposition Division (OD) decided to maintain the patent on the basis of an auxiliary request. The independent claim of this request defined an electronic cigarette comprising an intelligent controller with various modules: a switch, a voltage acquisition module, a control module, and a display module. Importantly, the original application (of which the case in question was a divisional) described and claimed an intelligent controller that also comprised a battery, which was defined as being electrically connected to the other modules to supply them with power. In the version maintained by the Opposition Division, the feature of the battery had been removed from the definition of the intelligent controller.

The Opponents appealed the OD decision, arguing inter alia that the omission of the battery feature constituted added subject matter. The OD had concluded that the battery could be omitted without violating Article 76(1) EPC because the language relating to the battery was not "functionally or linguistically associated with the remaining features". The OD specifically applied the so-called "three point essentiality test" with respect to the removal of features. According to this test, an amendment removing a feature from a claim does not add matter if:

(i) the replaced or removed feature was not explained as essential in the originally filed disclosure;

(ii) the skilled person would directly and unambiguously recognise that the feature is not, as such, indispensable for the function of the invention in the light of the technical problem the invention serves to solve; and

(iii) the skilled person would recognise that the replacement or removal requires no modification of one or more features to compensate for the change (it does not in itself alter the invention).

Applying this test, the OD found that the removal of the battery feature did not add matter on the basis that the presence of a battery would not be recognised as an essential feature by a skilled person, and that removing this feature from the claim would not require modification of any of the remaining features. The OD further noted that, applying also the gold standard test, it would be evident to a skilled person that the language of the claim in the original application relating to the battery was "not functionally or linguistically associated with the remaining features of the claim", and so could be omitted without adding matter.

Always the gold standard

On appeal, the question before the Board of Appeal was whether the OD had properly applied the test for added matter with relation to the omission of the battery feature. Unfortunately for the Patentee, the Board of Appeal did not follow the OD reasoning. The Board of Appeal particularly rejected the argument that the battery was a "severable" feature. Instead, in the view of the Board of Appeal, the battery was "without a doubt originally defined to be a part of the electronic controller" The Board of Appeal also found the OD's conclusion on the functional connection hard to follow, stating: "the battery is defined there as being connected to the switch module, the voltage acquisition module, the control module and the display module and moreover as being configured to supply working voltage power to these elements, which is without doubt its function. Therefore, the battery is originally disclosed functionally [as well as structurally and indeed linguistically] associated with those elements and presented as being an integral part of the intelligent controller."

For the Board of Appeal, it was therefore clear that the omission of the battery feature added matter. The original application disclosed an intelligent controller comprising a battery connected and functioning in a specific way. As such, an intelligent controller without such a battery could not be said to be disclosed, directly or unambiguously. For the Board of Appeal therefore, the claims thus contained added subject matter, and the main request on appeal was not allowable.Final thoughts

The EPO's "gold standard" for added matter is notoriously unforgiving, and often far stricter than similar tests applied in (any?) other jurisdictions (IPKat). The present case highlights how the gold standard may be applied with equal force to the removal of features as it does to their addition or combination. In line with the recent case law rejecting special tests that add nuance to the gold standard for different subject matter or inventions, the Board of Appeal relied solely on the gold standard test instead of following the OD approach of evaluation according to the three point essentiality test. For this Kat, T 0422/23 is perhaps a warning that the EPO may consider most features present in an original independent claim as "essential", or at the very least that arguing for the non-essentiality of a feature will be an uphill battle. From the drafting perspective, therefore, the requirements of the EPO teach us to be ruthless with deleting inessential features from the independent claims before the application is filed.