In T 201/83 (OJ 1984, 481) it was stated that the test for compliance with Art. 123(2) EPC 1973 was basically a novelty test, i.e. no new subject-matter may be generated by the amendment (see also T 136/88). T 17/86 (OJ 1989, 297, Corr. 415) added that novelty could be found in a limitation, the addition to a claim of a further feature, or even in the absence of one of the elements of a device. In G 2/10 the Enlarged Board held that after the amendment the skilled person "may not be presented with new technical information".
The boards have seldom expressly applied the novelty test in their recent case law, but it was referred to in e.g. T 60/03, T 1374/07, T 2202/08, T 2270/09; according to T 2537/10, the novelty test is no longer relevant for the assessment under Art. 123(2) EPC. However, reference is still made to this test in the 2015 version of the Guidelines (H‑IV, 2.2), at least where the amendment is by way of addition.
Decision T 194/84 (OJ 1990, 59) related to amendments leading to the generalisation of the subject-matter of an application or to the omission of a feature. The patentee had taken the view that the amendment was admissible because the original application could properly be cited against the novelty of a more generic claim to cellulose fibres. The board took the view that this approach was based on a misapplication of the novelty test. The test for additional subject-matter corresponded to the test for novelty only in so far as both required assessment of whether or not information was directly and unambiguously derivable from that previously presented in the originally filed application or in a prior document respectively. An amendment was not allowable if the resulting change in content of the application, in other words the subject-matter generated by the amendment, was novel when compared with the content of the original application or, looked at another way, if the said change in content would be novelty-destroying for a hypothetical future claim when the original content would not be. It was important that it was the change in content which was tested, i.e. the amended content minus the original content, so that the test was applicable to amendment by generalisation or omission of a feature.
T 133/85 (OJ 1988, 441) pointed out that care was necessary when applying the law relating to novelty to questions which arose in relation to Art. 123(2) EPC 1973. In T 177/86 the novelty test was described as "not very useful" for examining the admissibility of broadening a claim (see also T 150/07 for a case where the preferred embodiments of an invention were combined with the more general teaching thereof).
T 118/89 took a reserved attitude to the novelty test and observed that the allowability of amendments during the grant procedure could be determined without reference to the state of the art simply by comparing the protection sought on the basis of the current claims with the disclosure in the application as filed. There was therefore no objective need to carry out new or modified novelty tests.
In T 187/91 (OJ 1994, 572) the board conceded that there was clearly a close conceptual correlation between the assessment of novelty and the assessment of what was an allowable amendment under Art. 123(2) EPC 1973. It further explained, however, that two considerations which underlay Art. 123(2) EPC 1973 were different from those that underlay Art. 54 EPC 1973: firstly, a reader of an application published pursuant to Art. 93(1) EPC 1973 after 18 months would be informed of the maximum extent of its subject-matter and therefore its maximum content some time before the text of the application including the claims was finalised, having regard to the drawing up of the European search report and the subsequent examination of the application. Secondly, the relationship between the claims and content of the European patent application was determined by the idea that, after appropriate amendment if necessary, the granted claims should give a fair protection for the inventive subject-matter contained in the application as filed.
In T 288/92 the board considered that the examination of the allowability of an amendment according to Art. 123(2) EPC 1973 was directed to the process of "derivation" (see also T 383/88), as distinct from a simple comparison of the scopes of amended and unamended subject-matters. In the view of the board this provided a definitive method for deciding the allowability of an amendment. Any other "test", such as the "novelty test", necessarily posed hypothetical questions.
However, in T 873/94 (OJ 1997, 456) the board pointed out that where a proposal for amending an application involved the addition of a limiting feature to a claim, applying a "novelty test" was not appropriate for determining whether or not the amendment complied with Art. 123(2) EPC 1973. Following G 1/93 (OJ 1994, 541), the board pointed out that the underlying idea of Art. 123(2) EPC 1973 was clearly that an applicant should not be allowed to improve his position by adding subject-matter not disclosed in the application as filed, which would give him an unwarranted advantage and could be damaging to the legal security of third parties relying on the content of the original application. In the light of these considerations the addition to a claim before grant of an undisclosed limiting feature might or might not violate Art. 123(2) EPC 1973, depending on the circumstances.