The question of whether and to what extent a claim broadened beyond the disclosure of a priority document can validly claim a right of priority has been a subject of a considerable recent interest, as it may have an effect on many European patents and patent applications. The approach of the Boards of Appeal of the European Patent Office in addressing this problem has not been consistent. Some Boards of Appeal adopted a very strict approach, holding that a generalized claim containing a broader term or formula is not entitled to a priority date, if the priority document only discloses a specific example falling within the broader term or formula of the claim (see for example T 1877/08, T 476/09, T 1443/05 and T 1127/00). This strict approach led to situations in which, for example, a published divisional application, becoming Art. 54(3) EPC prior art, destroyed the novelty of the claims of its own parent application that have been broadened beyond the disclosure of the priority document (a so called “poisonous divisional”). Some other Boards of Appeal took a less restrictive approach, indicating that a generalized claim might be entitled to a partial priority (see for example T 1222/11, T  571/10).

In case T 557/13 concerning European patent EP 0 921 183, which as a divisional application based on EP 95923299.2 and clams priority of GB 9411614, the Board of Appeal 3.3.06 was faced with the issue of “partial priority”. In opposition proceedings, the opposition division revoked the patent in suit, on the basis that claim 1 of the patent in suit, which had been broadened over the priority document, was not entitled to the priority date. This had the result that the parent application was cited as prior art under Art. 54(3) EPC and it was held that one specific example disclosed in the parent application destroyed the novelty of the more general claim 1 of the patent in suit. The patent proprietor appealed this decision.

In the preliminary opinion dated November 26, 2014 the Board of Appeal stated that:

"[…] the issue of novelty apparently may hinge on the question of whether or not, under the circumstances addressed above, the patent in suit can validly claim a right of priority as regards the use of the product of Example 1 as cold flow improver, considering in particular that said use is merely embraced by the more generic definition of the invention according to Claim 1 at issue, rather than being clearly defined as a distinct alternative of the invention defined in Claim 1" (see point 4.2.2 of the preliminary opinion of November 26, 2014).

The Board of Appeal also noted that

“[…] the potential legal uncertainty perceived by the parties with regard to this point of law, which they appear to consider as an important one, might require clarification by means of a referral to the Enlarged Board of Appeal […]” (see point 5 of the preliminary opinion of November 26, 2014).


During oral proceedings, the Board of Appeal announced their intention to refer questions to the Enlarged Board of Appeal, although the exact questions will only be known after the written decision is issued.

The answers of the Enlarged Board of Appeal on the question of partial priority may have a significant impact on everyday practice, since it is not uncommon to file a subsequent application that is broader than its respective priority application, for example in order to cover further developments of the invention within the priority year.

The electronic register of the EPO related to EP 0 921 183 can be accessed at https://register.epo.org/application?number=EP98203458&lng=en&tab=doclist

Should you have any questions, please feel free to contact Burger@mueller-bore.de