The main provision establishing the right to amend a patent
application or a patent is Article 123 EPC, which includes
- The European patent application or European patent may be
amended in proceedings before the European Patent Office, in
accordance with the Implementing Regulations. In any event,
the applicant shall be given at least one opportunity to
amend the application of his own volition.
- The European patent application or European patent may
not be amended in such a way that it contains subject-matter
which extends beyond the content of the application as
- The European patent may not be amended in such a way as
to extend the protection it confers.
Paragraph (1) includes a restriction in time, that is when
amendments may be carried out, and it allows amendments to the
European patent application or the European patent in all
proceedings before the European Patent Office (EPO); this means
that amendments may be permitted during examination, opposition
and appeal proceedings. Paragraph 1 further specifies that the
applicant must be given at least one opportunity to amend the
application of his/her own volition. This means that, even when
no objections are raised in the search opinion (whereby no
invitation to correct any deficiencies is put forward), the
applicant has the right to file voluntary amendments, without
the need to ask for the consent to the examining division.
Paragraph 2 limits the impact of the amendments on the
European patent application or the European patent, in the
sense that the amendments cannot introduce subject-matter not
disclosed in the application as filed.
Paragraph 3 applies to granted European patents and limits
the impact of the amendments by prohibiting any extension of
the scope of protection conferred by the patent as granted.
The legal framework for amendments further includes several
auxiliary provisions, such as those contained in Article 14
paragraph 2 (correction of errors of translation), Rule 137
(time frame for carrying out amendments), Rule 138 (different
amendments for different states), Rule 139 (correction of
errors in documents filed with the EPO) and Rule 140
(correction of errors in decisions of the EPO).
Corrections versus amendments
When modifications are to be carried out on a European
patent application or European patent, the distinction between
"corrections" is very important. This is
because it affects the choice of the provisions under which the
request for modification should be asked, either Article 123
(with relating Rules 137 and 138 and specific deadlines for
amendments) or Rule 139 (and in that case Article 14(2), anyway
with no deadlines for making the corrections).
Unfortunately, the EPC neither defines the terms "amendment"
and "correction", nor establishes a relationship between
Fortunately, through the EPO case law (Decision J8/80), it
is possible to figure out meaningful definitions for
"amendment" and "correction".
On one hand, an "amendment" to a document should be
interpreted as a change of mind of the applicant/proprietor or
as a subsequent development of plans for improving the
On the other hand, a "correction" of a document should be
interpreted as a restoration into conformity with the true
intention of the applicant/proprietor, for example for putting
right an incorrect statement or adding omitted matter. Hence,
dealing with an "unexpressed volition" ("an intention"), in
principle a correction might include something not disclosed in
the filed documents (such as an omitted priority claim). For
this reason, the proposed correction must be examined very
carefully, in order to ascertain whether it hides a change of
mind of the applicant/proprietor or it represents an actual
restoration of the document into conformity with his true
intention. Furthermore, a correction is assessed differently,
depending on the fact that it affects the application/patent
(claims, description, drawings) or collateral documents (such
as the request for grant).
Where errors or mistakes concern documents other than the
claims, description or drawings (for example, a missing
priority claim), the proposed correction may be derived from a
global assessment of the circumstances involved and it should
be presented to the EPO in such a way that the latter is able
to check and be convinced that: (i) a mistake was made; (ii)
what the mistake was; and (iii) what the correction should
Instead, if the claims, description or drawings are
concerned, the error must be obvious, in the sense that the
skilled person must be in no doubt that the information is not
correct and, at the same time, in no doubt on what the
correction is ("is" and not "should be"). In this regard, a
good rule of thumb is the following: if the error becomes
apparent only in the light of the proposed correction, then the
correction is not self-evident and must be ruled out (G3/89).
Therefore, at the end of the day, the correction of errors in
the claims, description or drawings must have a declaratory
Attention should be paid to the fact that an apparently
obvious mistake might not be so obvious indeed.
For example, assume that the description contains the
following expression: 1+1=3. Probably, the most of us would
immediately propose the following correction: 1+1=2.
Are we sure that such a correction is self-evident, which
means that it has a declaratory nature?
Not so sure. What about these: 1+2=3 or 2+1=3 or
If more than one possibility of correction can be foreseen,
then the error is not that obvious. In this situation, the
proposed correction might still be admitted, but as long as it
is proposed as an amendment complying with article 123 (and not
as a simple correction!), meaning that the applicant/proprietor
has to prove that the amendment is derivable from the
application as filed.
The disclosure test or gold standard for assessing the
extension of subject-matter
The EPO is known for being very strict in assessing the
provision of Article 123(2) EPC.
The principle for such a strict interpretation can be found
in the task of the EPO to guarantee legal certainty to third
parties, who can rely only upon the application as filed, being
the "file estoppel" not available under the EPC.
Furthermore, the EPO aims to prohibit unwarranted advantages
for the applicant, who is supposed to be rewarded with an
exclusive right for what was invented at the time of filing and
not afterwards. In this regard, the EPO wants to prevent the
applicant being rewarded for an invention made ex-post, for
example after a critical review of the state of the art that
usually emerges during examination or post-grant
In view of these principles, the case-law of the EPO Boards
of Appeal (G11/91; G3/98; G1/03; G2/10) has established the use
of the so-called disclosure-test or gold standard.
Hence, for the time being, the disclosure-test is the
generally accepted test for any amendment.
Getting down to brass tacks, the formulation of the
disclosure-test is the following: an amendment should be
regarded as introducing subject-matter that extends beyond the
content of the application as filed, if the overall change in
the content of the application results in the skilled person
being presented with information that is not directly and
unambiguously derivable – seen objectively and
relative to the date of filing – from the whole
content of the application as filed, even when account is taken
of any feature that is implicit to a person skilled in the art
using common general knowledge.
A good way to appreciate the disclosure-test is to cut it
down into single concepts, with the help of the WH-questions.
Let's get the analysis started:
An amendment should be regarded as introducing
subject-matter that extends beyond the content of the
application as filed, if:
What: the overall change in the content of the
application, that is the outcome of an amendment in
terms of the technical information presented;
Who: the skilled person being
presented with information, which means that the outcome
of an amendment must be assessed from the point of view of
the skilled person;
How: information which is not
directly and unambiguously derivable, which means that
the outcome of an amendment must be a priori
straightforward and explicit in view of the disclosed
invention; in other words, if additional technically relevant
information become apparent to the skilled person after the
amendment is carried out, then the amendment must be ruled
Where: from the whole content of the
application as filed, which means that the outcome of an
amendment must be found in the application as filed and it
cannot be derived from the priority document, the abstract,
the title or the documents cross-referenced in the
description (in the latter case, unless no doubt exists for
the skilled person that such documents are part of the
When: seen objectively and relative
to the date of filing, that is the content of the
application must be read bearing in mind the technical
knowledge and the state of the art available at the date of
filing, and not afterwards. In other words, if a new
technology has been invented after the date of filing, none
of its technical implications can be kept in the background
for interpreting the content of an application/patent. In
this regard, the so-called common general knowledge can be
used to interpret the teaching of the technical information
presented in the application/patent and to put them in the
context, but it cannot be used to bridge any gap in the
In view of the concepts embedded in the disclosure-test, it
emerges that the assessment of amendments must be carried out
focusing on the actual teaching conveyed by the original
disclosure, the structure of the claims not being detrimental
to what is really disclosed (T2619/11).
As an immediate consequence, the literal support is not
required (T667/08, T583/09, T2296/08), contrary to the
misconception widely spread outside Europe.
Finally, it is to be noted that, besides the amendments, the
disclosure-test also applies to the assessment of:
- the content of prior art documents in order to evaluate
their impact on the patentability of a claimed
- the validity of a priority claim, namely to ascertain
whether the features of an invention can be found in the
priority application; and
- the validity of a divisional application (Article 76(1)
EPC), namely to ascertain whether the content of the
divisional application can be found in the parent
Amendments and extent of the patent protection
As already cited, paragraph 3 of Article 123 states: "The
European patent may not be amended in such a way as to extend
the protection it confers."
This provision applies to claims, description and drawings,
both in opposition and limitation proceedings before the
The principle at the basis of this provision is to give
ultimate legal certainty to third parties, so that to exclude
that an activity or a product not infringing the patent before
the amendments does actually infringe the patent after the
amendments have been carried out.
Combining the provisions of paragraphs 2 and 3 of Article
123, the following awkward situation occurs.
Let's assume that a limiting feature that extends the
subject-matter is introduced in a claim during the examination
and that the patent then is granted. Now, let's also suppose
that the feature should be removed in subsequent opposition
proceedings, because it is duly contested by the opponent. But
pursuant to paragraph 3 of Article 123, the removal of the
feature – which should actually be removed! –
is not permitted.
This is the so-called inescapable trap of Article
123(2)-(3): with or without the removal, the patent is
In fact, if the feature were not removed, the patent would
contain subject-matter that extends beyond the content of the
application as filed. On the other hand, if the feature were
removed, the scope of patent protection would be extended.
The trap is caused both by the examiner, who granted the
patent, and by the applicant who introduced fresh
Hence, in opposition proceedings, bear in mind that an
attack on the ground that the patent contains fresh
subject-matter can be strengthened by the use of the provision
under Article 123 paragraph 3.
A similar situation occurs when, during examination, a first
feature in a claim is replaced with a second feature that
extends the subject-matter and nevertheless the patent is
granted. In opposition, the restoration of the first feature,
in place of the second one, is not permitted, because the
amended claim would cover a different and alternative
embodiment with respect to the embodiment claimed in the patent
as granted, thus extending the scope of protection of the
Therefore, whenever possible, it is strongly suggested to
carry out amendments by grouping together different claims,
rather than to develop new esoteric wording for defining an
In view of this, both the deletion of a feature and an
intermediate generalisation are far less risky: should the
subject-matter extend beyond the application as filed, the
solution is merely to restore the deleted feature or to add the
features previously left out (intermediate restriction, see
above), thus limiting – and not extending
– the protection conferred by the patent.
Tips to take away
It is of the utmost importance when drafting the European
patent application to pave the way towards reliable amendments,
should there be the need to circumvent prior art cited during
examination or post-grant proceedings.
First of all, our suggestion is to disclose all the main
features of the invention, even though they are not actually
claimed. Whenever possible, each feature should be introduced
stand-alone, preferably in the "summary of invention", for
avoiding any objection of "intermediate generalisation".
Possible wording is "according to one aspect…",
"according to a further aspect…", "As a general concept,
the invention comprises the following aspect…" and
similar. In my opinion, the word "aspect" is better than
"embodiment" – at least in the summary –
because "embodiment" might take for granted the presence of a
mutual relation among other features previously introduced.
When the figures are described, which surely illustrate
"embodiments", a good wording might be "the drawings illustrate
embodiments of the disclosure and, together with the
description, serve to explain the principles of the
Secondly, a "good" set of dependent claims, in term of scope
of protection, clarity and dependency, should be drafted:
grouping together the claims is easy and prevents any objection
under Article 123 paragraphs 2 and 3.
Finally, avoid any statement that, even implicitly, might
depict a feature as an essential feature for an embodiment;
should that be the case, you may want to delete the feature
from an embodiment, but, if that feature is perceived as
essential, the deletion would be impossible (see
||Marco graduated in
aerospace engineering at the Polytechnic University of
Milan in 2000. In the same year, he joined Bugnion and
since 2010 has been the managing partner of
Bugnion’s Verona office. Marco is also a
member of the board of directors of the firm.
Marco is a European and Italian patent, trade mark and
design attorney. In many years of practice, he has filed
and prosecuted hundreds of cases before EPO, WIPO, EUIPO
and the Italian PTO. He is a recognised technical expert
in patent litigation before the Italian courts. Marco is
interested in IP strategy and has been a lecturer in the
Business Master Intellectual Property Management held by
Bugnion in collaboration with the University of Pisa,
Economics and Management Department. Marco has been
invited to speak at several seminars worldwide, including
Japanese RIETI (Research Institute of Economy, Trade and
Industry) and the New York City Bar Association.