The Doctrine of Equivalents – where are we now?
2023 update

Since the Supreme Court judgment in Actavis v Eli Lilly [2017] UKSC 48, the UK has had a doctrine of equivalents as part of its law on patent infringement.  In this updated article, we look at the impact that this doctrine has had on our courts and the cases before them, taking into account judgments handed down in 2022. In a world where everyone loves data and statistics, we have distilled the increasing wealth of UK case law on this doctrine into a few easy-to-digest graphs.

To conduct this analysis, we have reviewed the patent infringement judgments handed down each year from 2017 (post-Actavis, which was handed down in July 2017) to the end of 2022 (which we have called “Infringement Judgments”) and identified in which of those judgments infringement under the doctrine of equivalents was in issue (which we have called “DoE Judgments”).[1]

In this article, we analyse:

  • the number and proportion of patent infringement judgments in which an argument of infringement by equivalence has been advanced at trial;
  • the number of judgments in which infringement by equivalence was found;
  • the areas of technology involved in those judgments; and
  • how often patent prosecution history has been relied on to try and avoid a finding of infringement by equivalence.

We identified 4 DoE Judgments handed down in 2022,[2] which we have included in our analysis. We comment further on 2 of these decisions below.


The test for equivalence

By way of reminder, the three questions set out in Actavis to determine infringement under the doctrine of equivalents were as follows: 

“i) Notwithstanding that it is not within the literal meaning of the relevant claim(s) of the patent, does the variant achieve substantially the same result in substantially the same way as the invention, ie the inventive concept revealed by the patent?

 ii) Would it be obvious to the person skilled in the art, reading the patent at the priority date, but knowing that the variant achieves substantially the same result as the invention, that it does so in substantially the same way as the invention?

iii) Would such a reader of the patent have concluded that the patentee nonetheless intended that strict compliance with the literal meaning of the relevant claim(s) of the patent was an essential requirement of the invention?”

The Supreme Court clarified that, in order to establish infringement under the doctrine of equivalents, the answer to the first two questions would have to be “yes”, and the answer to the third question would need to be “no”.


Proportion of Infringement Judgments arguing the DoE

Between 2018 and 2020, the percentage of DoE Judgments as a proportion of the total Infringement Judgments increased year-on-year, as shown in Figure 1 below, reaching a peak of 90% in 2020.  However, there was a dip to 37% in 2021, and similarly only 40% of the 2022 Infringement Judgments relied on an argument under the doctrine of equivalents.

These data are also represented in Figure 2, which shows the number of DoE Judgments in pink, and the number of Infringement Judgments in which the doctrine of equivalents was not raised in blue.


Figure 1: Chart showing the number of DoE Judgments as a percentage of Infringement Judgments, by year,
from 14/07/2017 – 31/12/2022


Figure 2: Chart showing the number of DoE Judgments (shown in pink), compared to the total number of Infringement Judgments (shown in pink and blue) per year, from 14/07/2017 – 31/12/2022


DoE Judgments where infringement by equivalence has been successfully argued

Since 2019, where infringement by equivalence was found in all of the 7 DoE Judgments (i.e. a success rate of 100%), the success rate has been decreasing.  In 2021, arguments raised under the doctrine of equivalents had a success rate of 43% and, following our review of the 2022 DoE Judgments, this success rate has continued to fall. In 2022, for the first year since our analysis began, the doctrine of equivalents was not successfully argued in any cases in which it was run.

The year-on-year trends can be seen in Figure 3 below, which shows the number of DoE Judgments per year (the height of the whole bar), and the number of these cases in which infringement by equivalence was actually found (the pink portion of each bar).

Taking all of the post-Actavis DoE Judgments to date, the doctrine has been successfully argued in 16 out of 30 cases, giving an overall success rate of 53%.  However, as will be explored further below, in many of the cases where infringement by equivalence was found, the case did not turn on this point (either because infringement under a normal claim interpretation was also found, or because the patent was held to be invalid).


Figure 3: Chart showing the number of DoE Judgments and the number of cases in which a finding of infringement under the DoE was found, from 14/07/2017 – 31/12/2022.


DoE Judgments turning on a finding of equivalence

As noted above, no finding of infringement by equivalence was made in any of the 4 2022 DoE Judgments and in only 1 of these cases was the patent found valid.[3]

Taking into consideration all DoE Judgments handed down from 2017 to 2022, only 20% of DoE Judgments have actually turned on a finding of infringement by equivalence, as shown in Figure 4 below.  This may be a contributing factor to the apparent recent decline in popularity of the argument.


Figure 4: Chart showing the number of DoE Judgments which have turned on a finding of equivalence,
from 14/07/2017 – 31/12/2022


Areas of technology where infringement by equivalence has been argued

The following chart shows the different areas in which infringement by equivalence has been argued to date (as identified from the IPC classes of the patents in dispute).

While pharmaceutical and chemical patents in the life sciences sector continue to dominate, the UK courts have seen cases covering technologies including construction, engineering and electronics. Two recent additions are actions covering H02 (Generation, Conversion or Distribution of Electric Power) and A45 (Hand or Travelling Articles).


Figure 5: Chart showing the distribution of IPC codes in the DoE Judgments so far (up to 31/12/2022)


Prosecution history

In Actavis, the Supreme Court commented on the relevance of the patent prosecution history in the assessment of claim scope. As a reminder, the UK courts have typically discouraged looking at the contents of prosecution files for the purposes of determining claim scope and have rarely done so.  Lord Neuberger clarified in Actavis that the two situations where it would be appropriate to do so are:

  1. if the point at issue is unclear based on the specification, and the file unambiguously resolves the point; or
  2. if it would be contrary to the public interest to ignore the file, e.g. where a patentee has stated previously that it would not enforce the patent against a particular variant.

Figure 6: Chart showing the number of DoE Judgments where prosecution history has been argued so far (14/07/2017 to 31/12/2022).


Figure 6 above shows that defendants have attempted to rely on the prosecution history in only a minority of DoE Judgments – only 7 of the 30 DoE Judgments since Actavis have discussed prosecution history. Notably, in none of those cases has prosecution history been successfully relied on to defend an infringement by equivalence claim.

In 2022, we identified only one DoE Judgment in which the patent prosecution history was raised as a defence.[4]  However, given that the equivalence argument failed on the third limb of the Actavis question, as discussed below, the arguments based on the file wrapper were not considered by Mr Justice Meade.


Recent case law on the doctrine of equivalents

Disclosed but not claimed is disclaimed

In our last update, we referred to a principle of German law,[5] which states that, where embodiments of an invention are disclosed but not subsequently claimed, they should not be considered to be encompassed by the claims, on either a literal or equivalence basis.  A similar line of thinking has been taken in some of the UK case law, particularly in relation to the third (“strict compliance”) limb of the Actavis test (as set out in full above).

In Shenzhen Carku Technology v The NOCO Company,[6] Mr Justice Meade noted that both embodiments (two types of switches, known as “relays” and “power FET switches”) were mentioned in the specification, but only a power FET switch was claimed.  Meade J considered that this gave “some support to the view that relays were deliberately not claimed”.  Although relays were mentioned in the specification only in relation to the prior art and not the invention,[7] Meade J still held this to be a relevant consideration, as the skilled person may appreciate that it “would be rational for the patentee to distance the claims from the acknowledged prior art”.

Meade J referred to, and agreed with, an earlier judgment of Birss LJ,[8] in which he commented that if the two alternatives are not materially different, such that question 1 is answered in the affirmative, this “may make it all the more significant that the patentee, knowing both of them, only mentioned one of them in the claim”. It was not relevant that the skilled person would consider relays and power FET switches as interchangeable at the priority date, and both would be within the CGK of the skilled person.

Meade J concluded that relays were not within the scope of the claim under the doctrine of equivalents, on the basis of Actavis question 3.  Another factor contributing to this finding was the use of broader, functional language in other parts of the claim and the description (e.g. the use of the much more general term, “switch”), but the use of narrower, specific language in the claim relating to the physical detail of the switch (i.e. “a power FET switch”).


Introduction of a UK Formstein defence

In our last update, we noted that Birss LJ considered, obiter, in Facebook v Voxer[9] that where a claim is found to be infringed under the doctrine of equivalents but, as a result would be invalid for lack of novelty or obviousness, the claim should be held to be valid, but not infringed by the variant.  Given that Birss LJ did not have to resolve the issue, this commentary was not binding.

In the recent IPEC case, Vernacare v Moulded Fibre Products,[10] the patentee argued that the scope of the claim should be extended under the doctrine of equivalents, to cover a variant that was found to be part of the common general knowledge.  Deputy High Court Judge Nicholas Caddick QC, referring to Birss LJ’s judgment, found that there was no infringement under the doctrine of equivalents, due to the operation of a Formstein defence.  This case is therefore significant, being the first case in the UK courts where a Formstein defence was successfully relied upon to avoid a finding of infringement under the doctrine of equivalents.  Interestingly, the judge considered that, in the alternative, the equivalence claim would fail under the third limb of the Actavis test, as “the skilled person would have concluded that the patentee did intend a strict compliance with the literal (i.e. normal, purposive) meaning of claim 1, because the claim would otherwise be invalid for obviousness”.


EPO Guidelines

In our last article, we highlighted the introduction of the 9th edition of the EPO guidelines in March 2021 which stated that, in order to meet the requirement of Art. 84 EPC, embodiments in the description that are not covered by the claims must be deleted, unless it is “prominently stated” that the embodiment is not “covered by the claims”.  We noted that such statements may pose problems for patentees who later want to rely on the doctrine of equivalents in the UK, particularly in relation to the third limb of the Actavis test, as they may suggest that the patentee did intend strict compliance with the literal meaning of the relevant claims.  However, there have been two key developments at the EPO since.

Firstly, the Guidelines have been revised twice, in March 2022 and March 2023, and in both editions, the EPO softened the requirements surrounding embodiments which are not covered by the claims. For instance, the current version permits such embodiments to be marked as “not encompassed by the wording of the claims” (our emphasis), which could be useful when arguing equivalents – as this wording arguably makes less of a concession than stating that an embodiment is not “covered by the claims”. The current Guidelines also describe more circumstances where embodiments can be retained.

Secondly, a Board of Appeal decision has called into question the requirement to amend the description at all. In particular, decision T 1989/18 of 16th December 2021 sent shockwaves around the patent attorney community by holding that Art. 84 EPC (historically the legal basis for description amendments) could not be used as the legal basis for refusal to grant the patent, where “irrelevant or unnecessary” matter had been retained, and there was no other legal basis to do so.  However, despite the initial interest in decision T 1989/18, it is now considered to be relatively isolated, and has not been followed in more recent decisions. T 1989/18 was cited in the 10th edition of the EPO’s case law manual (the ‘Case Law of the Boards of Appeal’), which would normally give a decision a certain gravitas, but four decisions which do not follow T 1989/18 are cited in the same chapter.

To summarise, in practice, the EPO is still requiring patent attorneys to amend the description and to make statements regarding embodiments which do not fall within the wording of the claims, in line with the Guidelines, which are closely followed at Examining Division and Opposition Division levels. However, patentees and applicants concerned of hindering potential equivalence arguments in the future now have more options to push back than they had in 2021: they can push to retain more embodiments, and to make more nuanced accompanying statements. They may even try pushing back against the requirement at all, although this is unlikely to be successful below appeal level.



Following our review of the recent UK judgments in which a doctrine of equivalents argument was advanced, we have identified some key themes:

  • The number and proportion of DoE Judgments has decreased over the past two years and is also becoming less successful, with 2022 being the first year in which infringement under the doctrine of equivalents was not found in any case running this argument;
  • The doctrine of equivalents is being pleaded in patent infringement cases covering a broad and expanding range of areas of technology. The life sciences field continues to dominate but the doctrine has now been applied to more diverse areas, such as “electric power” and “hand or travelling articles”.
  • While parties in 7 DoE Judgments post-Actavishave sought to rely on the patent prosecution history, we have identified no instances where the prosecution history was successfully used to defend an infringement claim.



[1] All information has been obtained from publicly available judgments and not from an analysis of the pleadings. We have included cases from the IPEC, Patents Court, Court of Appeal and the Supreme Court. For completeness, we note that in calculating the number of Infringement Judgments, we have only included final judgments (i.e. not interim decisions), and only those judgments in which infringement was in issue.  We have not included cases where infringement was admitted (and therefore where it is unclear from the judgment on what basis infringement was argued). Where a case has been appealed, we have included both the first instance and appeal decisions in the statistics, but only where infringement was also in issue on appeal.  When calculating the number of DoE Judgments, we have included all cases where a party is said to have run an argument under the doctrine, even if this was not considered by the Judge (e.g. because the patent was held to be invalid).

[2] Advanced Bionics AG v Med-El Elektromedizinische Gerate [2022] EWHC 1345 (Pat); Vernacare Ltd v Moulded Fibre Products Ltd [2022] EWHC 2197 (IPEC); Shenzhen Carku Technology Co Ltd v Noco Co [2022] EWHC 2034 (Pat); and Teva Pharmaceutical Industries Ltd v Novartis AG [2022] EWHC 2847 (Pat).  For completeness, we note that we identified a further case, J. C. Bamford Excavators Limited v Manitou [2022] EWHC 1724, in which the doctrine of equivalents appears to have been relied on.  However, the discussion on infringement is largely set out in a confidential annex to the judgment and hence it is not clear whether infringement was found under a normal construction, or under the doctrine of equivalents.  For this reason, we have excluded this judgment from our analysis.

[3] Vernacare v Moulded Fibre Products [2022] EWHC 2197 (IPEC)

[4] [2022] EWHC 2034 (Pat).  This case has been appealed, and the appeal is due to be heard in December 2023.

[5] This principle arose from Case X ZR 16/09 – Okklusionsvorrichtung (Occlusion Device)

[6] [2022] EWHC 2034 (Pat)

[7] Meade J distinguished these facts from his earlier judgment, of Optis v Apple [2021] EWHC 1739 (Pat), in which the two options were mentioned as alternatives in relation to the general teaching of the invention.

[8] Facebook v Voxer [2021] EWHC 1377 (Pat)

[9] [2021] EWHC 1377

[10] [2022] EWHC 2197 (IPEC).  This case has been appealed and the appeal is due to be heard in June 2023.