Full Court confirms Dometic: Best method assessed at filing date of divisional patent applications
What you need to know
- The Full Federal Court in The NOCO Company v Brown and Watson International Pty Ltd [2026] FCAFC 44 has clarified that the date for assessing the best method ground of invalidity is the filing date of the complete specification in suit (which may be the date a divisional patent application was filed).
- In Australia, there is no limit on the number of divisional patent applications that may be filed in a single family, which is each a complete specification.
- The Full Court's decision confirms that each divisional patent application must disclose the best method known to the applicant, at each application's filing date.
- The unanimous decision of Beach, Downes and Jackman JJ considered that this outcome was consistent with the statutory text, earlier Australian authorities and policy (to the extent relevant).
What you need to do
- Patentees should carefully consider their patent portfolios for vulnerability to this ground, which is effectively the position under Dometic Australia Pty Ltd v Houghton Leisure Products Pty Ltd (2018) 135 IPR 403 as it existed prior to the first instance decision in The NOCO Company v Brown and Watson International Pty Ltd [2025] FCA 887.
- If possible, patentees may consider filing further divisionals, to include a compliant disclosure of any later discovered best method.
- Alleged infringers or parties otherwise seeking to revoke patents should consider whether this invalidity ground may assist them, especially in the context of divisional patent applications filed some time after the ultimate parent (grandparent) priority document.
- Discovery and other mechanisms for obtaining copies of relevant patentee documents may take on greater prominence in order to investigate whether better methods of performing the invention had become known.
The NOCO Company v Brown and Watson International Pty Ltd [2026] FCAFC 44
The Australian Patents Act 1990 (Cth) continues to include a best method ground of validity. Specifically, section 40(2)(aa) provides that "[a] complete specification must: … disclose the best method known to the applicant of performing the invention". However, the Act is silent on when that requirement is to be assessed.
In The NOCO Company v Brown and Watson International Pty Ltd [2026] FCAFC 44, a unanimous Full Court (Beach, Downes and Jackman JJ) held that best method is to be assessed at the date of filing the complete specification for the patent in suit: at [218]. This reverses the first instance decision, and may have significant implications for patent attorneys, patentees and alleged infringers.
Ashurst acted for the successful respondent, Brown and Watson International Pty Ltd.
Background to the dispute
The NOCO Company (Noco) is the patentee of a family of Australian patents relating to portable car jump starters. Noco commenced infringement proceedings, alleging that Brown and Watson International Pty Ltd (B&W) infringed numerous claims of three of those patents through the sale of B&W's portable car jump starters.
B&W cross-claimed for revocation and, at first instance, was successful: The NOCO Company v Brown and Watson International Pty Ltd [2025] FCA 887. B&W was successful primarily based on lack of inventive step, and lack of novelty in light of deferred priority date.
B&W had also argued that the divisional patents in suit were invalid for failure to disclose the best method. The trial judge, Justice Moshinsky, found:
- for B&W on the factual issue, that Noco had learned of a better method after filing the ultimate parent; and
- against B&W on the legal issue, that the best method ground failed because the date for assessing best method was the filing date of the ultimate parent (great grandparent patent filed many years earlier) (although this finding was in obiter, given the conclusions on the other grounds).
Noco appealed, and B&W filed a notice of contention to press the best method ground.
The decision on appeal
Noco's appeal was dismissed and the Full Court made various interesting observations on lack of inventive step and priority date. This article focuses on the best method ground raised in B&W's notice of contention.
The dispute between the parties on best method was primarily on the legal issue, whether the patent must disclose the best method known to the applicant at:
- the filing date of the ultimate parent patent, in this case the priority document PCT 434, filed in 2014 (Noco's position); or
- the filing date of each patent in suit, in this case the filing dates of each divisional patent, filed between 2020 and 2022 (B&W's position).
The Full Court held that B&W's position was preferred, based on the statutory language, previous Australian cases, and policy reasons.
In relation to the statutory language, the Full Court observed that s 40(2)(aa) refers to "a complete specification", which is defined in the Act as a specification filed in relation to a complete patent application. The Act also makes clear in section 79B that divisional patent applications are separate complete applications, and therefore specifications, from their ultimate parent. As a result, the Full Court held that the statutory language of s 40(2) draws attention to whether the complete specification in suit complies with the internal validity requirements, and said one could not treat the filing date of the ultimate parent as the filing date of the patents in suit: at [206]-[207].
In relation to the Court's previous cases that considered best method and filing date, the Full Court stepped through each of the decisions, and concluded that B&W's position was consistent with those earlier cases: at [210]. In particular, the Full Court rejected Noco's reliance on a single sentence in Rescare Ltd v Anaesthetic Supplies Pty Ltd (1992) 25 IPR 119 which suggested that the relevant date is the date from which the monopoly commences: at [211]-[212]. The Full Court noted among other things that there was no authority or commentary cited in support for that apparent proposition. We also note that a divisional patent does not provide an enforceable monopoly from its patent date in any event: see s 57.
As a result, the Full Court reached its key conclusion at [218]: "the language of the relevant statutory provisions and the previous decisions of this Court support the conclusion that the relevant date for ascertaining the patentee’s knowledge of the best method is the date of filing the complete specification for the patent in suit, not the earlier date of a PCT specification".
The Full Court observed that both parties had advanced policy arguments in favour of their positions, and that these were largely irrelevant given the statutory language and precedent discussed above. However, the Full Court did observe that there was force in B&W's policy arguments in favour of the later date for assessing the patentee's knowledge: at [219]-[223].
Implications and next steps
The effect of the Full Court's decision is that Justice White's 2018 decision of Dometic Australia Pty Ltd v Houghton Leisure Products Pty Ltd (2018) 135 IPR 403 remains the law. Divisional patent applications must disclose the best method known to the applicant at the time they are filed. The Full Court also noted that divisional patent applications can include added matter (unlike, for example, amendments governed by s 102(1)): at [220].
This decision has significant consequences for patent "thickets", or large families of patents comprising many divisionals. Alleged infringers should seriously consider best method as a revocation ground if such divisional patents are asserted against them. This remains subject to the usual difficulties in obtaining access to documents that might reveal the patent applicant's state of mind at the relevant date(s).
Patentees should carefully consider whether any of their patent portfolios are vulnerable to this ground. If so, and if it is still possible to file further divisionals, patentees should consider doing so. However, there is a tension, as introducing a further disclosure in a divisional may tip-off potential revokers to the vulnerability.
Other authors: Caitlin Kalaja, lawyer.
