Important update on Australia's flip-flopping "best method" requirement for divisional patent applications

 Not only does Australia retain an archaic "best method" requirement for patents (IPKat), but the Full Court has confirmed that for divisional applications the best method is to be assessed at the time of filing the divisional application (not the parent application). The ongoing "flip-flopping" of the courts on this issue in recent years is taking its toll on applicants and patentees (not to mention their patent attorneys), and fundamentally remains out of step with other major jurisdictions. In particular, the Full Court's decision in The NOCO Company v Brown and Watson International Pty Ltd [2026] FCAFC 44 (NOCO FCAFC) places a very heavy burden on divisional applicants / patentees.

Brief background

Australia is one of the few jurisdictions to retain a “best method” requirement for patent specifications. Under s 40(2)(aa) of the Patents Act 1990 (Cth) (Act), a complete specification must "disclose the best method known to the applicant of performing the invention". Relevantly, this section does not specify the date at which the best method must be disclosed, other than to specify that it must be disclosed in a "complete specification" (typically the specification filed with a PCT or non-provisional application). While it was long thought that "Knowledge Element" for divisional applications is to be assessed at its effective filing date derived from their ultimate parent application, the courts have turned that conventional wisdom on its head in recent years.

First instance flip-flop

"Say what now!?" Kat

The issue first arose in Dometic Australia Pty Ltd v Houghton Leisure Products Pty Ltd [2018] FCA 1573, in which a single judge of the Federal Court determined that the "Knowledge Element" for divisional applications is to be assessed at the date of filing the complete specification for the divisional application (not the parent application). Essentially, the Court reasoned that the case law and statutory language supported the conclusion that the Knowledge Element must be satisfied at the divisional filing date. This decision came as a shock to Trans-Tasman patent attorneys – and even more so to applicants and attorneys in other jurisdictions, who are often unaware that Australia even has best method requirement when drafting their applications.

Therefore, when the Federal issued the first instance decision in The NOCO Company v Brown and Watson International Pty Ltd [2025] FCA 887, waves of relief rippled through the patent attorney profession. While it was not necessary to consider the best method issue to decide the case, the Court nonetheless considered the matter and concluded that the case law not provide any good reason the Knowledge Element for divisional applications should not be assessed as at the filing date of the ultimate parent application.

Appeal flip

In NOCO FCAFC, a three judge bench of the Full Court first examined the statutory language. In this regard, the Full Court considered that the primary judge had conflated the provision in the Act for a PCT specification to be treated as a "complete specification" for certain procedural purposes (s 29A(2)) with the "complete specification" that is to be assessed for revocation purposes (s 138(3)). The Full Court also considered that reference to "the best method known to the applicant" in s 40(2)(aa) means the applicant of the divisional application and not the applicant of the parent application.

The Full Court then went on to consider the relevant case law. In each of these cases, it was agreed that the relevant date for assessing the Knowledge Element was the complete specification filing date, as opposed to the publication date, grant date or priority date (see Rescare Ltd v Anaesthetic Supplies Pty Ltd [1992] FCA 811; Pfizer Overseas Pharmaceuticals v Eli Lilly & Co [2005] FCAFC 224; C Van Der Lely NV v Ruston’s Engineering Co Ltd [1993] RPC 45, Les Laboratoires Servier v Apotex Pty Ltd [2016] FCAFC 27). Notably, none of these cases expressly considered divisional applications when determining the date for assessing the Knowledge Element.

On the basis of these cases and the statutory language, the Full Court found that the Knowledge Element must be satisfied at the filing date of the divisional application. Interestingly, the Full Court declined to take into account any policy considerations set forth by the parties.

Appeal flop?

Not only does the NOCO FCAFC decision create an undue burden on divisional patent applicants, but the Full Court's reasoning also does not appear to be overly sound and creates a misalignment between the date for assessing sufficiency and support, and the best method. Relevantly, none of the cases referenced by the Full Court (other than the single judge decisions in Dometic and NOCO) concerned divisional applications, nor does the language of the Act unequivocally support the Full Court's construction.

Additionally, unlike the judge at first instance in NOCO, neither the Court in Dometic nor the Full Court in NOCO FCAFC had any regard to an earlier Full Court decision, in which the phrase “the filing date of the complete application” in relation to a divisional application was construed as being the filing date of the parent application (Mont Adventure Equipment Pty Ltd v Phoenix Leisure Group Pty Ltd [2009] FCAFC 84). In particular, Emmett J helpfully stated at [14]:

The phrase "the filing date of the complete application" must be construed in the context of all of the provisions of the 1990 Act and the Regulations, so as to give a harmonious result achieving the apparent goal of the provisions. To construe the phrase as referring to the Parent Application and not to the Divisional Application achieves that result. The construction is reasonably open and is consistent with the structure of the 1990 Act and the Regulations as a whole, particularly in relation to the treatment of divisional applications and avoids anomalous or unreasonable results.

This appears to reflect a much more pragmatic approach to assessing all internal disclosure requirements for divisional applications (such as sufficiency, support, best method and clarity) than applying different dates to different requirements.

Takeaways

The implications of this decision are significant, because it means that if divisional applications are not supplemented at the time of filing with any better method known to the applicant between the time of filing the parent and divisional applications, the patent may be vulnerable to invalidation. This could even include methods developed by third parties, if it can be established that they were known to the applicant the time the divisional application was filed.

There is no appeal as of right against this decision. However, the parties may request Special Leave to appeal the decision to the High Court of Australia within 28 days of the decision. Stay tuned for updates in relation to any potential appeal.