Summary
The Full Federal Court’s decision in The NOCO Company v Brown and Watson International Pty Ltd [2026] FCAFC 441 sharpens the practical bite of Australia’s “Best Method” requirement for divisional patents. By reversing the first‑instance approach and confirming a “filing‑date‑focused test” for divisional applications, the Court has reinforced a stricter compliance standard that will influence how patent families are drafted, prosecuted and attacked in litigation.
Put simply, the case turns on timing: for a divisional application, is “Best Method” judged by what the applicant knew when the parent was filed, or by what it knew when the divisional itself was filed? The Full Court’s answer – each divisional stands on its own filing date – creates real tension with the rule that divisional applications cannot add new matter beyond what the parent already discloses.
Background: What “Best Method” Demands
Australian patent law requires more than a specification that merely enables an invention to be performed. Section 40(2)(aa) of the Patents Act 19902 requires the complete specification to disclose “the best method known to the applicant of performing the invention”. The policy is straightforward: the patentee receives a time‑limited monopoly, and in return must give the public full and frank disclosure of the most effective way the applicant knows to put the invention into practice.
In practice, “Best Method” is not satisfied by describing any workable embodiment. If the applicant knows a preferred embodiment, process parameter, refinement or implementation detail that materially improves performance, that preference must be disclosed with enough detail for a skilled person to carry it out. The inquiry is factual and turns on what the applicant actually knew at the relevant time. Non‑compliance can be fatal: a failure to disclose the best method can be a ground revocation even where the invention is otherwise enabled, typically pleaded via s 138(3) of the Patents Act 19903.
Why the Requirement Can Still Help Applicants
Although it is often treated as a trap for the unwary, “Best Method” can also improve patent quality. A specification that squarely discloses the preferred implementation tends to be clearer, more defensible and better aligned with the commercial product. It can also reduce “design‑around” opportunities by putting key refinements into the public disclosure, rather than leaving them to be inferred or reverse‑engineered.
The downside in Australia is that this lack of disclosure is not something an applicant can safely fix later: if the best method known at filing is not in the complete specification, subsequent amendment may be constrained (and, in the case of divisional applications, effectively blocked) by added‑matter rules.
The Divisional Problem: Timing and Parent Support
Divisional applications sit at the centre of the NOCO dispute because they are filed later in time but must stay within the confines of the disclosure in the parent.
A divisional cannot introduce new matter. Yet the “Best Method” obligation asks what the applicant knew about the best way to perform the invention at the relevant filing date. If the relevant date is the filing date of the divisional application (rather than the filing date of the parent), an applicant who has developed a superior way of working the invention after the parent filing may be obliged to disclose it – but unable to do so if the parent specification does not support that improved method. A further practical wrinkle is that the inquiry is directed to what the applicant who files the divisional knew at that time, which can matter where ownership has changed within a patent family.
At first instance4, the Court effectively anchored the inquiry to the parent (or PCT) filing date, meaning later improvements did not need to appear in a later‑filed divisional. On appeal, however, the Full Court rejected that approach and treated each divisional as a separate application that must meet the statutory standard by reference to its own filing date. That shift is what creates a practical “trap”: compliance can depend on whether the parent was drafted broadly enough to accommodate improvements identified down the track.
For practitioners, the message is to treat “Best Method” as an active drafting issue, not a box‑ticking exercise: the specification should identify the preferred way of working the invention (as known at filing) and explain it with enough practical detail that the skilled reader can reproduce it.
How Unusual is Australia?
Australia is comparatively unusual in maintaining a best‑method obligation that can invalidate a granted patent. Some jurisdictions have no equivalent requirement, and others treat it as non‑fatal. That context matters: the Full Court’s approach reinforces a disclosure standard that is already stricter than many major patent systems, increasing the premium on careful drafting for applicants seeking Australian protection.
Internationally, approaches differ. The United States retains a “Best Mode” requirement in application drafting, but failure is no longer a ground of invalidity. Many other major systems focus on enabling disclosure without a separate, enforceable “Best Method” inquiry. Against that backdrop, NOCO reinforces that Australia remains a comparatively demanding jurisdiction on this point.
What the Full Court Decided
The Full Court held that compliance with the “Best Method” requirement is assessed by reference to the filing date of the complete specification for the patent in suit – including where that patent is a divisional application. In other words, the applicant’s relevant knowledge is what it knew at the time it filed that divisional complete specification, not what it knew at the parent’s earlier filing date.
Thus, each divisional is a separate application with its own filing date, and the statute requires each complete specification to comply in its own right. The Full Court therefore rejected the idea that the parent’s filing date could “freeze” the applicant’s best‑method knowledge for later‑filed divisional applications.
Practical Consequences for Patent Owners and Challengers
Following the Full Court’s decision, validity risk increases for some existing divisional patents – particularly those filed years after the parent, where the patentee’s development work continued and a superior method may have been known by the time the divisional was filed. Defendants in infringement disputes are likely to treat “Best Method” as a sharper revocation ground, including by seeking discovery and evidence about post‑priority R&D and what the applicant knew when each divisional was filed.
For applicants, the most difficult feature is the structural squeeze between two rules: (a) a later‑filed divisional must disclose the best method known at its own filing date, but (b) it cannot add new matter beyond what the parent supports. The likely response is behavioural: more careful (and often more expansive) parent drafting, earlier or more frequent divisional applications where commercially justified, and proactive portfolio reviews to identify families where post‑filing improvements might create a best‑method vulnerability.
Bottom Line
The Full Court’s decision re‑energises “Best Method” as a live issue in Australian patent drafting and disputes. For divisional strategies, it underscores a simple but demanding proposition: each complete specification must stand on its own, assessed at its own filing date, and applicants should assume the court will ask whether the document really discloses the preferred way the invention was known to work at that time. The practical response is to carefully draft ‘parent’ applications with enough depth to support future divisional applications, and to manage patent families with the same discipline applied to ongoing product development.
Takeaway
For Australian filings, the message is plain: assume “Best Method” will be tested, and draft (and sequence) parent and divisional specifications with that scrutiny in mind.
- The NOCO Company v Brown and Watson International Pty Ltd [2026] FCAFC 44 (10 April 2026) ↩︎
- PATENTS ACT 1990 – SECT 40 Specifications ↩︎
- PATENTS ACT 1990 No. 83, 1990 – SECT 138 Revocation of patents in other circumstances ↩︎
- The NOCO Company v Brown and Watson International Pty Ltd [2025] FCA 887 (7 August 2025) ↩︎
