Let’s Make it a Date – Best Method and the Filing Date of the Earliest Complete Application

In the recent decision of NOCO Company v Brown and Watson International Pty Ltd [2025] FCA 887¹, Moshinsky J has provided welcomed clarity around the relevant date by which the best method known to the applicant is to be identified for divisional patent applications. Namely, the relevant date is the date from which the term of the patent is calculated. This means that for divisional patent applications, it is the filing date of the earliest complete or PCT application, not the individual filing date of each divisional application. And thus, it is at the time of filing the PCT application that the best method known to the applicant needs to be included in the specification.

Background

The best method requirement provides that a complete specification must disclose the best method known to the applicant of performing the invention.² It is a powerful ground of revocation as failure to disclose the best method can invalidate the whole patent, making it a ground frequently pleaded by the alleged infringer.

This case involved three patents for car battery jump starters. NOCO was the patentee and the three patents were from the same family, each claiming an earliest priority date of 3 July 2014 based on the filing date of a PCT application. The filing dates of the patents were much later, being in 2020, 2021 and 2022. NOCO brought infringement proceedings against Brown & Watson International Pty Ltd (B&W) and B&W cross-claimed for invalidity. One of the invalidity grounds asserted was that of best method.

Best Method and the Relevant Date

On the question of best method, the key issue was what date is the relevant date at which the best method known to the patentee (NOCO) is to be assessed.³ The options were either:

• The filing date the PCT application (3 July 2014) (NOCO’s position); or
• The filing date of each of the divisional patents (B&W’s position),

with Moshinsky J holding that NOCO’s position is to be preferred.

NOCO’s position was that the knowledge requirement for best method should be assessed at the filing date of the PCT, which “is the first filed application in the claim of divisional applications and the date from which the term of each patent runs“.⁴ NOCO relied on previous decisions of the Federal Court and Full Federal Court to support this decision, which Moshinsky J adopted⁵ and held the relevant date for the knowledge element of best method is that date of filing the PCT application (3 July 2014).

While NOCO submitted that the approach of the Court in Dometic Australia Pty Ltd v Houghton Leisure Products Pty Ltd was “plainly wrong”,⁶ his Honour considered it was not necessary for him to form a view on this point.

Footnotes:

¹ https://www.austlii.edu.au/cgi-bin/viewdoc/au/cases/cth/FCA/2025/887.html

² s 40(2)(a) Patents Act 1990 (Cth).

³ NOCO Company v Brown and Watson International Pty Ltd [2025] FCA 887 at [369]-[398].

⁴ Ibid at [375].

⁵ Pfizer Overseas Pharmaceuticals v Eli Lilly & Co [2005] FCAFC 224.

⁶ NOCO Company v Brown and Watson International Pty Ltd [2025] FCA 887 at [375].