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Full Federal Court of Australia Clarifies the Relevant Date for assessing Best Method in Patent Applications

The Full Court in The NOCO Company v Brown and Watson International Pty Ltd [2026] FCAFC 44 (the NOCO decision) has upheld an appeal of the first instance decision of Justice Moshinsky (discussed in our earlier article here). Notably, the Full Court has held that the relevant date for assessing best method is the filing date of the divisional complete specification itself, not the filing date of the parent or original PCT application. 

The decision has significant implications for portfolio management and divisional filing strategies.

Best Method requirement

Unlike most countries, Australia retains a requirement to disclose the ‘best method’. Section 40(2)(aa) of the Patents Act 1990 requires that a complete specification:

“disclose the best method known to the applicant of performing the invention”.

Failure to describe the best method known to the applicant in the specification can result in the entire patent being found invalid. Usually this involves an opponent or applicant for revocation showing that the applicant was aware of a better method of performing the invention but did not disclose it in the specification. It has become a commonly raised ground of invalidity in patent proceedings and has been successfully used to invalidate a patent. 

When assessing if there is a better method, and whether it was known to the applicant, the date of the assessment is crucial. 

When is the best method assessed

The Patents in suit in the NOCO decision were standard patents filed as divisionals, tracing back to a PCT application filed in 2014. These divisional applications were filed much later, between 2020 and 2022.

After filing of the PCT application, but before the filing of the divisional applications, various limitations of the product disclosed in that application were discovered and overcome. 

The Full Court agreed with the primary judge’s factual findings that:

• the changes to overcome the limitations represented the best method of performing the invention, and
• NOCO was aware of them well before filing the divisional applications.

Because those improvements were not disclosed in the divisional specifications, all relevant claims failed s 40(2)(aa) and were invalid on that ground alone.

The dispute was whether the “best method known to the applicant” should be tested at:

• the PCT filing date (as the primary judge held), or
• the divisional filing date (as ultimately accepted by the Full Court).

The Full Court’s Reasoning

The Full Court disagreed with the primary judge and reversed this aspect of the decision.

The Court emphasised that s 40(2)(aa) looks to the specification of the patent under attack, not to an ancestor specification. Thus, the relevant specification is the divisional specification, not the PCT specification.

Moreover, the phrase “best method known to the applicant” was critical. The Court considered that the “applicant” is the entity filing the divisional application, not the historic PCT applicant. The applicant for a divisional may be different (e.g. by assignment). At the time of filing the divisional, the applicant may know more—and often does know more—about how best to perform the invention.

The Court considered that testing best method at the earlier PCT date would, in effect, allow applicants to freeze disclosure at an earlier level of knowledge while claiming a later-defined monopoly.

Key Takeaways

Best Method should be re‑assessed for each divisional

Each divisional application resets the best‑method clock. The best method of performing the invention known to the applicant at the divisional filing date must be included in the description. This requires consideration of both who the applicant is (they may be different from earlier applications) and what their knowledge is.

Commercial embodiments matter here. Improvements adopted to solve reliability, efficiency, or performance problems with the originally disclosed invention may represent a ‘better method’ of performing the invention and should be included in the divisional application on filing. This includes improvements made by competitors, known to the applicant.

It is worth noting that while subject matter can be added to the divisional application, a claim which is directed to that subject matter is unlikely to be entitled to any priority date earlier than the filing of the divisional application. As a result, such claims may be vulnerable to invalidity in light of publications and use in the intervening period. In such cases, amendment of a parent patent to add a dependent claim, or an application for a patent of addition may be worth considering in conjunction with the intended divisional application.

Other strategies for portfolio management

Various strategies for managing a portfolio may be available. A best method issue is unlikely to be raised during examination, but it is increasingly an aspect of litigation. 

One possible strategy, for key patent families is to keep a divisional application pending. If litigation arises with the possibility of a best method issue arising, it will then be possible to file a new divisional application and add any “best method” previously omitted. 

Other strategies may be available and each case must be assessed on its own facts in light of commercial context.  It is highly recommended that if you are concerned that the best method is not disclosed, you discuss the matter with your Australian patent attorney. Please contact us if you need our help.

Future developments

The NOCO decision was not appealed to the High Court of Australia, thus it is the last word on this matter for now. However, various organisations have suggested that the best method requirement as a whole is out of step with the rest of the world and are lobbying for its repeal. 

We will keep you updated as to any developments in this space.

David Nowak - June 2026