When filing patent applications in Australia and New Zealand, a patent specification must disclose the best method of performing the invention known to the applicant. This forms part of the “patent bargain” where, in exchange for patent protection, the inventor must make the knowledge required to produce and use their invention available to the public.
The “best method” requirement applies to all claim types. For example, the specification must disclose the best way of performing a claimed method, and the best version of a product falling within the scope of a product claim.
Australia
Disclosure requirements
Australia’s Patents Act 1990 s 40(2)(aa) states that a complete specification must disclose the best method known to the applicant of performing the invention.
The “invention” referred to is the embodiment which is described in the specification and around which the claims are drawn.[1]
Exactly what the disclosure requires will depend on the nature of the invention. In general, where the claims encompass a number of different embodiments, combinations of features, or numerical ranges, the specification should disclose the specific embodiment, combination, or values that best achieves the advantages the invention provides.[2]
However, the best method does not have to be specifically identified or labelled as such. If more than one method of performing the invention is described, it is not necessary to point out which method is better or preferred, or why.
Best method known at what date?
Applicants often continue to develop their technology after filing an initial patent application, and may produce further improvements to the invention. The specification must disclose the best method known to the applicant, but at what date is this assessed? There have been some recent developments in this regard, particularly for divisional applications.
In a 2018 decision (‘Dometic’),[3] the Federal Court of Australia determined that the relevant date for determining the best method known to the applicant is the filing date of the application.
For divisional applications, Dometic determined that the relevant date is the filing date of the divisional application, rather than the filing date of the ultimate parent application (the effective filing date). This means that an applicant who had continued to develop a technology after their initial filing, discovering new and improved methods of carrying out the invention, and who wanted to file a divisional application, would have to disclose their new and improved method in the divisional or fail to meet the best method requirement.
This position was contradicted in a 2025 decision of the Federal Court of Australia (‘NOCO’).[4] In NOCO, the Court found that the relevant date for determining the best method known to the applicant is the filing date from which the patent term is calculated. For a divisional application, this would be the effective filing date.
NOCO was appealed to the Full Federal Court[5] which, contrary to the primary judge’s finding, agreed with Dometic that the relevant date is the filing date of the divisional application.[6]
Therefore, the position in Australia is that a divisional application must disclose the best method known to the applicant at the date the divisional is filed. IP Australia’s patent examination manual has been updated to reflect this.
Potential consequences of failing to disclose the best method
Failure to disclose the best method is a ground for pre-grant opposition or revocation of a patent.
The best method must be disclosed in the specification at its filing date.[7]This means there is no amendment that can cure a best method deficiency — if the patent or application did not include the best method at its filing date, it is invalid.
For this reason, attacks based on the best method requirement have proven an effective strategy during opposition and revocation proceedings.
When filing a divisional application in Australia, applicants should carefully consider whether the best method has changed since the original filing, and weigh up the risks of failing to disclose an updated best method against publicly disclosing new material that might otherwise be kept as a trade secret or be the subject of a further patent application.
New Zealand
The Patents Act 2013 s 39(1)(b) requires that the complete specification must disclose the best method of performing the invention that is known to the applicant and for which there is an entitlement to claim protection.
As in Australia, failure to disclose the best method is a ground of opposition or revocation.
However, unlike Australia, the filing date of a New Zealand divisional application is usually antedated to be the same as that of the ultimate parent. Therefore, it is likely that the date for determining when the best method is known will be the same for divisional applications and their parent applications, i.e. the original filing date of the ultimate parent application.
[1] Zoetis Services LLC v Boehringer Ingelheim Animal Health USA Inc [2024] FCAFC 145, [14]–[15].
[2] Les Laboratoires Servier v Apotex Pty Ltd [2016] FCAFC 2, [135].
[3] Dometic Australia Pty Ltd v Houghton Leisure Products Pty Ltd [2018] FCA 1573 (‘Dometic’).
[4] The NOCO Company v Brown and Watson International Pty Ltd [2025] FCA 887 (‘NOCO’).
[5] The NOCO Company v Brown and Watson International Pty Ltd [2026] FCAFC 44 (‘NOCO appeal’).
[6] Ibid, [218].
[7] Pfizer Overseas Pharmaceuticals v Eli Lilly & Co [2005] FCAFC 224, [379].
