Navigating Australian Divisional Patent Applications: Requirements, Challenges, and Recent Developments

The filing of divisional applications in Australia requires careful navigation of strict time limits and evolving case management procedures that have fundamentally changed the strategic landscape for applicants. Australia's divisional application system presents both flexibility and complexity, demanding a thorough understanding of both established requirements and procedural developments.

Filing Requirements and Time Limits

Basic Requirements for Divisional Status

Filing a divisional application in Australia requires compliance with several fundamental requirements that must be satisfied to claim divisional status. The applicant must be the same as that of the parent applicant. Additionally, the patent request must specifically invoke sections 79B or 79C of the Australian Patent Act 1990 (the Act) and state the parent application number.

Under certain circumstances, an application can be converted to a divisional of another application by amendment of the patent request.

Critical Time Constraints

The timing requirements for divisional applications represent one of the most crucial aspects of Australian practice. Under section 79B of the Act, divisionals of standard (i.e., 20-year) patent applications may be filed at any time while the parent application is pending and, if accepted (i.e., allowed), within three months of the date of advertisement of acceptance. The divisional application may be for a standard patent or, provided the parent application was filed before August 26, 2021, an innovation (i.e., 8-year) patent.

Under s 79C of the Act, divisional applications for an innovation patent may also be filed during the period from grant (following formalities examination) up to one month after the advertisement of certification (following substantive examination) of the parent innovation patent.

Subject Matter Limitations

Divisional applications can be filed for further inventions disclosed in the parent application, particularly in cases of a lack of unity or multiple disclosed but unclaimed inventions. The only subject matter limitation is that the divisional application must be for an invention disclosed in the parent application. However, it is possible to add new subject matter when filing a divisional application (including adding a missing best method, as discussed below). A divisional application will be entitled to divisional status provided it includes disclosure of an invention disclosed in the parent application; however, the priority date of each claim will be assessed based on the priority date that claim would have had if it were in the parent application.

Double Patenting Concerns

Australia applies a "same invention" standard for double patenting, as established under sections 64(2) and 101B(2)(h) of the Act. This approach is less restrictive than jurisdictions like the United States and Canada, which apply both "same invention" and "obviousness-type" standards.  Under Australian practice, overlapping claim scope between a divisional and its parent is permitted. However, a patent cannot be granted if it claims identical or substantially identical subject matter to a granted patent in the same family. The test typically applied asks whether, if the claims of two specifications were in the same specification, there would be redundancy of claiming.

Australian examiners generally consider double patenting during examination when a related parent or divisional case is pending or has been granted and will raise objections if appropriate. This proactive approach helps identify potential issues early in the prosecution process and aims to two patents being granted for the same invention. However, in the event the issue is not picked up during examination, double patenting is not a ground of revocation in Australia.

Best Method Requirements for Divisional Applications

The Traditional Requirement

Australia remains one of the few jurisdictions that maintains a "best method" or "best mode" requirement under section 40(2)(aa) of the Act. This provision requires that a complete specification "disclose the best method known to the applicant of performing the invention" at the filing date.

Recent Judicial Clarification

A significant development in divisional patent practice occurred in 2018, when the Federal Court in Dometic Australia Pty Ltd v Houghton Leisure Products Pty Ltd [2018] FCA 1573 found, contrary to conventional thinking, that the best method requirement for divisional applications was to be assessed at the time of filing the complete specification for the divisional application, rather than the original complete specification filing date. This decision necessitated supplementing divisional applications with the disclosure of the best method at the time of filing.

In 2025, the Federal Court revisited this approach in The NOCO Company v Brown and Watson International Pty Ltd [2025] FCA 887. Justice Moshinsky clarified that for divisional patents, the best method requirement is assessed by reference to the applicant's knowledge when the earliest related complete application (including a PCT application) was filed, not when the divisional application itself was filed.

The NOCO decision resolved the uncertainty that arose following Dometic, representing a return to common-sense principles. While it is possible this issue could be revisited by another single judge or full bench of the Federal Court, the NOCO is more closely aligned with the Full Federal Court's prior reasoning in Pfizer Overseas Pharmaceuticals v Eli Lilly & Co [2005] FCAFC 224.

Practical Implications

The Australian Patent Office has quickly adopted the NOCO reasoning, amending the examination manual to reflect that, for divisional applications, the relevant date is the filing date of the earliest application, the date from which the patent term is calculated. This clarification removes significant complications that arose from assessing the best method at the later divisional filing date, including questions about knowledge requirements, added subject matter, and priority rights, while still allowing for a lack of best method as at the original filing date to be remedied by filing a divisional application.

Enhanced Supervision for Complex Divisional Chains

The Australian Patent Office occasionally changes its approach to divisional management, requiring practitioners to stay alert to the evolving procedural requirements. The Patent Office has, at varying times, adopted a practice of introducing a short (two-month) response time frame for responding to examination reports on divisional applications that substantially repeat the objections raised in respect of an ancestor application. While this practice is currently suspended, Australian divisional practice still involves enhanced supervision for divisional applications with great-grandparent or earlier ancestors.

to minimize the practice of "daisy chaining" divisional applications, which can create perpetual pendency and burden third parties, where the examiner determines that no progress is being made, the case may be discussed with the Supervising Examiner, including consideration of case management or hearings to ensure prompt resolution.

The Patent Office also seeks to minimize perpetual pendency by routinely issuing directions to request examination of a divisional application within 1-2 months of filing. While divisional applications currently enter the normal examination queue after the request for examination has been filed, this practice is subject to change, particularly when an unexamined parent application is still pending and/or when the divisional application has been filed with the same claims as the parent application.

Patent attorneys must balance the legitimate strategic reasons for filing divisional applications, such as pursuing additional inventions, tailoring claims to capture infringers, extending prosecution time, or maintaining pending applications for litigation purposes, against the heightened scrutiny and changing procedure applied to complex divisional chains.

Key Takeaways

Filing divisional applications in Australia requires careful attention to several critical factors that have evolved significantly in recent years:

Timing is Essential: A strict three-month deadline for filing standard divisional applications after advertisement of acceptance of the parent application applies. 

Double Patenting Standards are Manageable: Australia's "same invention" standard allows overlapping claim scope between parent and divisional applications, provided identical claims are avoided. This offers greater flexibility than more restrictive jurisdictions.

Best Method Assessment Date is Clarified: The recent NOCO decision confirms that best method requirements for divisional applications are assessed at the earliest complete application filing date, not the divisional filing date. This removes significant compliance complications and aligns with practical patent term considerations.

Complex Divisional Chains Face Enhanced Scrutiny: Applications with great-grandparents or earlier ancestors are currently subject to heightened examination supervision and potential case management to prevent abuse of the divisional system.

Strategic Planning is Critical: The enhanced supervision for complex divisional chains requires careful prosecution planning to demonstrate progress and avoid triggering case management procedures that add cost and uncertainty.

As Australia continues to refine its divisional application procedures, practitioners must remain vigilant to these evolving requirements while maintaining focus on the fundamental goal of securing appropriate patent protection for their clients' innovations. Recent developments reflect a maturing system that balances legitimate strategic needs with the prevention of procedural abuse, requiring sophisticated practice management to navigate successfully.

This post was written by Lisa Mueller and Claire Gregg of Davies Collison Cave