By Sean Kelley and Jay-R Estavillo

In Australia, a divisional application is a separate patent application filed based on an existing ‘parent’ application. Filing a divisional application allows an applicant to pursue a new claim set directed towards subject matter disclosed in the parent application with the claims of the divisional application retaining the parent’s priority date where the earlier disclosure adequately discloses the claimed invention. Each divisional is examined separately, can proceed independently to grant and can serve as the parent of another divisional.

To qualify as a divisional application, an Australian patent application must identify an eligible parent, be filed by an entitled applicant within the applicable deadline, and include at least one claim entitled to priority through the parent.

The divisional application should also meet the ordinary patentability and disclosure requirements. Its claims must be clear, succinct and supported by its specification, the specification must enable the claimed invention and the specification must disclose the best method of performing the invention known to the applicant when the divisional is filed.

Adding Subject Matter to Divisional Applications

An applicant may include additional subject matter when filing a divisional application and can pursue claims directed to that subject matter. Claims to new subject matter first disclosed in the divisional generally have the divisional’s filing date as their priority date and claims to combinations of subject matter disclosed in the original filing and new subject matter of the divisional also typically have the divisional’s filing date as their priority date (although this can be case-specific).

Recent Case Law

Two 2026 Australian court decisions,  The NOCO Company v Brown & Watson International Pty Ltd [2026] FCAFC 44 (“NOCO”) and Orikan Group Pty Ltd v Vehicle Monitoring Systems Pty Ltd (No 2) [2026] FCA 407 (“Orikan”), are important to consider when developing new Australian divisional filing strategies, and in particular, when considering the “best method” requirement of Australian patent applications.

NOCO concerned three Australian divisional patents for portable vehicle battery jump starters with safety protection, Australian Patent Nos. 2020201223, 2021258059, and 2022201338. The technology of the patents addressed risks arising when battery clamps touch each other or are connected with incorrect polarity.

Claim 1 of the original PCT application, filed on 3 July 2014, recited a jump-starting apparatus with:

• An internal power supply.
• An output port with positive and negative outputs.
• A vehicle battery isolation sensor configured to detect the presence of a connected vehicle battery.
• A reverse polarity sensor configured to detect the polarity of the connected battery.
• A power FET switch connected between the internal power supply and the output port.
• A microcontroller configured to turn on the FET switch in response to signals from the two sensors indicating battery presence and correct polarity.

Claim 1 of the PCT application expressly required the power FET switch. The Detailed Description implemented that switch using three FETs connected in parallel and did not disclose any alternative switching arrangement in relation to the invention.

NOCO launched its jump starter product in September 2014. The product reflected the embodiment described in the PCT application, including a switching arrangement using three FETs in parallel. Following launch, NOCO encountered problems with the battery’s discharge capability and the FET switching arrangement. Internal NOCO correspondence revealed in the later litigation included NOCO’s president stating the battery needed to be larger and an engineer suggesting replacing the FET switching arrangement with a relay. NOCO implemented improvements in late 2014 and early 2015.

Several years later, NOCO filed the three Australian divisional applications on 20 February 2020, 29 October 2021 and 25 February 2022 and prosecuted them to grant. Many of the divisional claims omitted the FET limitation, seeking protection broad enough to encompass other switching arrangements. The Detailed Description of the divisional applications was kept largely consistent with the originally filed PCT application, so referred only to the FET switch arrangement.

NOCO subsequently sued Brown and Watson International, alleging that its jump starters infringed the three divisional patents. In the 2026 appeal decision, the Full Court held that the asserted claims were invalid for lack of inventive step and failure to disclose the best method known to NOCO when the divisionals were filed. Many asserted claims also lacked novelty after losing entitlement to the original PCT priority date.

The best-method finding arose because NOCO had improved the product’s battery and replaced the unreliable FET switching arrangement with relays before filing the divisionals. These improvements concerned core features of the claimed invention, but the divisional specifications continued to describe only the earlier implementation (that is, the description was not updated to describe the new implementation, which was known to NOCO to be the best method of performing the invention, and which had been implemented in its commercial product). The Court held that each divisional had to disclose the best method known at its own filing date. It expressly noted that NOCO had removed the FET limitation from the relevant claims while leaving the improved switching arrangement undisclosed.

Many asserted claims also lost entitlement to the original PCT priority date. The PCT consistently presented the FET switch and separate battery-presence and polarity sensors as essential features. The broader divisional claims encompassed other switching or sensing arrangements that the PCT did not disclose. Those claims therefore could not retain the earlier priority date and, as a result were also invalidated for lack of novelty.

The technology of the Orikan case related to vehicle-detection for parking enforcement. Orikan’s predecessor, SARB, filed the PCT application in 2008 and the relevant Australian divisional on 7 August 2013. The claims involved the use of magnetic sensors to detect when vehicles arrived at and left parking spaces, and software to determine whether they had overstayed or otherwise breached parking restrictions.

In Orikan, Vehicle Monitoring Systems alleged that the claims of Orikan’s divisional patent were invalid because the specification failed to disclose the best method known to SARB of performing the invention when the divisional application was filed. The best-method challenge focused on two aspects of the invention, the method of detecting vehicles and determining parking violations, and the transmission of data between the detection units and parking officers’ devices.

Internal technical documents produced by Orikan on discovery, including specifications updated between the PCT and divisional filings, showed that SARB knew of better ways to carry out the patent’s vehicle-detection step before filing the divisional. These involved how the detection unit interpreted magnetic sensor readings to decide whether a vehicle was present. The Court found that SARB’s undisclosed vehicle detection methods formed part of the best method of performing the claimed invention and should have been included in the divisional specification.

The internal technical documents also described how SARB transmitted data from the detection units to parking officers’ handheld devices. They included details of communications equipment and protocols that were also not described in the divisional specification. The Court found that these details described SARB’s particular implementation of the communications system, but the evidence did not establish that it was a better method of performing that part of the claimed invention.

So, the key best-method outcomes of NOCO and Orikan were:

• In NOCO, the asserted claims were held invalid because the divisional specifications as filed did not disclose the improved relay switching arrangement and battery configuration known to NOCO to solve technical problems with the system as originally described in the PCT specification. The Court considered these improvements to core components to form part of the best method of performing the claimed invention.
• In Orikan, the asserted claims were held invalid because the divisional specification as filed did not disclose SARB’s formula for interpreting magnetic sensor readings and its improved vehicle-detection methodology. The Court found that these formed part of the best method known to SARB of performing the claimed invention when the divisional was filed.
• However, SARB’s omission of additional details about its communications equipment and protocols did not establish a failure to disclose the best method. The evidence showed a particular implementation of the communications system without establishing that it provided a better method of performing that part of the invention.

Preparing Australian Divisional Applications Post-NOCO and Orikan

Standard practice to-date in Australia has been to file divisional applications with largely the same description as the parent specification, with changes to the specification limited to updating the statements of invention in the Summary to reflect the new claims of the divisional. The NOCO and Orikan decisions raise questions about the extent to which product developments occurring after the parent application is filed, but before a divisional is filed, need to be considered when preparing the divisional application, and which of those developments must be disclosed in its specification.

NOCO and Orikan indicate that the practice to be adopted going forward should include:

• Settling the proposed divisional claims and identifying the invention they define, read with the specification as a whole.
• Checking with the applicant and inventors whether developments since the parent filing provide a better way of performing that invention, including improvements to essential features or components of the claimed combination. The focus should be on what those developments achieve, rather than simply whether the commercial product has changed.
• Assessing whether the existing description adequately discloses the best method now known. If it does, additional disclosure is likely unnecessary. However, broad language or general references to alternatives like those typically included at the end of a detailed description may not be sufficient.
• Including any necessary additional disclosure in the divisional specification when it is filed.
• Separately checking support, enablement and priority, particularly where the proposed claims are broader than the original disclosure or claims. Adding best-method information does not automatically mean the claims lose priority, but claims dependent on newly disclosed subject matter may not retain the parent’s priority date.

It is important to note that NOCO’s original PCT specification confined its switch disclosure narrowly to a FET arrangement, without describing any alternative switch implementations. The precedent set by the case is therefore of materially lower risk to applicants whose original specifications comprehensively describe the invention and relevant alternative implementations of the key features of the invention.

Importantly, not every development in the applicant’s commercial product requires additional disclosure in a divisional. The question is whether a development known to the applicant at divisional filing forms part of the best method of performing the invention claimed in the divisional, read with the specification as a whole, and whether that method is already adequately disclosed. A comprehensive original description may already disclose the best method known at divisional filing, making further disclosure unnecessary. Further, a development unrelated to performing the claimed invention does not require disclosure merely because it improves the commercial product.

Australian Divisional Filing Strategies Going Forward

Where multiple inventions or claim sets of different scope are to be pursued, one option for avoiding best-method issues arising from later developments is to file separate Australian Convention applications at the PCT filing date, with a claim set for each invention. This brings filing costs forward but fixes the relevant best-method date for those applications at a point in time (i.e. the PCT filing date) at which the best method known to the applicant will unambiguously be described in the patent specification.

As this may not be practical for some applicants, or it may not be known until later that multiple inventions or claim sets of different scope are to be pursued, an alternative option is to file the divisionals at or shortly after national phase entry, completing the above analysis and tailoring each specification, if required, to disclose product developments since the PCT filing date.

Otherwise, daisy-chaining the divisionals, completing the analysis each time a new divisional is filed, remains an available option.

Publication timing also requires attention when developing the Australian divisional strategy. Australian divisional applications filed more than 18 months after priority ordinarily publish shortly after filing. New developments added to a divisional specification may therefore become public before a later-filed patent family covering those developments publishes. The practical balance is between meeting the divisional’s disclosure requirements and securing appropriate priority protection in the later family before publication.

After NOCO and Orikan, there is still uncertainty about the required level of disclosure of new developments to satisfy the best method requirement and in practice, the required additional disclosure, if any, will be fact-specific. As a result, for particularly important patent families, or where litigation is likely, we recommend keeping a divisional application pending during the commercially valuable life of the patent family, even where claims of acceptable scope have been granted in a parent application. This strategy preserves the ability to file another daisy‑chained divisional application with supplemental best-method description if a problem comes to light during enforcement proceedings.