Unity of Invention under Australian Patent System

A fundamental principle that every application must satisfy is the “unity of invention.” While seemingly straightforward, this is a technical area of patent law that frequently gives rise to objections during examination. Failure to address unity issues correctly can delay prosecution, increase costs, and, if mishandled, result in the loss of valuable patent rights.

Understanding how unity of invention is assessed, and how to respond strategically when objections arise, is therefore essential for applicants seeking robust and commercially effective patent protection in Australia.

Requirement of a Single General Inventive Concept

Under the Australian patent system, a patent application must relate to one invention only or to a group of inventions so linked as to form a “single general inventive concept.” This requirement is reflected in the Patents Act 1990 (Cth), the Patents Regulations 1991, IP Australia’s examination practice, and is closely aligned with international standards under the Patent Cooperation Treaty (PCT).

The policy rationale is straightforward. The patent system is designed to ensure that each application can be searched and examined efficiently. Allowing multiple, unrelated inventions to be pursued in a single application would undermine that objective and impose an unreasonable burden on the examiner.

The core of the unity requirement is the “single general inventive concept.” This concept is identified by reference to the “special technical features” of the claimed inventions, those features that, for each claimed invention, specify its contribution over the prior art. If the same or corresponding special technical features are present in all the claims, the requirement for unity is met.

A well-drafted application will clearly articulate this unifying concept from the outset. Establishing a coherent inventive narrative is central to avoiding unity objections and ensuring smooth prosecution.

Lack of Unity Objections: A Priori and A Posteriori

During substantive examination, an IP Australia examiner will meticulously assess whether the claims of a patent application are unified by a single general inventive concept. If they conclude that the application encompasses more than one invention, a “lack of unity” objection will be raised. This is not a final rejection of the inventions’ patentability but a procedural objection that must be skillfully addressed. It does not mean the inventions themselves lack patentability; rather, it indicates that they cannot all be pursued within the same application. Unity objections typically arise in one of two ways: a priori or a posteriori.

A Priori Lack of Unity

An a priori lack of unity is evident “from the outset,” meaning it is identified before the examiner conducts a detailed search of the prior art. This objection is raised when the claims are, prima facie, directed to unrelated inventions. For example, if an application includes independent claims to A + X, A + Y, and X + Y, and there is no single technical feature common to all claims, the absence of a unifying inventive concept is immediately apparent. In such cases, the examiner can raise an a priori lack of unity objection without reference to prior art.

These objections are usually straightforward to diagnose and often require either claim consolidation or the filing of divisional applications.

A Posteriori Lack of Unity

More frequently, examiners raise an a posteriori lack of unity objection. This occurs “after the fact”, that is, after a search of the prior art reveals that the technical feature initially believed to be the “special technical feature” is actually already known.

When the common feature is found in the prior art, it can no longer be considered “special” or define a contribution over the art. Consequently, it loses its power as the unifying inventive link between the claims. As a result, the technical link between the claims collapses, and the examiner may conclude that the claims relate to multiple, distinct inventions.

For example, consider an application with claims to a transmitter (A) with a special circuit (X) and a receiver (B) with the same special circuit (X). A priori, the special circuit (X) appears to be the single general inventive concept linking the transmitter and receiver. However, if the examiner’s search discovers that circuit (X) is already known from a prior art document, it is no longer a “special” technical feature. The examiner will raise an a posteriori lack of unity objection, asserting that the transmitter and receiver now represent two separate, unlinked inventions.

This reasoning mirrors the situation in the European Patent Office case Teeth Whitening/UNILEVER, W 4/96, where a group of compounds was initially linked by a common function, but once the prior art showed this function was known for some of the compounds, the unifying link was lost. IP Australia and the Australian courts frequently look to these international decisions for guidance because Australia’s unity laws are harmonized with the PCT.

Common Scenarios giving rise to Unity Objections

Lack of unity objections can manifest in various forms, particularly in complex applications involving different types of claims or technologies.

Multiple Claim Categories

Australian practice permits to include claims of different categories in a single application, such as claims to a product, a process for making that product, and a use for that product. Unity is considered to be present if these claims are technically linked.

A process will typically be unified with a product if it is specially adapted to manufacture that product. Similarly, an apparatus may be unified with a process if it is specifically designed to carry out that process. The technical relationship must be substantive, not merely incidental. In the case of Caterpillar Tractor Co v Comm Pats 231 USPQ 591, the interpretation of “specifically designed” was key, establishing that the process and apparatus must be technically interconnected, not merely usable with each other.

Careful drafting is essential to demonstrate this technical linkage clearly and to avoid unity objections based on perceived disconnection between claim categories.

Markush Claims in Chemical and Biotechnological Inventions

In the chemical, pharmaceutical, and biotechnology applications, “Markush” claims are common. These claims define an invention by reciting a group of functionally equivalent alternatives (e.g., a selection of chemical compounds). For a Markush claim to possess unity, IP Australia requires that:

• all alternatives must share a common property or activity; and
• the alternatives either share a significant common structural element, or belong to a recognized class in the art.

The shared structural element need not be novel itself, but it must be significant. If the alternatives are structurally diverse, a unity objection is highly likely. The case Benzyl Esters/BAYER, T 110/82 established that unity can exist between final products and their intermediates if the intermediates incorporate an essential structural element of the final products, demonstrating a close technical interconnection.

Unsupported, Unclear, or Complex Claim Sets

Clarity and support are also tied to the question of unity. If a claim set is excessively long, unclear, internally inconsistent, or insufficiently supported by the description, the Examiner may raise a unity objection. This is because the lack of clarity makes it difficult, if not impossible, for the Examiner to determine the subject of the invention and, therefore, to identify a single general inventive concept for the purpose of a meaningful search.

Ensuring that claims are precise, well-supported, and clearly framed around the inventive contribution is therefore critical to avoiding procedural complications.

Responding Strategically to Lack of Unity Objections

A lack of unity objection requires a considered and strategic response. The appropriate course depends on the nature of the objection, the prior art cited, and the applicant’s commercial objectives.

Argument and Targeted Amendment

In some instances, a lack of unity objection can be overcome by presenting persuasive legal and technical arguments. This may involve demonstrating that the examiner has misconstrued the single general inventive concept or overlooked a subtle but crucial technical link between the claims. Strategic amendments to the claims can also be made to emphasize the unifying “special technical feature” and to more clearly delineate the invention from the prior art.

Such responses must be grounded in both technical reasoning and established examination principles.

Divisional Applications as a Strategic Solution

Where multiple inventions are genuinely present, or where protection for all aspects of the disclosure is commercially important, the filing of divisional applications is often the most effective solution. A divisional application is effectively a new application that is “divided” from the original parent application to pursue protection for the separate invention(s).

A divisional application allows the applicant to pursue protection for a separate invention disclosed in the original application, while retaining the original priority date. This enables applicants to:

• secure protection for multiple inventions without abandonment;
• allow the parent application to proceed efficiently to grant; and
• build a layered and strategically valuable patent portfolio.

Divisional filings are not merely reactive. When used proactively, they can significantly enhance the breadth, resilience, and commercial leverage of a patent family.

How can we Assist?

Unity of invention is a procedural requirement with substantive strategic consequences. While a lack of unity objection does not reflect on the patentability of the underlying inventions, it demands careful handling to avoid delay, unnecessary cost, or loss of rights.

A clear understanding of how unity is assessed, particularly the distinction between a priori and a posteriori objections, allows applicants to respond effectively and to use mechanisms such as divisional applications to their full advantage. When managed strategically, unity issues can be transformed from procedural obstacles into opportunities to strengthen and expand a patent portfolio.

Our firm will manage this entire process for you, from advising you on the strategic timing of the divisional filing to drafting and prosecuting the new application, ensuring all procedural requirements are met to safeguard your rights.

Contact us today for free consultation.