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CIPO’s March 2026 Practice Notice: What Changed, What It Means, and How It Affects Prosecution

April 22, 2026

Part 1 of a 4-part series on subject matter eligibility after CIPO’s March 2026 Practice Notice

On March 24, 2026, the Canadian Intellectual Property Office released a new Practice Notice on patentable subject matter, replacing PN2020-04 and responding to recent Federal Court of Appeal decisions.

For practitioners prosecuting computer-implemented inventions, the update changes both the analytical framework and how eligibility arguments are developed in practice.

Understanding what has changed, and how those changes affect drafting and prosecution strategy under the new framework in practice, will inform how applications are drafted and prosecuted going forward.

What Changed

Removal of “actual invention” as a standalone inquiry

The March 2026 Notice removes the “actual invention” as a separate step following purposive construction. The analysis now focuses on the construed claims, with the nature of the invention assessed as part of purposive construction rather than through a separate inquiry.

Purposive construction now focuses on the nature of the invention

Under PN2020-04, purposive construction was often framed in terms of defining the boundaries of the claimed monopoly. The new Notice shifts the focus to identifying the nature of the invention based on the specification and the claims.

In doing so, examiners are directed to consider the specification as a whole, including what is presented as common general knowledge. Elements described as well-known, conventional, or with limited detail may be treated as forming part of that knowledge.

Elimination of the problem-solution approach

The problem-solution framework has been removed. The Notice no longer requires a technological problem or solution, nor a connection to the manual or productive arts. Subject matter assessment is instead grounded in a “holistic appreciation” of the patent and its claims.

The Schlumberger question for computer-implemented inventions

For inventions where the only physical element is the computer system, the Notice introduces the “Schlumberger question”: whether the claimed invention differs from programming a mathematical formula into a computer.

Where the Schlumberger question is asked, “something more” is required to meet the physicality requirement. In effect, this asks whether the claims are directed only to an algorithm implemented on a computer. Where that is the case, the claims risk being treated as indistinguishable from Schlumberger. The Notice indicates that if the claimed invention improves the functioning of the computer itself, for example through reduced memory usage, faster processing, or improved task-specific performance, the physicality requirement can be satisfied through that improved operation.

How the Analysis Operates in Practice

Detailed purposive construction

As seen in the accompanying examples, the purposive construction analysis now includes a description of the person skilled in the art (someone skilled in X, someone skilled in Y…), the common general knowledge,  a summary description of the specification (The specification appears to be directed to…), the nature of the invention, and what are considered essential elements.

Treatment of common general knowledge

The examples show that elements may be treated as common general knowledge where the specification provides limited detail. This affects how essential elements are interpreted in the eligibility analysis.

In practice, this means that insufficiently described elements may be characterized as conventional background rather than as part of the invention itself. The level of technical detail in the specification can therefore directly influence whether those elements are treated as essential in the eligibility analysis.

Focus on what has been “discovered”

In the accompanying examples, the analysis often turns on whether anything beyond an abstract algorithm has been identified. In substance, the analysis asks whether anything has been identified beyond the algorithm itself. Where the invention is characterized as only a known or abstract algorithm implemented on a computer, the claims are treated as indistinguishable from Schlumberger.

This approach appears across multiple examples, including those involving financial models and machine learning systems.

Prosecution Takeaways

Specifications should include sufficient technical detail

Where an invention relies on specific computational techniques, system configurations, or processing steps, the specification should describe those elements with enough detail to support their characterization as part of the invention rather than as common general knowledge.

Computational improvements should be identified explicitly

Where the invention improves the operation of a computer, whether through reduced computation, memory usage, or processing time, those improvements should be clearly described as part of the invention. These types of improvements are specifically identified in the Notice as supporting the physicality requirement and will often be central to distinguishing the claims from Schlumberger.

Claim drafting should reflect the technical contribution

Claims that present the invention as an algorithm implemented on a computer remain vulnerable to Schlumberger-type analysis. Claims should therefore incorporate, as essential elements, the technical features that provide the computational improvement or otherwise define how the computer is made to operate differently.

Prosecution strategies should be adapted to the new framework

Approaches based on the problem-solution framework or similar structured analyses no longer align with the current guidance. Responses should instead engage directly with how the examiner has characterized the invention, and rely on the technical disclosure in the specification to support a characterization that emphasizes the claimed technical contribution and its effect on computer operation.

Conclusion

The March 2026 Practice Notice introduces a different framework for assessing subject matter eligibility. Its practical effect is to place greater weight on how the invention is described, how its technical contributions are articulated, and how those contributions are reflected in the claims.

The prosecution implications of this framework vary by technology. We address those implications for artificial intelligence, quantum computing, and software and fintech inventions in the companion posts in this series.