Patentable Subject Matter: What Can and Cannot Be Patented

The scope of patentable subject matter defines the threshold question in every patent application: whether an invention falls within the category of subject matter Congress intended to protect under federal law. Governed primarily by 35 U.S.C. § 101 and interpreted through decades of U.S. Supreme Court doctrine, this framework determines whether a claimed invention even qualifies for examination — before novelty, non-obviousness, or utility are assessed. The boundaries between eligible and ineligible subject matter remain among the most actively litigated questions in U.S. patent law, with particular intensity in software, biotechnology, and diagnostic method claims.

• Definition and scope
• Core mechanics or structure
• Causal relationships or drivers
• Classification boundaries
• Tradeoffs and tensions
• Common misconceptions
• Checklist or steps
• Reference table or matrix
• References

Definition and scope

Patentable subject matter in the United States is defined by 35 U.S.C. § 101, which states that "whoever invents or discovers any new and useful process, machine, manufacture, or composition of matter, or any new and useful improvement thereof, may obtain a patent." The statute identifies four statutory categories of eligible subject matter: processes, machines, manufactures, and compositions of matter. These categories have been interpreted broadly by courts, but they carry three judicially created exceptions that carve out significant terrain.

The U.S. Supreme Court has consistently held that laws of nature, natural phenomena, and abstract ideas are not patentable — not because Congress excluded them explicitly, but because the Court treats them as the basic tools of scientific and technological work that must remain freely available. This framework is explored comprehensively through section-101-patent-eligibility, which addresses the full doctrinal history of the exclusions.

The United States Patent and Trademark Office (USPTO) administers examination under § 101 through its January 2019 Revised Guidance, which provided examiners with a structured framework for applying Supreme Court precedent to pending applications. That guidance does not carry the force of law but shapes examination practice across all technology centers.

Core mechanics or structure

A § 101 eligibility analysis proceeds in two steps, articulated by the Supreme Court in Alice Corp. v. CLS Bank International, 573 U.S. 208 (2014), building on Mayo Collaborative Services v. Prometheus Laboratories, 566 U.S. 66 (2012).

Step One — Statutory Category: The examiner determines whether the claim is directed to one of the four statutory categories: process, machine, manufacture, or composition of matter. Claims that fall outside all four categories are immediately ineligible. This threshold is rarely the sticking point in practice.

Step Two — Judicial Exceptions (the Two-Part Alice/Mayo Test):

• Step 2A, Prong 1: The examiner determines whether the claim is directed to a judicial exception — a law of nature, natural phenomenon, or abstract idea. The USPTO's 2019 Revised Guidance groups abstract ideas into three sub-categories: mathematical concepts, certain methods of organizing human activity, and mental processes.

• Step 2A, Prong 2: If a judicial exception is identified, the examiner asks whether the claim integrates that exception into a practical application — meaning whether additional claim elements apply, use, or reflect on the exception in a manner that imposes a meaningful limit beyond the exception itself.

• Step 2B: If integration into a practical application is not found, the examiner determines whether additional elements provide an inventive concept — something significantly more than the exception alone. Conventional, well-understood, or routine activity does not satisfy this requirement.

The full patent-examination-standards framework places § 101 analysis at the front of examination, preceding §§ 102, 103, and 112.

Causal relationships or drivers

The current strictness of § 101 analysis traces directly to a sequence of Supreme Court decisions spanning 2010–2014. Bilski v. Kappos, 561 U.S. 593 (2010), rejected the "machine-or-transformation" test as the sole test for process eligibility and invalidated a business method patent on a commodity hedging process. Mayo (2012) invalidated diagnostic method claims covering the relationship between drug metabolite levels and dosing — finding that the steps added to a natural law were routine. Association for Molecular Pathology v. Myriad Genetics, 569 U.S. 576 (2013), invalidated claims to isolated natural DNA sequences while preserving claims to cDNA. Alice (2014) applied the Mayo framework to software-implemented financial methods, broadly invalidating abstract-idea claims that lacked an inventive concept.

These decisions created a significant upstream effect on patent prosecution: the USPTO's grant rate for software and business-method applications declined sharply in the years following Alice. The regulatory-context-for-patent-law page documents how Congressional debate over § 101 reform has proceeded without enacted legislation as of 2024, leaving the judicial framework intact.

Industry-specific pressure is equally significant. Biotechnology and pharmaceutical applicants face § 101 rejections when claims reach too close to natural correlations or genomic sequences. Software applicants face rejections when claims recite generic computer implementation of abstract methods. These pressures directly shape how patent-claims-drafting strategies are developed to satisfy eligibility while preserving competitive scope.

Classification boundaries

Eligible subject matter — confirmed categories:

• Software-implemented inventions that produce a specific technical improvement to a computer or computer-related process (post-Enfish, LLC v. Microsoft Corp., 822 F.3d 1327 (Fed. Cir. 2016))
• Genetically modified organisms with markedly different characteristics from naturally occurring organisms (Diamond v. Chakrabarty, 447 U.S. 303 (1980))
• Synthetic DNA (cDNA) not found in nature (Myriad Genetics, 2013)

Ineligible subject matter — confirmed exclusions:

The software-patent-law and biotechnology-patent-law pages address the classification questions specific to those technology domains in greater depth.

Tradeoffs and tensions

The § 101 framework generates a fundamental tension between two competing policy interests. Broad eligibility maximizes the incentive to invest in research and development by allowing innovators to capture value across a wide range of discoveries. Narrow eligibility preserves the commons of basic scientific knowledge — laws of nature, mathematical truths, natural correlations — that downstream innovators need to build further inventions.

The Alice/Mayo framework has been criticized from both directions. The biotechnology industry, represented through organizations including the Biotechnology Innovation Organization (BIO), has argued that the framework creates uncertainty for diagnostic and therapeutic method patents that represent genuine inventive effort. The Electronic Frontier Foundation and other technology-access advocates have argued that pre-Alice software patent grants captured too much abstract territory, enabling assertion campaigns against independently developed products.

A second tension exists between claim scope and eligibility. Narrow claims are more likely to survive § 101 scrutiny but provide thinner competitive protection. Broad claims may capture the functional core of an invention but risk reciting the exception itself without sufficient integration. This dynamic directly affects patent-portfolio-management strategy, particularly in sectors where rapid follow-on innovation can design around narrow claims.

A third tension involves international harmonization. The European Patent Convention excludes "discoveries, scientific theories and mathematical methods" and "mental acts, playing of games, doing of business" as such (EPC Art. 52), but European practice applies these exclusions with different granularity than the Alice framework, creating divergent prosecution outcomes for the same application filed under the patent-cooperation-treaty.

Common misconceptions

Misconception 1: "Software cannot be patented."
Software as such is not categorically excluded from patent protection under U.S. law. The Alice decision does not bar software patents — it bars software claims directed to abstract ideas without an inventive concept or practical application. Claims that recite specific improvements to computer functionality, particular data processing architectures, or technical solutions to technical problems have survived § 101 review in the Federal Circuit. The software-patent-law page catalogs the claim structures that have been upheld.

Misconception 2: "A new discovery in nature is automatically patentable."
Discovering a previously unknown natural phenomenon does not confer patent eligibility on claims directed to that phenomenon itself. Myriad Genetics confirmed that the act of isolating a naturally occurring DNA sequence — even after significant research effort — does not make the sequence patent-eligible. The inventive contribution must transform or apply the discovery beyond its natural state.

Misconception 3: "§ 101 is the only eligibility hurdle."
Even claims that clear § 101 must satisfy novelty-requirement-patents under § 102, non-obviousness-requirement under § 103, and written description and enablement requirements under § 112. The patent-eligibility-requirements page addresses the full four-factor framework.

Misconception 4: "Business methods are categorically unpatentable after Bilski."
The Supreme Court in Bilski explicitly declined to hold business methods categorically excluded from § 101. The decision invalidated the specific claims at issue as directed to an abstract idea. Business method claims tied to specific machine implementations or producing concrete technical results remain potentially eligible.

Checklist or steps

The following sequence reflects the USPTO's examination framework under § 101 as set out in the 2019 Revised Guidance. This is a procedural reference sequence, not legal advice.

Stage 1 — Statutory Category Confirmation
- [ ] Identify the independent claims to be analyzed
- [ ] Confirm each claim falls within at least one of the four statutory categories: process, machine, manufacture, or composition of matter
- [ ] If no statutory category applies, the claim is ineligible without further analysis

Stage 2A — Judicial Exception Screening

Prong 1 — Identify the Exception:
- [ ] Determine whether the claim is directed to a mathematical concept (mathematical relationships, formulas, calculations)
- [ ] Determine whether the claim is directed to certain methods of organizing human activity (fundamental economic principles, commercial interactions, managing personal behavior)
- [ ] Determine whether the claim is directed to a mental process (steps performable in the human mind, including observation, evaluation, judgment, or opinion)
- [ ] Determine whether the claim is directed to a law of nature or natural phenomenon

Prong 2 — Practical Application Integration:
- [ ] Identify additional claim elements beyond the exception
- [ ] Determine whether those elements reflect a specific technical improvement to technology
- [ ] Determine whether those elements apply the exception with a particular machine or transformation
- [ ] Determine whether those elements impose a meaningful limitation beyond the exception itself

Stage 2B — Inventive Concept (if Prong 2 not satisfied)
- [ ] Determine whether the additional elements are well-understood, routine, and conventional
- [ ] If all additional elements are conventional, the claim fails § 101
- [ ] Document specific findings for each element identified as conventional

Reference table or matrix

Additional context on the scope of protectable inventions across technology sectors is available from the patent law overview at the site index.