MPEP 2106: Patent Subject Matter Eligibility Under 35 U.S.C. 101

The statute is one sentence: "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 therefor, subject to the conditions and requirements of this title." "Process" is defined to include "a new use of a known process, machine, manufacture, composition of matter, or material" (§ 100(b)).

The courts have read into § 101 three judicial exceptions: abstract ideas, laws of nature and natural phenomena (including products of nature). The Supreme Court’s concern, as the MPEP summarizes it, is that these "are the basic tools of scientific and technological work," and patents on them could impede innovation. But a claim is not ineligible simply because it involves an exception; integrating one into a practical application may be eligible.

Eligibility is separate from novelty. The MPEP warns that the search for an inventive concept "should not be confused with a novelty or non-obviousness determination," quoting the Federal Circuit: "a claim for a new abstract idea is still an abstract idea." The novelty side is covered in our 35 U.S.C. 102 guide.

Sources: 35 U.S.C. § 101; 35 U.S.C. § 100(b); MPEP § 2106, subsection I; MPEP § 2106.05, subsection I.

Three working rules apply throughout. Each step is applied after the examiner has determined what the inventor invented by reviewing the whole disclosure and construing the claim under its broadest reasonable interpretation. Eligibility is decided claim by claim: a dependent claim may be eligible when its independent claim is not, and the reverse. And whether or not a § 101 rejection is made, the examiner must fully examine every claim under the other requirements, including §§ 102, 103 and 112.

Sources: MPEP § 2106, subsection III (flowchart and Pathways A-C); MPEP §§ 2106.03, 2106.04, 2106.05, 2106.07.

Step 1 asks: "Is the claim to a process, machine, manufacture or composition of matter?" The first is an action (a series of steps); the other three are things. The MPEP gives non-limiting examples of claims that fall outside every category:

• Products without physical or tangible form, such as information ("data per se") or a computer program claimed as a product without structural recitations ("software per se").
• Transitory forms of signal transmission ("signals per se"), such as a propagating electrical or electromagnetic signal or carrier wave.
• Subject matter the statute expressly prohibits, such as humans per se.

A claim whose broadest reasonable interpretation covers both statutory and non-statutory embodiments fails Step 1, such as a machine-readable medium that could be a compact disc or a carrier wave. Examiners are told to recommend a narrowing amendment where possible.

Source: MPEP § 2106.03.

Prong One asks whether a judicial exception is "set forth or described" in the claim. The MPEP stresses the difference between a claim that recites an exception (which needs further analysis) and one that merely involves one (which is eligible without more). "A machine comprising elements that operate in accordance with F=ma" recites a law of nature; a teeter-totter claim is based on the law of the lever but does not recite it, so it is eligible at Pathway B.

For abstract ideas, the USPTO uses three enumerated groupings distilled from the case law:

An examiner who believes a limitation is abstract but outside all three groupings is treating it as a "tentative abstract idea"; a rejection on that basis must be approved by the Technology Center director, with a justification in the record.

The limits of "mental processes." A claim recites a mental process when its limitations can practically be performed in the human mind, but not when "the human mind is not equipped to perform" them. The 2024 AI update and the August 4, 2025 memorandum both say that claim limitations that encompass AI in a way that cannot practically be performed in the human mind do not fall within this grouping. The memorandum contrasts "training the neural network in a first stage using the first training set" (USPTO Example 39), which does not recite a judicial exception, with training an artificial neural network using "a backpropagation algorithm and a gradient descent algorithm" (Example 47), which recites mathematical calculations by name.

Laws of nature and products of nature. Natural products, and non-natural products that lack "markedly different characteristics from any naturally occurring counterpart," fall within the exception; a product is not eligible just because people made it.

Sources: MPEP §§ 2106.04, 2106.04(a), 2106.04(a)(3), 2106.04(b); 2024 Guidance Update on Patent Subject Matter Eligibility, Including on Artificial Intelligence, 89 FR 58128; USPTO memorandum, Reminders on evaluating subject matter eligibility (Aug. 4, 2025).

If the claim recites an exception, Prong Two asks whether the claim as a whole integrates it into a practical application. If so, the claim is not "directed to" the exception and is eligible. The MPEP lists the considerations the courts have used:

Prong Two does not ask whether the additional elements are well-understood, routine or conventional; that question belongs to Step 2B. Conventional elements can still integrate an exception, and examiners must give weight to all additional elements.

The improvements consideration, as revised in December 2025. The examiner first reads the specification to see whether it describes the invention in enough detail that a person of ordinary skill would recognize an improvement in computer functioning or another technology; the specification need not state the improvement expressly, but a bare, conclusory assertion is not enough. Then the claim must reflect the improvement, by including the components or steps that provide it, though it need not recite the improvement in words. Examiners are told to evaluate the claim "as a whole" and not to evaluate claims "at such a high level of generality" that potentially meaningful technical limitations are dismissed.

Sources: MPEP § 2106.04(d); Advance notice of change to the MPEP in light of Ex Parte Desjardins (Dec. 5, 2025), revising MPEP §§ 2106.04(d)(1) and 2106.05(a).

Step 2B asks whether the additional elements, individually and in combination, "amount to significantly more than the judicial exception." It is not a weighing test. Most of the work is carried over from Prong Two; what is new at Step 2B is that the examiner re-evaluates elements treated as insignificant extra-solution activity and asks whether the additional elements are more than well-understood, routine, conventional activity in the field.

A finding that an element is well-understood, routine and conventional is a factual determination that "must be expressly supported in writing" by one of four kinds of support: an express statement in the specification or by the applicant during prosecution, a court decision noting the element’s conventional nature, a publication showing it, or a statement that the examiner is taking official notice.

Source: MPEP §§ 2106.05, 2106.05(d).

Mayo Collaborative Services v. Prometheus Laboratories (2012) held ineligible process claims about thiopurine drug dosing. The claims recited natural correlations between metabolite levels and drug efficacy or harm, and their added steps told doctors "to engage in well-understood, routine, conventional activity previously engaged in by scientists in the field," which "is normally not sufficient to transform an unpatentable law of nature into a patent-eligible application of such a law."

Alice Corp. v. CLS Bank (2014) turned Mayo into a two-part framework. First, determine whether the claims are directed to a patent-ineligible concept. If so, consider the elements "both individually and ‘as an ordered combination’" to decide whether they "transform the nature of the claim" into a patent-eligible application, the search for an "inventive concept." The Court held the claims to a computer-implemented scheme for mitigating settlement risk "drawn to the abstract idea of intermediated settlement," and that "the mere recitation of a generic computer cannot transform a patent-ineligible abstract idea into a patent-eligible invention."

Sources: Mayo Collaborative Services v. Prometheus Laboratories, Inc., 566 U.S. 66 (2012); Alice Corp. Pty. Ltd. v. CLS Bank International, 573 U.S. 208 (2014); MPEP § 2106, subsection III. Federal Circuit eligibility decisions are summarized on our patent eligibility topic page.

The MPEP itself has not been republished since Rev. 01.2024 (current as of January 31, 2024). Later eligibility guidance is issued separately and listed by the USPTO:

The August 2025 memorandum contrasts Recentive Analytics v. Fox (Fed. Cir. 2025), where steps incidental to automating an abstract idea did not confer eligibility, with USPTO Example 47, claim 3, where the claim as a whole improved network intrusion detection. A Federal Register search on October 19, 2026 found no USPTO eligibility notice after the 2024 update and its September 2024 comment extension; the later items above are memoranda and a precedential decision, not rules.

Sources: USPTO subject matter eligibility page (updated Sept. 29, 2026); 89 FR 58128 (July 17, 2024); Aug. 4, 2025 memorandum; Dec. 4, 2025 SMED memorandum; Dec. 5, 2025 advance notice (Desjardins); Sept. 29, 2026 SMED memorandum; MPEP main page and updates; Subsequent Publications, July 2026 update; Federal Register search.

The rejection must set out a prima facie case of ineligibility, made only when it is more likely than not that the claim fails Step 1 or Step 2B. The sources point to these responses:

• Prong One: show the limitations merely involve an exception, or cannot practically be performed in the human mind.
• Prong Two: identify where the specification explains a technical improvement in enough detail, and which claim elements provide it.
• Step 2B: if the rejection calls an element conventional without one of the four kinds of written support, point that out.
• Evidence (SMEDs): an optional declaration under 37 C.F.R. § 1.132, signed by anyone with knowledge of the facts. The USPTO suggests filing it separately (Patent Center code "AF/D.SMED"), early (after prosecution closes, it is not timely unless certain conditions are met), with disinterested evidence where possible, saying which step it supports, and following up with an interview.

Common mistakes, in our reading of these sources: arguing novelty in response to a § 101 rejection; asserting an improvement the specification never explains; claiming the result without the steps that achieve it; and computer-readable-medium claims that could cover a transitory signal.

Sources: MPEP §§ 2106.04, 2106.04(d), 2106.05(d), 2106.07; Aug. 4, 2025 memorandum; Dec. 4, 2025 SMED memorandum; Sept. 29, 2026 SMED memorandum. The list of mistakes is our own. More on examination is on the patent prosecution hub, and eligibility is tested on the patent bar.