Section 112 Patent Review Checklist: A Practical Checklist

How to use this checklist

A Section 112 review compares two documents that were usually written by the same person in a hurry: what the claims cover and what the specification teaches. This checklist is built so that a second person can make that comparison cold.

Use Phases 0 through 6 before filing or before amending, and again before any assertion. Phase 7 is for prosecution. Phase 8 is for a patent owner preparing to send a letter or file suit. Phase 9 is for an accused infringer or challenger. Phase 10 applies to both sides in litigation. Print one copy per independent claim.

Each item names the governing authority. Notes explain why it matters. For the reasoning and case readings, read Enablement, Written Description, and Indefiniteness After Amgen v. Sanofi: What Section 112 Demands. For step-by-step drafting and litigation advice, read Drafting Patent Claims and Specifications That Survive Section 112: A Practical Guide. The worksheets that go with these tasks are in the Section 112 Toolkit: Claim Support Charts, Invalidity Contentions, and Expert Declarations.

Phase 0: Classify the patent and the claims

• Note the governing text. Applications filed on or after September 16, 2012 use 35 U.S.C. § 112(a), (b), and (f); earlier ones use paragraphs 1, 2, and 6. Cite accordingly. Note: The Federal Circuit has treated the differences as immaterial on these issues, but your pleading should name the right version.
• List each independent claim and classify it: composition, apparatus, system, method of making, method of use, or Jepson. Note: Method-of-use claims can be analyzed differently under Teva Pharmaceuticals International GmbH v. Eli Lilly & Co., No. 24-1094 (Fed. Cir. Apr. 16, 2026), and a Jepson preamble needs support under In re Xencor, Inc., No. 24-1870 (Fed. Cir. Mar. 13, 2025).
• Mark every limitation as structural, functional, or parametric. Highlight anything defined by what it does or by a number it achieves. Note: Parameter claims are functional in substance. See Brita LP v. International Trade Commission, No. 24-1098 (Fed. Cir. Oct. 15, 2025), where a performance factor covered any filter media.
• State the outer boundary in one sentence. "This claim covers every ____ that ____." If you cannot write that sentence, start with Phase 5.
• Note the art's predictability. Identify whether skilled people in this field can predict results from structure or code, and cite evidence. Note: In re Wands, 858 F.2d 731 (Fed. Cir. 1988), makes predictability a factor. The level of detail required for written description also varies with it under Ariad Pharmaceuticals, Inc. v. Eli Lilly & Co., 598 F.3d 1336 (Fed. Cir. 2010) (en banc).
• Collect the file: application as filed, every priority document, the prosecution history, inventor notebooks (under privilege review), and any later publications by the inventors.

Red flag: The claim's outer boundary sentence ends in a result rather than a thing. That is the shape of the claims in Holland Furniture, Amgen, and Baxalta.

Phase 1: Capture what the inventors actually did

• Interview the inventors on failures. Record what was tried, what failed, and the suspected reasons. Note: Intake forms in Preparing an Invention Disclosure: A Practical Checklist can be extended with these questions.
• Count. Number of candidates or approaches tested, number that worked, and the range they span. Note: In Baxalta Inc. v. Genentech, Inc., 81 F.4th 1362 (Fed. Cir. 2023), the record showed only 1.6% of screened antibodies had the claimed function.
• Ask for the common thread. What feature do the working embodiments share that the failures lack, and what evidence supports that? Note: This is the "quality common to every functional embodiment" left open by Amgen Inc. v. Sanofi, 598 U.S. 594 (2023).
• Separate done from predicted. Label every example as working (past tense) or prophetic (present or future tense). Note: Prophetic examples are permitted, Atlas Powder Co. v. E.I. du Pont de Nemours & Co., 750 F.2d 1569 (Fed. Cir. 1984), but dressing them as completed work creates a candor problem under 37 C.F.R. § 1.56. See Maintaining the Duty of Candor to Avoid Inequitable Conduct: A Practical Checklist.
• Identify what the art supplies. List what a skilled person already knew, with citations, and what only the inventors can teach. Note: The specification, not general knowledge, must supply the novel aspects. Genentech, Inc. v. Novo Nordisk A/S, 108 F.3d 1361 (Fed. Cir. 1997).
• Identify the best mode known today and include it. 35 U.S.C. § 112(a). Note: Its omission no longer invalidates, per 35 U.S.C. § 282(b)(3)(A), but the duty stands.

Red flag: Inventors cannot say why the invention works, and all examples came from one lineage, one data set, or one configuration.

Phase 2: Test the scope ladder

• Confirm at least one claim reads plainly on the product you need to protect.
• Confirm a rung exists at each commercially useful level: broad structural genus, narrower genus, named embodiments, method, and downstream product.
• For each rung, cite the paragraph, figure, and example supporting it. 37 C.F.R. § 1.75(d)(1).
• Rewrite any result-only rung to name a feature that identifies its members.
• Check that each dependent claim adds a limitation that independently supports validity, not merely a label.
• Identify the most likely design-around, and ask whether the specification actually teaches it. Note: A claim that reaches a design-around the specification does not teach invites Liebel-Flarsheim Co. v. Medrad, Inc., 481 F.3d 1371 (Fed. Cir. 2007).

Red flag: The broadest claim is the only claim that would cover the expected competitor. If it falls, there is nothing left to assert.

Phase 3: Enablement review

• Work through all eight Wands factors for each independent claim, in writing: quantity of experimentation, direction, working examples, nature of the invention, prior art, skill, predictability, and breadth. In re Wands. Note: The USPTO uses the same factors, 89 Fed. Reg. 1563 (Jan. 10, 2024). Courts see "no meaningful difference" between Wands' undue experimentation and Amgen's reasonableness language. Baxalta.
• Identify concrete embodiments at the far edge of the claim and ask how a reader would make each. Note: A challenger must do the same under McRO, Inc. v. Bandai Namco Games America Inc., 959 F.3d 1091 (Fed. Cir. 2020). Do it first.
• Ask whether the disclosed method is anything more than make and test. Note: A process that reliably produces at least one member can still be trial and error. Baxalta. Compare Amgen, 598 U.S. at 614.
• For sequence or structural percentages, test whether structure predicts function. Note: The nonprecedential Pioneer Hi-Bred International, Inc. v. Inari Agriculture, Inc., No. 25-1287 (Fed. Cir. Oct. 2, 2026), affirmed a Board finding of non-enablement on an 85% identity claim where two of eight tested variants worked.
• Read every "or" separately. Confirm each alternative can be made and used. Note: An express alternative that is physically impossible defeats enablement. Satius Holding, LLC v. Samsung Electronics Co., No. 25-1446 (Fed. Cir. Oct. 1, 2026).
• Check open-ended ranges ("at least," "greater than," "or more") against what was achieved. Note: See MagSil Corp. v. Hitachi Global Storage Technologies, Inc., 687 F.3d 1377 (Fed. Cir. 2012), and Medytox, Inc. v. Galderma S.A., 71 F.4th 990 (Fed. Cir. 2023).
• For treatment claims, check dose, regimen, and patient limitations against the data. Note: In vitro data alone will not carry an in-patient dosing limitation. Wyeth LLC v. AstraZeneca Pharmaceuticals LP, No. 24-2325 (Fed. Cir. July 9, 2026). Clinical proof is not generally required, United Therapeutics Corp. v. Liquidia Technologies, Inc., 74 F.4th 1360 (Fed. Cir. 2023), but guidance is.
• For method-of-use claims, decide which line applies. Known class, all members work: Teva. Efficacy varies and must be screened: Idenix Pharmaceuticals LLC v. Gilead Sciences Inc., 941 F.3d 1149 (Fed. Cir. 2019). Nothing known: University of Rochester v. G.D. Searle & Co., 358 F.3d 916 (Fed. Cir. 2004). Note: Teva drew a dissent from the denial of rehearing en banc on September 30, 2026, and remains subject to possible further review. Do not build a portfolio on it alone.
• Check whether the specification criticizes alternatives the claim covers. Note: Brita treated the patent's own statements as a warning against other filter types, following AK Steel Corp. v. Sollac, 344 F.3d 1234 (Fed. Cir. 2003).

Red flag: The sentence "the skilled artisan is aware of" or "may be determined by routine experimentation" stands where the novel step should be. Wyeth quoted that kind of sentence against the patent owner.

Phase 4: Written description and priority

• Chart each limitation of each claim against the earliest application you need, with pinpoint citations. Note: 35 U.S.C. § 120 and § 119(e) require the earlier filing to support the claim as § 112(a) requires. Lockwood v. American Airlines, Inc., 107 F.3d 1565 (Fed. Cir. 1997).
• Apply the four-corners test. Could a skilled reader recognize this claim in the text alone, without the inventor's explanation? Note: Ariad rejects notebooks and later possession as substitutes and states that a description rendering the invention obvious is not enough.
• For a genus, list the representative species or the common structural features. Check diversity against the likely accused products. Note: Juno Therapeutics, Inc. v. Kite Pharma, Inc., 10 F.4th 1330 (Fed. Cir. 2021); AbbVie Deutschland GmbH & Co. v. Janssen Biotech, Inc., 759 F.3d 1285 (Fed. Cir. 2014).
• For a subgenus or species drawn from a large list, find the blaze marks. Identify the text that singles it out. Note: Seagen Inc. v. Daiichi Sankyo Co., No. 23-2424 (Fed. Cir. Dec. 2, 2025), relying on In re Ruschig, 379 F.2d 990 (C.C.P.A. 1967).
• Check whether any generic claim outruns a single disclosed form. Note: LizardTech, Inc. v. Earth Resource Mapping, Inc., 424 F.3d 1336 (Fed. Cir. 2005); Gentry Gallery, Inc. v. Berkline Corp., 134 F.3d 1473 (Fed. Cir. 1998); ICU Medical, Inc. v. Alaris Medical Systems, Inc., 558 F.3d 1368 (Fed. Cir. 2009).
• Check negative limitations. Identify text that supports each exclusion. Note: Novartis Pharmaceuticals Corp. v. Accord Healthcare Inc., 38 F.4th 1013 (Fed. Cir. 2022).
• Check amendments for new matter. 35 U.S.C. § 132(a).
• Do not rely on original claims alone. They may not convey possession of a broad genus. Ariad.
• Identify intervening art if priority fails, including competitors' own products and publications. Note: See Prior Art Under the America Invents Act: Section 102, the On-Sale Bar, Public Use, and the One-Year Grace Period and the Prior Art Qualification Checklist: A Practical Checklist.
• Preview after-arising technology. If the accused technology did not exist at filing, ask whether the claim expressly claims it. Note: In re Entresto, 125 F.4th 1090 (Fed. Cir. 2025), and In re Hogan, 559 F.2d 595 (C.C.P.A. 1977).

Red flag: A continuation was filed after a competitor launched, and its new limitation reads on the competitor but appears nowhere in those words in the parent. Prepare for the inventors to be asked, "When did you first see this?"

Phase 5: Definiteness audit

• Run a word search for terms of degree and approximation: about, approximately, substantially, generally, sufficient, effective, high, low, thin, near, significantly, unobtrusive, similar.
• For each hit, find the anchor: a definition, test, numeric example, or comparison. Note: Nautilus, Inc. v. Biosig Instruments, Inc., 572 U.S. 898 (2014); Interval Licensing LLC v. AOL, Inc., 766 F.3d 1364 (Fed. Cir. 2014) (objective boundaries).
• Check examples for consistency with any tolerance you assert. Note: In Enviro Tech Chemical Services, Inc. v. Safe Foods Corp., No. 24-2160 (Fed. Cir. May 4, 2026), inconsistent pH deviations across experiments helped sink "about."
• For each recited number, name the measurement method. Ask whether other reasonable methods give different results. Note: Teva Pharmaceuticals USA, Inc. v. Sandoz, Inc., 789 F.3d 1335 (Fed. Cir. 2015); Dow Chemical Co. v. Nova Chemicals Corp., 803 F.3d 620 (Fed. Cir. 2015); HZNP Medicines LLC v. Actavis Laboratories UT, Inc., 940 F.3d 680 (Fed. Cir. 2019).
• Check user-dependent or taste-dependent terms. Note: Datamize, LLC v. Plumtree Software, Inc., 417 F.3d 1342 (Fed. Cir. 2005). Compare Sonix Technology Co. v. Publications International, Ltd., 844 F.3d 1370 (Fed. Cir. 2017), where examples and record evidence supported a similar-sounding term.
• Review words added by amendment, especially to overcome art. Note: See the nonprecedential Network-1 Technologies, Inc. v. Google LLC, No. 24-1893 (Fed. Cir. Apr. 23, 2026).
• Check system claims for user acts and mixed classes. IPXL Holdings, L.L.C. v. Amazon.com, Inc., 430 F.3d 1377 (Fed. Cir. 2005).
• Check antecedent basis, step order, and any internally contradictory requirement. Note: Synchronoss Technologies, Inc. v. Dropbox, Inc., 987 F.3d 1358 (Fed. Cir. 2021), found indefiniteness where a claim was nonsensical; the nonprecedential Indect USA Corp. v. Park Assist, LLC, No. 24-1023 (Fed. Cir. Jan. 7, 2026), rejected an impossibility reading.
• During prosecution, fix unclear terms now. The Office's standard is more demanding. In re Packard, 751 F.3d 1307 (Fed. Cir. 2014).

Red flag: A word of approximation sits next to a numeric limit that was amended to avoid close prior art. In Enviro Tech the court observed that the art was almost "about" the claimed value.

Phase 6: Functional language, software, and AI

• Flag every element whose noun is a placeholder: module, unit, mechanism, element, device, component, logic, handler, engine, manager, service. Note: Williamson v. Citrix Online, LLC, 792 F.3d 1339 (Fed. Cir. 2015); Rain Computing, Inc. v. Samsung Electronics Co., 989 F.3d 1002 (Fed. Cir. 2021); Fintiv, Inc. v. PayPal Holdings, Inc., 134 F.4th 1377 (Fed. Cir. 2025).
• Parse each flagged phrase into the function it recites and the term that performs it, and ask whether the claim says how. Note: TrackTime, LLC v. Amazon.com Services LLC, No. 24-1102 (Fed. Cir. July 2, 2026), directs this analysis.
• Gather field usage evidence for code terms: contemporaneous publications, products, and manuals. Note: Dyfan, LLC v. Target Corp., 28 F.4th 1360 (Fed. Cir. 2022), turned on unrebutted testimony about off-the-shelf code.
• For each functional element, locate the algorithm: inputs, outputs, and transformation in text, a flow chart, a formula, or code. Note: Aristocrat Technologies Australia Pty Ltd. v. International Game Technology, 521 F.3d 1328 (Fed. Cir. 2008); Finisar Corp. v. DirecTV Group, Inc., 523 F.3d 1323 (Fed. Cir. 2008); Typhoon Touch Technologies, Inc. v. Dell, Inc., 659 F.3d 1376 (Fed. Cir. 2011).
• Confirm the structure is clearly linked to the function, and that the disclosed algorithm covers the whole function. Note: A partial algorithm or restated function fails. Noah Systems, Inc. v. Intuit Inc., 675 F.3d 1302 (Fed. Cir. 2012). Commercial references can work if a skilled person would understand them, Gramm v. Deere & Co., No. 24-1598 (Fed. Cir. Mar. 11, 2026).
• Confirm you are not relying on the Katz exception beyond generic processing, receiving, and storing. EON Corp. IP Holdings LLC v. AT&T Mobility LLC, 785 F.3d 616 (Fed. Cir. 2015).
• If § 112(f) does not apply, run Phase 3 and Phase 4 across every way of achieving the result. Note: USPTO guidance says so too, 84 Fed. Reg. 57 (Jan. 7, 2019), and Sitrick v. Dreamworks, LLC, 516 F.3d 993 (Fed. Cir. 2008), is the classic application.
• For trained models, check that the specification discloses training data characteristics, architecture or features, the loss function, hyperparameter ranges, the validation method, and how any performance metric is defined and measured. Note: No precedential Federal Circuit decision we found applies Amgen squarely to a model claim, but performance-defined classes resemble Brita. See also Recentive Analytics, Inc. v. Fox Corp., 134 F.4th 1205 (Fed. Cir. 2025), on the § 101 side.
• Cross-check Section 101. Result-focused claims are exposed twice. Use the Patent Subject-Matter Eligibility After Alice: A Practical Checklist checklist.

Red flag: The only description of the claimed element repeats the claim, or a block diagram shows a labeled box. Fintiv called that a black box. An expert saying a programmer could write it will not fill the gap.

Phase 7: During prosecution

• Require a factor-based enablement rejection, and respond to the factors raised. 89 Fed. Reg. 1563.
• Argue claims separately where it matters. Otherwise the Board may select a representative claim. In re Starrett, No. 22-2209 (Fed. Cir. June 8, 2023) (nonprecedential).
• Address the full scope, not just some embodiments, and make every argument below, since unraised points are forfeited. In re PEN, No. 23-2282 (Fed. Cir. June 12, 2024) (nonprecedential).
• Support technical assertions with a declaration under 37 C.F.R. § 1.132. 37 C.F.R. Part 1.
• Explain each amendment that adds a term of degree or new word, and use it consistently. Infinity Computer Products, Inc. v. Oki Data Americas, Inc., 987 F.3d 1053 (Fed. Cir. 2021).
• Review obviousness arguments for statements about unpredictability that could undercut enablement.
• Decide whether to keep a continuation pending. Consider the two-year reissue window in 35 U.S.C. § 251. Note: For wider response practice, see Responding to a Patent Office Action: A Practical Checklist.

Red flag: A statement that "the art is highly unpredictable" appears in a response to a § 103 rejection, and the specification has few examples.

Phase 8: Before asserting a patent (patent owner)

• Chart the accused product against the claim, then chart the specification against the same reading. Note: Fed. R. Civ. P. 11 applies to the infringement theory, and a reading the specification cannot support invites a counterclaim and potentially a fee request under 35 U.S.C. § 285.
• Test your preferred construction against § 112(a). The drug moiety construction in Seagen and the jacketless construction in Liebel-Flarsheim won and then lost the case. Note: See Claim Construction Checklist: A Practical Checklist and Preparing for a Markman Hearing: A Practical Guide.
• Confirm the priority date you need with a full chart under Phase 4, and check the accused product's first public date.
• Interview inventors under privilege. Ask directly: "What did you have on the filing date?" and "When did you first see the accused feature?" Note: Inventor admissions were central in Seagen and Brita. Nuvo Pharmaceuticals (Ireland) Designated Activity Co. v. Dr. Reddy's Laboratories Inc., 923 F.3d 1368 (Fed. Cir. 2019).
• Collect later work by the inventors and the company bearing on hit rate or feasibility, and evaluate it before the other side does. Amgen Inc. v. Sanofi, Aventisub LLC, 872 F.3d 1367 (Fed. Cir. 2017).
• Review public statements on predictability and routine practice by the company and by your expert candidates.
• Select dependent claims with independent strength to assert alongside the independent.
• Retain a technical expert early, and ask for the honest Wands analysis first. Note: See Expert Witnesses After the 2023 Amendment to Rule 702: Daubert, Disclosure, and Cross-Examination.
• Assess the forum and exposure for post-grant challenge. 35 U.S.C. § 321, and see PTAB Post-Grant Checklist: A Practical Checklist.

Red flag: The infringement theory needs the claim to reach a technology the inventors have said they did not make and that the specification discourages.

Phase 9: After notice or suit (accused infringer or challenger)

• Calendar the contention deadline. Local patent rules often require § 112 grounds at the invalidity contention stage; check N.D. Cal. Patent L.R. 3-3, E.D. Tex. P.R. 3-3, or your court's equivalent.
• State the patent owner's necessary reading, and identify specific embodiments, including your own product, that fall within it. McRO.
• Decide how to reconcile noninfringement and invalidity, and plead in the alternative where needed.
• Check priority first. If the claim cannot reach the earliest date, run an anticipation analysis with intervening art, as in Seagen.
• Evaluate the forum. Post-grant review allows § 112 grounds within nine months of issue, 35 U.S.C. § 321; inter partes review does not, 35 U.S.C. § 311(b), except indirectly through priority. Regents of the University of Minnesota v. Gilead Sciences, Inc., 61 F.4th 1350 (Fed. Cir. 2023).
• Audit what you have said elsewhere. Your IPR petitions, FDA filings, and marketing may call the field routine. Note: Teva used Lilly's IPR statements against it. Consider this before any petition. See Filing or Defending an Inter Partes Review: A Practical Guide.
• Serve targeted discovery: inventor notebooks and failed experiments, prosecution counsel files as privilege allows, and post-filing development, under Fed. R. Civ. P. 26.
• Depose inventors on the filing-date state of their work, using the specification. See Deposition Conduct and Objection Checklist: A Practical Checklist.
• Retain an expert to quantify. Hit rates, time, and failures, tied to named embodiments. Fed. R. Evid. 702.
• If you want § 112(f) treatment, prepare to carry the burden with extrinsic evidence. TrackTime; Zeroclick, LLC v. Apple Inc., 891 F.3d 1003 (Fed. Cir. 2018).

Red flag: Your contention says only that the claims are "broad" or "functional." McRO reversed a summary judgment built on abstraction.

Phase 10: Through trial and appeal (both sides)

• Identify the burden and standard for each ground. Clear and convincing in court, Microsoft Corp. v. i4i Ltd. Partnership, 564 U.S. 91 (2011); preponderance at the Board.
• Tee up indefiniteness at claim construction, and request findings on extrinsic evidence. Teva Pharmaceuticals USA, Inc. v. Sandoz, Inc., 574 U.S. 318 (2015).
• Consider summary judgment if the facts of screening or disclosure are undisputed. Fed. R. Civ. P. 56; Baxalta.
• Move under Rule 50(a) on each § 112 ground, and renew under Rule 50(b). Fed. R. Civ. P. 50. Note: Wyeth, Seagen, and Teva each turned on JMOL. On enablement, facts go to the jury and the conclusion is law. Written description is a fact question.
• Draft special verdict questions that separate written description from enablement, and each claim from the others.
• Preserve each argument on the record. Satius reached enablement on appeal in unusual circumstances. Do not count on that.
• Monitor later history. Teva's certiorari window and any new Federal Circuit decisions may change the method-of-use analysis.

Red flag: Your expert testifies that a skilled person could make a "leap" from the specification to the claim. Stop and reconsider before that report is served, whichever side you are on.

This checklist is general information and not legal advice for a specific situation.

Related Documents

Related Articles

• Enablement, Written Description, and Indefiniteness After Amgen v. Sanofi: What Section 112 Demands: the doctrine and case readings behind each item.
• Claim Construction and Markman Hearings: How Courts Decide What a Patent Actually Covers: how construction fixes the scope you are testing.
• Provisional Patent Applications: What They Protect, What They Do Not, and How to Keep the Priority Date: why priority review starts at the first filing.
• Federal Subject-Matter Jurisdiction: Arising Under, Diversity, Supplemental Claims, and the Defect That Never Waives: where these disputes are heard, including the requirement that jurisdiction be right.

Related Guides

• Drafting Patent Claims and Specifications That Survive Section 112: A Practical Guide: how to fix what this checklist finds.
• Preparing for a Markman Hearing: A Practical Guide: making the definiteness record.
• Filing or Defending an Inter Partes Review: A Practical Guide: priority attacks and the risks of statements in a petition.

Related Checklists

• Claim Construction Checklist: A Practical Checklist: a companion review for construction positions.
• Preparing an Invention Disclosure: A Practical Checklist: the intake that makes Phase 1 easier.
• Responding to a Patent Office Action: A Practical Checklist: general prosecution steps.
• Prior Art Qualification Checklist: A Practical Checklist: what happens when priority fails.
• PTAB Post-Grant Checklist: A Practical Checklist: the Board route.
• Deposition Conduct and Objection Checklist: A Practical Checklist: conduct at inventor depositions.
• Patent Subject-Matter Eligibility After Alice: A Practical Checklist: the Section 101 cross-check.

Related Toolkits

• Section 112 Toolkit: Claim Support Charts, Invalidity Contentions, and Expert Declarations: worksheets and templates that implement these tasks.
• Provisional Application Toolkit: Invention Capture Templates, Written Description Audits, and Conversion Calendars: written description audits at the first filing.