An invalidity claim chart is a table that sets each limitation of a patent claim beside the passage of a prior art reference that discloses it. Each row quotes the reference, gives its exact location and explains the match, so the invalidity argument can be tested one limitation at a time.
Charts support invalidity contentions in US district courts, inter partes review (IPR) petitions and validity opinions. The search that comes first is described in the guide to the patent invalidity search process and cost.
What an invalidity claim chart contains
A common layout uses one row per claim limitation and 4 columns: the limitation, the quoted disclosure, its location and a comment on the match, often with a grade.
Patent Local Rule 3-3(c) of the Northern District of California requires a chart showing where and how each limitation is found in each item of prior art.
Anticipation charts and obviousness charts
An anticipation chart under 35 United States Code (U.S.C.) 102 relies on one reference. Under section 2131 of the Manual of Patent Examining Procedure, every element must be found in that reference, expressly or inherently, and arranged as the claim requires.
An obviousness chart under 35 U.S.C. 103 often combines 2 or more references. It also needs articulated reasoning with a rational underpinning, a standard the Supreme Court approved in KSR International v. Teleflex in 2007. A primary reference usually covers most rows, and a secondary reference supplies the missing limitation.
How to build an invalidity claim chart in 6 steps
The references normally come from a patent invalidity search that has already ranked the strongest art, and the chart is built in this order:
- The claim is split into labelled limitations, one clause or wherein condition per row.
- Each reference is checked as prior art, and its effective prior-art date is recorded.
- The passage is quoted with its column and line, paragraph number or figure.
- The claim mapping is explained, including why different wording describes the same feature.
- The claim construction that each row relies on is noted.
- Each row is graded as strong, partial or weak.
In many US district courts, disputed terms are construed after invalidity contentions are served, so a construction order can turn a strong row into a weak one. A chart that records the reading behind each row can be re-checked rather than rebuilt.
Worked example: an invalidity claim chart for an invented claim
The example below is an illustration and does not describe a real project. The claim and both references are invented.
Claim 1 of a fictional patent covers a drinks bottle. Its limitations are [1a] a container body, [1b] a removable lid, [1c] a temperature sensor in the lid and [1d] a lid display showing the liquid temperature. Reference A is an earlier patent publication on an insulated flask.
| Limitation | Reference A disclosure | Location | Grade |
|---|---|---|---|
| [1a] Container body | A double-walled steel vessel | Para. [0012], Fig. 1 | Strong |
| [1b] Removable lid | A screw cap threaded onto the neck | Para. [0014], Fig. 2 | Strong |
| [1c] Sensor in the lid | A thermistor mounted inside the cap | Para. [0018], Fig. 3 | Strong |
| [1d] Temperature display | A warning light that turns red above 60 °C | Para. [0020] | Weak |
Row [1d] is a weak mapping because a red light shows that a threshold has been passed, not the temperature itself. Whether it meets the claim depends on how the display term is construed.
Reference B, a journal article, discloses a cap with a numeric readout of liquid temperature. An obviousness chart therefore combines A with B for [1d], and its comment explains why a skilled person would have replaced the warning light with a numeric display.
Adapting the prior art chart to the forum
- District court contentions: any qualifying prior art can be charted, including products on sale or in public use. In the Northern District of California, invalidity contentions are due 45 days after service of the infringement contentions.
- IPR petitions: grounds are limited to sections 102 and 103, based only on patents or printed publications (35 U.S.C. 311(b)). Under 37 Code of Federal Regulations (CFR) 42.104(b)(4), the petition must specify where each claim element is found in those documents.
A chart built on a product teardown therefore needs a printed publication showing the same features before it can support an IPR ground. Contentions and Federal Rule of Civil Procedure 11 charts are compared in this guide to invalidity contentions, and other chart types in claim charts explained.
Invalidity claim chart support
We prepare invalidity claim charts from a supplied list of references or from our own invalidity search. Send the patent and the references through our invalidity contention claim chart service.
This guide is general information and is not legal advice.
Frequently Asked Questions
What is the difference between an invalidity claim chart and an infringement claim chart?
An invalidity claim chart compares a claim with prior art to show that it was not new or was obvious. An infringement chart compares the claim with an accused product to show that the product is covered. The rows look alike, but the evidence and the dates differ.
Should each prior art reference get its own invalidity chart?
Usually, yes. Many practitioners keep one chart per reference and add separate combination charts for obviousness. A reference that fails on one row is then visible on its own, and it can be dropped or replaced without the other charts being rebuilt.
Should dependent claims be charted for invalidity?
Yes, when they are asserted or likely to be. A dependent claim adds limitations, so a reference that anticipates the independent claim may still miss the dependent one. Charting them early shows the fallback positions of the patent owner and where more searching is needed.
How much does an invalidity search cost before charting?
Synoptic IP prices an invalidity search at USD 1,200–10,000, with delivery in 1–3 weeks (checked October 2026). The cost within that range depends on the technology, the number of claims, the languages covered and the depth of the non-patent literature search.
Who is responsible for the content of an invalidity claim chart?
The attorney who signs and serves or files the chart is accountable for its content. A search firm or technical analyst can find references and draft the mapping. The attorney chooses the invalidity theories, settles the claim construction positions and signs the contentions or petition.