Claim charts are tables that place each element of a patent claim beside the evidence that matches it, with a citation for every match. The evidence is a product in an evidence of use (EoU) chart, an earlier publication in an invalidity chart, and a technical standard in a standard essential patent (SEP) chart.
The method for product evidence is described on the page on evidence of use claim charts.
What claim charts contain
A chart splits a claim into its elements, one row for each clause, and gives each row its evidence and a precise citation. Most charts include:
- the patent number, the claim and its effective filing date;
- the claim text, split into labelled elements;
- the evidence for each element, quoted or shown as an image or screenshot;
- a source and a date for each item of evidence;
- a comment where the match is partial or depends on how a term is read.
Literal infringement requires every element of a claim, so one empty row defeats the chart unless the doctrine of equivalents or another argument covers the gap.
Claim charts side by side
| Aspect | Evidence of use chart | Invalidity chart | SEP chart |
|---|---|---|---|
| Claim compared with | A product or process | Earlier publications | A technical standard |
| Question answered | Whether the product has every element | Whether the elements were disclosed or obvious | Whether the standard requires the claim |
| Main evidence | Manuals, datasheets, teardowns | Patents, articles, brochures | Technical specifications |
| Typical use | Licensing, infringement contentions | Invalidity contentions, inter partes review | Licensing, litigation |
Evidence of use charts
An evidence of use chart, also called an infringement claim chart, maps a claim onto a product sold by another company. The evidence must be public or lawfully obtained, and when the feature sits inside the product, a reverse engineering study may be needed.
When a US complaint is filed, Rule 11 of the Federal Rules of Civil Procedure treats counsel as certifying, after a reasonable inquiry, that its factual contentions have evidentiary support. A claim chart is a common way to document that pre-suit inquiry.
After suit, Patent L.R. 3-1(c) of the Northern District of California Patent Local Rules requires a chart showing where and how each limitation of each asserted claim is found. The post on invalidity contentions and Rule 11 claim charts compares these filings.
Invalidity claim charts
An invalidity claim chart maps the claim elements onto prior art. Each reference must qualify as prior art, which generally means it was public before the effective filing date. A single reference that discloses every element supports anticipation under 35 U.S.C. 102. Where the elements are spread across several references, the comment explains the reason to combine them, which supports obviousness under 35 U.S.C. 103.
In the Northern District of California, invalidity contentions are due within 45 days of service of the infringement contentions. Patent L.R. 3-3(c) requires them to include a chart for each item of prior art, under the rules as checked in October 2026. The art usually comes from a patent invalidity search, often by the team that prepares the invalidity contention claim charts.
SEP claim charts
A SEP chart maps a claim onto the text of a technical standard rather than a product. The intellectual property rights policy of the European Telecommunications Standards Institute (ETSI) sets the test. A patent is essential when, on technical rather than commercial grounds, compliant equipment or methods cannot be made, sold or used without infringing it.
For each element, the chart cites the clause of the specification that requires it, such as a section of a mobile network specification. Some features of a standard are optional, so a second step shows that real products implement the clause, as described on the page on SEP claim charts.
Strong and weak mapping
Reviewing attorneys usually look for these signs of a weak mapping:
- the evidence uses different words, and the chart assumes they mean the same;
- the citation points to a whole document rather than a page or figure;
- the evidence is undated, or too late to count as prior art;
- an element is met only by an optional feature or one product variant.
A good chart flags these rows to show where more searching, a teardown or a claim construction argument is needed.
What drives the cost
Charts are usually priced per chart, one patent against one product, reference or standard. The price rises with the number and length of the claims, translation, teardowns and short deadlines.
Commission claim charts
We prepare evidence of use, invalidity and SEP claim charts for law firms and licensing teams. Send us the patent and the target product or prior art through our evidence of use claim chart service.
This guide is general information and is not legal advice.
Frequently Asked Questions
What is a claim chart in patent law?
A claim chart is a table that compares each element of a patent claim with evidence, such as a product, a prior art reference or a technical standard. Each row cites where the element is found, so the chart tests infringement, validity or essentiality claim by claim.
Who prepares claim charts?
Patent attorneys, technical experts and specialist search firms prepare claim charts. A search firm usually finds the evidence and drafts the mapping, while the attorney reviews it, decides how disputed terms are read and signs anything filed with a court.
How many claims go into an evidence of use chart?
Most evidence of use charts start with the independent claims, because a product that lacks an element of an independent claim cannot literally infringe its dependent claims. Dependent claims are added when they are likely to be asserted, or as a fallback position.
Does a SEP claim chart prove that a patent is essential?
No. A SEP chart is an argument for essentiality, not a finding. A court decides it, or the parties agree it, and ETSI does not assess it. A chart is stronger when it maps a mandatory part of the standard and shows that products implement it.
How long does it take to prepare a claim chart?
It varies with the length of the claims, how easily the evidence is found and how many charts are needed. A chart built from public documents is quicker than one that needs teardown results or translated references, so delivery dates are agreed case by case.