Inventorship is a legal question about who conceived the claimed invention. It is not a question about who worked hardest, who ran the project, or who deserves credit — and treating it as a matter of courtesy is how patents become vulnerable.
Getting it wrong has consequences. Incorrect inventorship can render a patent invalid or unenforceable, and an omitted inventor who never assigned their rights may hold an undivided interest in the whole thing.
The test: conception
An inventor is someone who contributed to the conception of at least one claim.
Conception is the formation in the mind of a definite and permanent idea of the complete and operative invention, as it is thereafter to be applied in practice. The invention must be sufficiently developed that a skilled person could reduce it to practice without extensive further experimentation.
| Contribution | Inventor? |
|---|---|
| Conceived the claimed solution | Yes |
| Conceived one element of one claim | Yes |
| Suggested the problem to be solved | No |
| Built a prototype to someone else's design | No |
| Ran experiments under direction | No |
| Supervised the project | No |
| Provided funding or resources | No |
| Reduced the invention to practice, having been told how | No |
Reduction to practice is not conception. The engineer who built the working model from a design handed to them contributed real work and is not an inventor. This is counterintuitive to almost everyone outside patent practice and is the source of most inventorship disputes.
Contributing to one claim is enough. A co-inventor need not have contributed to every claim, or worked at the same time as the others, or contributed equally.
Conception must be of the claimed invention. Someone who conceived an idea that was never claimed is not an inventor of the patent as granted.
Inventorship is determined by the claims — which change
This is the part most often missed.
Inventorship is assessed against the claims as finally allowed, not as filed. Claims are routinely cancelled, narrowed and amended during prosecution, and each change can alter who the inventors are.
A worked sequence:
| Stage | Claims | Correct inventors |
|---|---|---|
| Filing | Claims 1-20, covering methods A, B and C | Smith, Jones, Patel |
| First office action | Claims 8-14 (method B) cancelled | Under review |
| Allowance | Claims 1-7 and 15-20 (methods A and C) | Smith and Patel only |
Jones conceived method B and nothing else. With those claims gone, Jones is no longer an inventor and should be removed before issue.
Nobody reviews this. Inventorship is set at filing, the declaration is executed, and the question is never revisited even though the claims that define it have changed substantially. It is worth a ten-minute check at allowance on every application.
Inventorship is not ownership
Two separate questions that get conflated constantly.
| Inventorship | Ownership | |
|---|---|---|
| Question | Who conceived it? | Who holds title? |
| Determined by | The claims and the facts of conception | Assignment documents and employment agreements |
| Changeable | Only by correction | Freely, by assignment |
| Appears on the patent | Yes, as named inventors | As assignee, if recorded |
Inventors own their inventions initially. In the absence of any agreement, each named inventor holds title.
Most assign to an employer. Employment agreements typically include a present-tense obligation to assign, and clean title matters when a patent is sold, and the assignment is executed and recorded during prosecution. A patent commonly has three named inventors and one owner.
The danger is an unassigned inventor. If someone should have been named and was not, and they never signed an assignment, they may hold an undivided interest in the patent — and can license it to your competitor without asking anyone.
Co-ownership: the rule that surprises people
Under 35 U.S.C. 262, absent any agreement, each co-owner may make, use, offer to sell, sell or import the patented invention — and license others to do so — without the consent of the other owners and without accounting to them.
Read that again, because the consequences are severe.
| Situation | Consequence |
|---|---|
| One co-owner grants a non-exclusive licence | Valid, no consent needed, no revenue shared |
| One co-owner refuses to join a suit | Generally the suit cannot proceed |
| One co-owner sells their interest | Buyer becomes a co-owner with full rights |
| Co-owners disagree on enforcement | No mechanism to compel |
One co-owner can destroy the patent's value unilaterally. A licence granted to the very company you intended to sue is entirely lawful and cannot be undone.
Enforcement requires all of them. A patentee generally cannot sue without joining every co-owner, and a co-owner who declines to join can block the action entirely.
Which is why co-inventors should have a written agreement, and why it should be signed early — before there is anything worth arguing about. A short document addressing licensing consent, revenue sharing and enforcement decisions prevents the disputes that are otherwise close to inevitable.
Correcting inventorship
Errors are common and the law expects them. Correction is available for both pending applications and granted patents, provided the error arose without deceptive intent.
Pending applications — 37 CFR 1.48
File a request with a corrected application data sheet naming the correct inventors, plus the fee. Where an inventor is being added, an oath or declaration from that person is required.
Straightforward while the application is pending, which is another argument for reviewing inventorship at allowance rather than after grant.
Granted patents — 35 U.S.C. 256
File a request to correct inventorship with a statement from each person being added or removed, agreement from the current inventors and any assignee, and the fee. The Office issues a certificate of correction.
Or by court order. Where the parties do not agree, a district court may order correction under 256, and this is how contested inventorship disputes are usually resolved.
The deceptive intent requirement. Correction is available where the error arose without deceptive intent. Deliberate misnaming is a different matter and can support an inequitable conduct defence that renders the whole patent unenforceable.
Why it matters in litigation
Incorrect inventorship is a standard defence, raised routinely because it is cheap to plead and occasionally devastating.
The strongest version is the omitted inventor who never assigned, which surfaces in patent infringement defence work more often than it should. If the defence can show that someone contributed to conception, was not named, and never assigned their rights, that person may hold an interest in the patent. A licence from them defeats the infringement claim entirely.
Defendants look for this in employment records, lab notebooks and email. The question is who first articulated the claimed solution, and contemporaneous documents answer it better than recollection years later.
Correction is available even during litigation, which limits the damage. But the process is disruptive, and where deceptive intent can be shown the exposure is unenforceability rather than a correctable error.
A worked example: the courtesy naming
A company files an application on a control algorithm. Four people are named:
| Person | Role | Actual contribution |
|---|---|---|
| Chen | Research engineer | Conceived the algorithm |
| Okafor | Research engineer | Conceived the error-correction step, claim 7 |
| Reyes | Test engineer | Built and ran the test rig to specification |
| Lindqvist | Department head | Approved the project, reviewed results |
Chen and Okafor are inventors. Chen conceived the core; Okafor conceived a claimed element.
Reyes is not, despite doing substantial work. Building to a specification is reduction to practice, not conception.
Lindqvist is not, and naming a department head as a matter of courtesy is a recognisable and risky practice.
What happens next
During prosecution, claim 7 is cancelled to overcome prior art. Okafor's only contribution goes with it, and inventorship should be corrected to Chen alone before issue. It is not.
Three years later the patent is asserted. The defendant deposes all four named inventors. Reyes and Lindqvist both testify accurately that they did not conceive anything claimed, and Okafor confirms their contribution was the cancelled claim.
The defence now has an inventorship attack on a patent naming three non-inventors. It is correctable under 256 — the error was not deceptive — but correction happens mid-litigation, costs money, and hands the defendant a narrative about how carefully the patent was prepared.
Ten minutes at allowance would have prevented all of it.
AI and inventorship
Current US law requires a natural person. The Federal Circuit held in Thaler v. Vidal (2022) that an inventor under the Patent Act must be a human being, and an AI system cannot be named.
AI-assisted inventions remain patentable. USPTO guidance takes the position that inventions made with AI assistance are eligible provided a natural person made a significant contribution to the conception. The person who directed the system, framed the problem, or recognised and developed the output may qualify; merely running a tool and accepting its output may not.
This is an actively developing area. The guidance is recent, the case law is thin, and the practical question of how much human contribution is enough has not been settled. Applications relying substantially on AI-generated output should document the human contribution to conception contemporaneously, because reconstructing it later is considerably harder.
Before filing, and again at allowance
- Identify who conceived each claim, not who worked on the project.
- Exclude those who only reduced to practice, supervised, or funded.
- Do not name anyone as a courtesy — it creates a defence for someone else to use.
- Confirm every named inventor has assigned their rights.
- Review inventorship again at allowance, because the claims have changed.
- Correct promptly under 37 CFR 1.48 while pending, or 35 U.S.C. 256 after grant.
- Get a written agreement between co-inventors on licensing, revenue and enforcement.
- Document conception contemporaneously, particularly where AI tools were involved.