Co-Inventor Agreements: What They Are and Why You Need One

Inventing with others is common. A colleague contributes a key insight. An engineer solves a critical problem. A business partner brings the idea to life. In each case, the question of who owns what can become one of the most contentious issues in the life of a patent — and one of the easiest to prevent with a well-drafted agreement signed before work begins.

Co-inventor disputes have destroyed partnerships, invalidated patents, and derailed commercialisation deals that were within reach. A co-inventor agreement costs very little to prepare. The litigation it prevents can cost millions.

What Is a Co-Inventor?

A co-inventor — also called a joint inventor — is a person who contributed to the conception of at least one claim in the patent. This is a legal definition, not an intuitive one, and it catches many inventors by surprise.

Who is a co-inventor:

• A person who conceived of a key element that became part of a patent claim
• A person who solved a specific technical problem in a way that shaped the invention
• A person who suggested a novel combination of known elements that was incorporated into the claims

Who is NOT a co-inventor:

• A person who built the prototype according to your instructions (without contributing conceptually)
• A person who provided funding or resources
• A person who supervised the work but did not contribute to the inventive concepts
• A person who performed routine experiments or testing
• A person whose idea was tried but did not work and was not incorporated

The distinction matters enormously. In most jurisdictions, incorrectly naming (or failing to name) inventors on a patent application is a serious error that can invalidate the patent — either immediately or in later legal proceedings.

Why Joint Ownership Is Complicated

In most jurisdictions, each joint owner of a patent has independent rights to use, license, or exploit the patent without the consent of the other joint owners — and without sharing the proceeds.

This creates a significant problem if co-inventors have not agreed otherwise. Consider:

• Co-inventor A and Co-inventor B file a patent together
• Co-inventor B independently licenses the patent to a competitor for a lump sum payment
• Co-inventor A receives nothing — and has no legal recourse under default joint ownership rules

This is not a hypothetical edge case. It happens regularly, particularly when collaborations dissolve acrimoniously or when one party unexpectedly finds a licensing opportunity.

The rules on joint ownership vary by jurisdiction — but they are problematic almost everywhere:

United States: Each joint owner may independently exploit the patent — including licensing to anyone, for any amount — without consent from or accounting to other joint owners. This is one of the most extreme versions of the rule globally.

United Kingdom: Similar to the US — each co-owner may work the patent themselves but may not license it to others without the consent of all co-owners. Slightly more protective than the US position.

Germany: Each co-owner may use the patent themselves but cannot grant licences or assign their share without all co-owners' consent.

France: Co-owners cannot license or assign without consent of all other co-owners, but any co-owner can bring an infringement action independently.

China: Co-owners can each exploit the patent personally but cannot license or assign without consent of other co-owners. Exploitation proceeds do not need to be shared unless agreed.

Japan: Similar to China and Germany — personal exploitation is permitted without consent; licensing and assignment require consent from all co-owners.

South Korea: Co-owners may exploit personally without consent; licensing requires consent of all co-owners; assignment of a share requires consent of all co-owners.

Australia: Each co-owner may exploit the patent without consent of others and without accounting for profits. Similar to the US position.

India: Similar to the UK — exploitation permitted without consent; licensing requires all co-owners' consent.

GCC (Qatar, UAE, Saudi Arabia): GCC and national patent laws in the Gulf generally follow a model where co-owners can exploit personally but require consent for licensing and assignment. Qatar's patent law provides that joint ownership rights are governed by agreement between the parties, with statutory defaults applying in the absence of agreement.

The practical conclusion is the same in every jurisdiction: default joint ownership rules create risks and ambiguities that can seriously damage the commercial value of a patent. A co-inventor agreement — drafted before any work begins — overrides these defaults and creates the rules that actually govern the relationship.

What Happens Without an Agreement: A Cautionary Scenario

Two engineers — one in Doha, one in Munich — collaborate on a new desalination membrane design. They agree informally to "split things 50/50" and file a joint US patent application. The patent grants. Then:

The Munich engineer, without consulting his co-inventor, grants a non-exclusive license to a German water treatment company for €200,000. Under US patent law (where the patent was granted), he has every right to do this — and keep every cent. He does not need his co-inventor's permission, and he does not owe him a share of the proceeds.

The Doha engineer discovers this when the German company starts selling products based on his invention. He is furious. But he has no legal recourse — they never signed an agreement, and the default US rule allows exactly what happened.

Had they signed a co-inventor agreement before filing, the agreement could have required mutual consent for all licensing, 50/50 revenue sharing on any deal, and designated one party as the "licensing lead" with authority to negotiate on behalf of both. A $500 agreement would have prevented a €200,000 dispute.

This is not a rare scenario. It happens every time collaborators assume shared goodwill is a substitute for a written agreement.

What a Co-Inventor Agreement Should Cover

A well-drafted co-inventor agreement addresses six core areas:

1. Identification of the Parties and Their Contributions

Clearly identify each inventor and, as specifically as possible, describe the nature of their expected contribution. This does not need to be a precise technical specification — but it should distinguish who is contributing what at a conceptual level.

This section is useful if a dispute arises about whether someone's contribution was genuinely inventive — and therefore whether they are correctly named as a co-inventor.

2. Ownership Percentages

The default in most jurisdictions is equal ownership regardless of the relative size of each party's contribution. Equal ownership is often not what the parties actually intend. A lead inventor who conceived the core invention and invited a collaborator to solve a specific sub-problem may not intend to share 50/50.

The agreement should specify each party's ownership percentage and the basis for that allocation. Ownership can be split any way the parties agree — 70/30, 60/20/20, or any other division. What it cannot do is leave the question unresolved.

3. Decision-Making: Licensing and Assignment

One of the most important provisions. The agreement should specify:

• Whether licensing decisions require unanimous consent, majority vote, or can be made by one party
• What happens if the parties cannot agree on whether to license
• Whether any party has a right of first refusal if another party wants to sell their share
• Minimum acceptable royalty rates or deal terms (optional but useful)
• How licensing proceeds are divided among co-owners

This section prevents the scenario where one co-owner unilaterally licenses the patent to a third party — or, conversely, where one co-owner's obstruction prevents the patent from being commercialised at all.

4. Prosecution Responsibilities and Cost Sharing

Filing, prosecuting, and maintaining a patent costs money. The agreement should specify:

• Who is responsible for managing the patent application and prosecution (typically the lead inventor or an agreed attorney)
• How prosecution costs are shared among co-owners
• What happens if one co-owner cannot or refuses to pay their share of costs — does their ownership percentage reduce? Do others have the right to buy out their share?
• Who is responsible for maintenance fee payments, and how those costs are shared
• What happens if the patent lapses because one party fails to contribute to maintenance costs

5. Enforcement

If the patent is infringed, the agreement should address:

• Whether all co-owners must consent to bring an infringement action
• How enforcement costs are shared
• How damages and settlements are divided
• What happens if one co-owner wants to pursue infringers but others do not

In jurisdictions where any co-owner can independently bring an infringement action (such as France and some US states for their own exploitation), this provision is especially important.

6. Exit and Dispute Resolution

Collaborations end. The agreement should address what happens when they do:

• Can a co-owner sell or transfer their share? To whom? Under what conditions?
• Do other co-owners have a right of first refusal on any transferred share?
• What happens if a co-owner dies or becomes insolvent?
• What is the dispute resolution mechanism — mediation, arbitration, or litigation?
• Which country's law governs the agreement?

The governing law question is particularly important for international collaborations. The law of the country where the patent is filed does not automatically govern the co-owner agreement — the parties should specify this explicitly.

Co-Inventor Agreement vs. Assignment Agreement

A co-inventor agreement governs the relationship between co-inventors who each retain an ownership interest. It is different from an assignment agreement, in which one inventor assigns (transfers) their ownership interest to another party entirely.

Assignment is appropriate when:

• An employee invents something in the course of employment and the employer owns the resulting IP by contract or statute
• A contractor or consultant is engaged to develop a specific invention, and ownership is intended to vest in the commissioning party
• One co-inventor wishes to exit the arrangement and sell their share to the other

Many employment contracts and contractor agreements include IP assignment clauses — often in the fine print. If you are collaborating with someone who is employed elsewhere, their employment contract may automatically assign to their employer any invention they contribute to. This is a common and serious surprise in co-inventor situations. Always clarify IP ownership obligations before beginning any collaboration.

The Contractor and Consultant Problem

One of the most common co-inventor pitfalls occurs when inventors hire contractors — engineers, designers, chemists — to help develop their invention. If the contractor contributes to the conception of a patentable claim, they may be a co-inventor. If they are a co-inventor with no assignment agreement in place, they own part of the patent.

Prevent this by:

1. Including an IP assignment clause in every contractor agreement — before work begins. The contractor agrees that any inventions developed in the course of the engagement are assigned to the commissioning party.

1. Being specific about scope — what work is covered, what inventions may result, and what is assigned.

1. Obtaining a signed assignment upon completion of the engagement, if any inventions resulted from the work.

This applies globally — in the US, UK, Germany, China, Japan, South Korea, Australia, India, and throughout the GCC. The specific statutory treatment of contractor IP varies, but in most jurisdictions the default is that a contractor owns what they create unless there is a clear contractual agreement to the contrary.

Download our template: IP Assignment Agreement for Contractors

University and Employer Complications

If any co-inventor is affiliated with a university or employer, that institution may have an ownership claim in the invention. Most universities and many large employers have IP policies that assign to the institution any invention made using its resources, in the course of employment, or related to its research activities.

Before filing a patent with a university researcher as a co-inventor, confirm:

• Does the university's IP policy cover this invention?
• Does the university need to be named as an assignee or co-owner?
• Does the university's tech transfer office need to be involved in the filing?

This applies globally. In the US, the Bayh-Dole Act governs federally funded research IP. In the UK, universities follow AURIL guidelines. In China, universities are required to register IP created with public research funding. In Japan, the 2004 University Reforms encouraged universities to own IP from research activities. In many GCC countries, IP created using government or university funding is subject to specific ownership rules under national IP laws.

Ignoring university IP rights can invalidate a patent if the university challenges inventorship or ownership after grant.

Key Clauses to Include

The following clauses are essential in any co-inventor agreement. Download our full template: Co-Inventor Agreement Template

Recitals: Brief description of the collaboration and what the parties intend to develop.

Definitions: Clear definitions of "Invention," "Patent," "Net Proceeds," and other key terms.

Ownership: Specific percentages for each party.

Prosecution and maintenance: Who manages the patent and how costs are shared.

Licensing: Decision-making process, consent requirements, proceeds division.

Enforcement: Who can sue, how costs are shared, how recoveries are divided.

Assignment and transfer: Right of first refusal, permitted transferees, restrictions on transfer.

Confidentiality: Obligations of each party regarding the invention during and after the collaboration.

Term and termination: How long the agreement lasts and what happens when it ends.

Governing law and dispute resolution: Which jurisdiction's law applies and how disputes are resolved.

Entire agreement: Confirms this document supersedes any prior discussions or informal arrangements.

What to Do If You Have Already Filed Without an Agreement

If you have already filed a patent with co-inventors and no agreement is in place, it is not too late — but act promptly.

1. Document the existing understanding — if all parties have an informal shared understanding about ownership and licensing, document it now in writing.

1. Execute a joint ownership agreement — covering the key provisions above, even after filing. The agreement governs the parties' relationship going forward regardless of when it is signed.

1. Review inventorship — confirm that all named inventors genuinely contributed to at least one patent claim. Incorrect inventorship is correctable in most jurisdictions (in the US, for example, the USPTO allows correction of inventorship under 35 USC §256), but it must be corrected before the error becomes a problem in litigation.

1. Consult a patent attorney — if there is any dispute or ambiguity about inventorship or ownership, get legal advice before it escalates.

Sources

1. USPTO - Inventorship — US rules on joint inventorship and correction of inventorship under 35 U.S.C. section 256
2. 35 U.S.C. - Patent Law — US statutes on joint ownership (section 262) and inventorship requirements
3. European Patent Convention (EPC) — European rules on inventor designation and rights of joint applicants
4. WIPO - Joint Ownership of IP — International perspective on co-ownership of patent rights across jurisdictions