Joint Patent Ownership

Each co-owner can practice the invention freely

Every joint owner may make, use, offer to sell, and sell the patented invention within the United States, and import it, without the consent of the other owners. A 1% co-owner has the same right to practice as a 99% co-owner — patent co-ownership has no concept of majority control.

→ Your co-owner can manufacture and sell the patented product in direct competition with you.

Each co-owner can license without consent — and keep the money

Under 35 U.S.C. § 262, each joint owner may license the patent to third parties without the consent of, and without accounting to, the other owners. 'Without accounting' means no duty to share licensing revenue.

→ Your co-owner can license your biggest competitor for $1 and owe you nothing. The competitor is then immune from your infringement suit.

All co-owners must join an infringement suit

A patent infringement action generally requires all co-owners as plaintiffs (Ethicon, Inc. v. United States Surgical Corp., Fed. Cir. 1998). A co-owner who refuses to join cannot ordinarily be forced to (absent a contractual obligation), and its refusal defeats standing.

→ One holdout co-owner gives every infringer a free pass — and an accused infringer can simply buy a license, or the ownership share, from your co-owner.

No partition by default — and the rules follow the patent

These defaults apply 'in the absence of any agreement to the contrary' (§ 262). They persist through assignments: whoever acquires a co-owner's interest acquires the same unilateral rights.

→ The problem compounds over time — a co-founder's share can end up with an acquirer, a creditor, or an estate you have never met.

Joint development without an agreement

Two companies collaborate on R&D; engineers from both contribute to the conception of an invention. Each employer ends up owning the contribution of its own inventors — making the companies joint owners of the resulting patent by default.

A co-inventor outside your company

A consultant, university professor, friend, or former colleague contributes to conception of even one claim. Inventorship attaches to claims — a person who conceived a single dependent claim is a co-inventor of the patent (Ethicon: the co-inventor of two claims out of 55 was a co-owner of the entire patent, and his retroactive license to the accused infringer ended the case).

Missing or defective invention assignment agreements

A founder or employee invents before signing an IP assignment agreement (or under an agreement that says 'will assign' instead of 'hereby assigns' — see Stanford v. Roche, U.S. 2011). The inventor personally retains rights, which can later land with a competitor or acquirer.

University and sponsored research entanglements

Research conducted with a university collaborator typically gives the university ownership of its employees' inventive contributions under its IP policy — putting the company and the university into co-ownership unless the sponsored research agreement says otherwise.

What does 35 U.S.C. § 262 say about joint patent ownership?

35 U.S.C. § 262 provides: 'In the absence of any agreement to the contrary, each of the joint owners of a patent may make, use, offer to sell, or sell the patented invention within the United States, or import the patented invention into the United States, without the consent of and without accounting to the other owners.' Unpacking the three critical phrases: (1) 'Without the consent of' — each co-owner can independently practice the invention and license third parties; no co-owner can veto another's exploitation. (2) 'Without accounting to' — a co-owner who earns licensing revenue or product profits owes the other co-owners nothing; there is no revenue sharing by default. (3) 'In the absence of any agreement to the contrary' — every default rule can be overridden by contract, which is why joint development agreements and co-ownership agreements are essential. Additional judicially-developed rules: all co-owners must voluntarily join as plaintiffs in an infringement suit (Ethicon, Inc. v. United States Surgical Corp., Fed. Cir. 1998) — a refusing co-owner generally cannot be involuntarily joined (limited exceptions include an exclusive licensee situation or a contractual obligation to join); and each co-owner's unilateral license fully immunizes the licensee from infringement claims by all co-owners. These rules differ sharply from real property co-ownership (where co-tenants owe accounting duties) and from copyright (where joint authors owe a duty to account for profits). Patent co-ownership is uniquely harsh — which is why practitioners treat undocumented joint ownership as a title defect.

Why is joint patent ownership considered a trap for startups?

Because the default rules convert what feels like a partnership asset into something either party can unilaterally devalue. The specific failure modes: (1) License-to-competitor risk: your co-owner can license the patent to your fiercest competitor without your consent, keep 100% of the fee, and there is nothing you can do — the competitor is fully immunized. An accused infringer's cheapest defense is often to buy a license (or the entire ownership share) from your co-owner. This is exactly what happened in Ethicon v. U.S. Surgical: an omitted co-inventor was added to the patent, granted U.S. Surgical a retroactive license, and Ethicon's infringement case collapsed. (2) Enforcement paralysis: all co-owners must join an infringement suit; a co-owner with different commercial interests (a university that doesn't want to sue an industry partner, a former collaborator who was acquired by the infringer's ally) can block all enforcement forever. (3) Diligence and financing damage: VCs and acquirers treat joint ownership without a co-ownership agreement as a material title defect — it can reduce valuation, trigger escrows and indemnities, or kill deals, because the asset cannot be exclusively controlled. (4) International complications: the US default (license without consent) is not universal — in many countries (e.g., the UK and France), a co-owner needs the others' consent to license. A multi-country portfolio with unmanaged co-ownership has different exploitation rules in every jurisdiction. The fix is always the same: allocate ownership and rights by contract before collaborating, and if joint ownership already exists, negotiate a co-ownership agreement covering licensing consent, revenue sharing, prosecution control, and enforcement cooperation.

How does someone accidentally become a co-owner of my patent?

Through the chain inventorship → ownership. The rules: (1) Patent rights initially vest in the inventors. Each named inventor presumptively owns an equal undivided interest in the entire patent — regardless of the size of their contribution. (2) Inventorship is determined claim by claim: anyone who contributed to the conception of even ONE claim is a co-inventor of the patent. In Ethicon v. U.S. Surgical (Fed. Cir. 1998), an electronics engineer who contributed to two claims of a 55-claim patent was a co-inventor — and therefore a co-owner of the entire patent, entitled to license the accused infringer retroactively. (3) Ownership leaves the inventor only by written assignment. If a contributor never signed an assignment to your company, they personally own their share. Common accidental-co-owner scenarios: a consultant or contractor who brainstormed the solution with your team but signed no IP assignment; a university professor whose contribution belongs to the university under its IP policy; an engineer at a partner company during an informal collaboration; a co-founder who invented before the company existed and never assigned the rights afterward; an employee whose offer letter promised to assign ('will assign') but never executed a present-tense assignment — under Board of Trustees of Stanford University v. Roche Molecular Systems (U.S. 2011), 'agree to assign' is a mere promise that can be defeated by a later 'hereby assign' to someone else. Prevention: present-tense assignment agreements from every employee, founder, and contractor before inventive work; clear IP terms in every collaboration, consulting, and sponsored research agreement; and careful, legally-grounded inventorship determinations when filing.

Can co-owners of a patent sue each other for infringement?

No. A co-owner cannot infringe its own patent — each joint owner holds the full statutory right under 35 U.S.C. § 262 to make, use, sell, and import the invention. Practicing the invention is the exercise of an ownership right, not infringement. Consequences: (1) Co-owners cannot use infringement law against each other no matter how lopsided the commercial outcome — if your co-owner builds a billion-dollar business on the patent while you build nothing, your remedy is nothing (absent a contract). (2) A co-owner's licensees are equally immune: a license from any single co-owner is a complete defense against all co-owners. (3) Claims between co-owners must sound in contract (breach of a co-ownership or joint development agreement), or occasionally in state-law theories like breach of fiduciary duty where a special relationship exists (partners, trustees) — patent law itself provides no inter-owner remedy. What co-owners CAN do by contract: divide fields of use exclusively (co-owner A takes medical applications, co-owner B takes industrial); require consent for licensing; share royalties; allocate prosecution and maintenance costs; and commit to join enforcement actions. Courts enforce these agreements like any other contract — § 262 expressly defers to 'any agreement to the contrary.' This is why the universal advice from patent counsel is: never leave co-ownership on the statutory defaults.

Is joint patent ownership treated the same in other countries?

No — and the differences are large enough to change exploitation strategy country by country. United States: each co-owner can practice AND license unilaterally, with no duty to account (35 U.S.C. § 262). United Kingdom: under the Patents Act 1977 (§ 36), each co-owner may practice the invention itself without consent, but may NOT grant licenses, assign its share, or mortgage it without the consent of all other co-owners — nearly the opposite of the US licensing rule. France: co-ownership is governed by the Intellectual Property Code (Art. L613-29 et seq.): each co-owner can exploit the invention personally (with compensation owed to non-exploiting co-owners in some circumstances) and can grant non-exclusive licenses only after notifying co-owners, who have a right of objection/preemption; exclusive licenses require unanimous agreement. Germany: co-ownership follows the civil law of community by fractional shares (Bruchteilsgemeinschaft); each co-owner can use the invention itself, but licensing generally requires the consent of all co-owners, and the financial allocation of one owner's own use is a recurring source of litigation. Japan: under the Patent Act (Art. 73), each co-owner may practice the invention itself, but assignment of a share, licensing, and creating security interests all require the consent of all co-owners. China: similar structure — a co-owner may exploit the patent itself and grant ordinary (non-exclusive) licenses with royalties shared among co-owners, but assignment or exclusive licensing requires agreement of all co-owners. Practical consequence: a US-drafted joint development agreement that simply mirrors § 262 defaults does not produce the same outcomes abroad. International collaborations need choice-of-law and country-by-country exploitation terms, or the same patent family will carry different co-ownership rights in every major market.