What is the difference between an assignee and a licensee in patent law?

Under U.S. patent law, there are two principal mechanisms for transferring rights in a patent to a third party: assignment and license. The two look superficially similar (both allow someone other than the original inventor to benefit from a patent) but they differ in a foundational way. An assignment transfers ownership. A license transfers permission. That distinction has consequences at every stage of the patent lifecycle, from who can file the application to who can sue an infringer.

A U.S. patent grants the patentee the right to exclude others from making, using, offering for sale, or selling the invention throughout the United States, or importing the invention into the United States. Deciding whether to assign or license is a decision about how much of that exclusionary right to hand over, and on what terms.

The assignee: a successor in title

Under 35 U.S.C. § 261, patents shall have the attributes of personal property. Because a patent is personal property, it can be sold, mortgaged, and inherited in the same way as other assets. An assignment is precisely that kind of transfer.

An assignment of a patent is the transfer to another party of all or part of the assignor's right, title, and interest in the patent or patent application. An assignment must transfer the entire ownership interest or a defined percentage of that ownership interest, together with all rights inherent in that share. If the transfer carves out some rights while retaining others (for example, field-of-use or geography), it is a license, not an assignment.

The legal consequence of an assignment is that the assignee steps into the shoes of the original patentee. Under 35 U.S.C. § 100(d), the term "patentee" includes not only the patentee to whom the patent was issued but also the successors in title to the patentee. An assignee is a successor in title and therefore becomes the statutory patentee upon assignment. Under 35 U.S.C. § 281, a patentee shall have remedy by civil action for infringement of the patent. The assignee holds this right directly and can bring an infringement suit in its own name without joining the original inventor.

An assignee can also file a patent application before the patent issues. Under 37 CFR § 1.46, a person to whom the inventor has assigned or is under an obligation to assign the invention may file a patent application as the applicant. Once the application matures, the patent can issue in the assignee's name. Under 35 U.S.C. § 152, patents may be granted to the assignee of the inventor of record in the Patent and Trademark Office. This is the standard arrangement in most employment contexts, where inventions vest in the employer-assignee and the employer prosecutes the application.

Recording is critical to protect the assignee's title. Under 35 U.S.C. § 261, an assignment is void against any subsequent purchaser or mortgagee who lacks notice unless the assignment is recorded in the Patent and Trademark Office. An assignee who delays recording risks losing priority to a later bona fide purchaser who records first.

The licensee: a permitted user, not an owner

A patent license is a contractual agreement that the patent owner will not sue the licensee for patent infringement if the licensee makes, uses, offers for sale, sells, or imports the claimed invention, as long as the licensee fulfills its obligations and operates within the bounds delineated by the license agreement. The core of a license is a covenant not to sue, not a transfer of title.

Unlike selling or transferring a patent to another party, licensing a patent means the licensor continues to have property rights over the patented invention. The patent owner remains the owner. A license is not an assignment of the patent. Even if the license is an exclusive license, it is not an assignment of patent rights in the patent or application. A license transfers a bundle of rights that is less than the entire ownership interest, and those rights may be limited as to time, geographical area, or field of use.

Exclusive licenses

An exclusive license prevents the patent owner (or any other party to whom the patent owner might wish to sell a license) from competing with the exclusive licensee as to the geographic region, the length of time, and/or the field of use covered by the license. Within the licensed scope, the exclusive licensee stands alone in the market. But the patent title remains with the licensor.

The line between an exclusive license and an assignment can appear thin in practice. The distinction turns on whether any ownership interest was transferred. If the licensor still holds title and has merely promised not to practice or sub-license within a defined scope, it is a license, regardless of how exclusive it feels commercially.

Nonexclusive licenses

A nonexclusive license authorizes the licensee to practice the invention alongside the patent owner and potentially alongside other licensees to whom the owner may grant identical rights. The patent owner retains the right to practice the invention itself and to license as many additional parties as it chooses.

Enforcement: who can bring an infringement action?

Because an assignee is the statutory patentee (a successor in title under § 100(d)), the assignee holds the § 281 right of action directly and can bring suit in its own name. A licensee, because it is not the patent owner, does not hold that right on the same basis. The main responsibility for monitoring, identifying, and taking action against infringers of a patent lies with the patent owner. A licensee who wishes to pursue an infringement action typically must involve the patent owner, either as a co-plaintiff or through a contractual enforcement right explicitly granted in the license agreement.

This enforcement asymmetry is one of the most practically significant differences between the two relationships. When negotiating a license, parties should address enforcement obligations explicitly: who monitors for infringement, who controls litigation, how costs are shared, and how any recovery is divided.

Partial assignments and co-ownership

A patent owner may assign a fractional share of ownership rather than the whole. Assigning a percentage interest in a patent does not create a license. It creates a co-owner. Under 35 U.S.C. § 262, 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. Co-owners may also independently grant nonexclusive licenses to third parties without consent from and without sharing royalties with the other co-owners. This default can surprise practitioners unfamiliar with U.S. co-ownership rules, particularly in cross-border joint development arrangements.

Key distinctions at a glance

Practical notes for practitioners

• Think of assignment as a sale, license as a rental. When a patent is assigned, ownership changes hands permanently (unless the assignment is subject to conditions). When a patent is licensed, the owner grants conditional or time-limited permission while retaining title.
• An exclusive license is not an assignment. The exclusivity is commercial, not legal. The exclusive licensee does not hold the § 281 right of action by virtue of exclusivity alone. Enforcement provisions must be addressed in the license agreement.
• Record assignments promptly. Section 261 makes an unrecorded assignment void against a subsequent bona fide purchaser without notice. Do not treat recording as an administrative afterthought.
• Partial assignments create co-owners, not licensees. Co-ownership under § 262 confers independent rights to practice and sub-license. The default rule can be commercially unacceptable between partners. A co-ownership agreement addressing licensing consent and revenue sharing should be in place before any fractional assignment is made.
• Employed inventors commonly pre-assign. Employment agreements routinely include an obligation to assign future inventions to the employer. Under 37 CFR § 1.46, the obligated assignee may file as the applicant even before a formal assignment is executed, based on the pre-existing assignment obligation.
• License scope determines risk. A nonexclusive licensee faces competition from other licensees and from the patent owner itself. An exclusive licensee is protected within its scope but still bears the risk that the patent owner will not aggressively enforce against infringers. Parties should align on enforcement expectations contractually rather than assuming the patent owner will act.