Some Members of Congress have expressed interest in the judicial award of remedies for patent infringement for more than a decade. Several bills introduced in previous sessions of Congress proposed refor ms to damages and injunctions principles in patent law. These bills were not enacted, however, and the changes made by the Leahy-Smith America Invents Act (AIA), P.L. 112-29 , were more limited. Still, concerns over the availability of remedies for patent infringement remain, as evidenced by the introduction of legislation in the 115 th Congress addressing the award of injunctions. Current law calls for the award of monetary damages against adjudicated infringers at an amount adequate to compensate for the infringement, but in no event less than a reasonable royalty. It also allows courts to increase the amount of damages up to three times that amount. Courts are also authorized to grant injunctions in "accordance with the principles of equity." In addition, attorney fees may be awarded in "exceptional cases." Persistent concerns have arisen over whether judicial remedies for patent infringement are predictable and appropriate in view of the patent owner's inventive contribution. For example, determinations of the appropriate level of damages and whether an injunction should be awarded become more complex when the patented invention forms just one feature of a complex, multi-component device, such as a cellular telephone. In addition, many commercialized products implicate hundreds or thousands of patents, in addition to those asserted in a particular litigation, and are owned by numerous unrelated enterprises. Accounting for "royalty stacking" may prove to be a difficult matter in particular cases. Other observers assert that the more routine award of attorney fees to the prevailing party would discourage what they view as abusive assertions of patent rights. This report reviews the current state of the law of patent remedies and surveys reform proposals that have come before Congress. It begins with a brief review of the basic workings of the patent system. The report then considers the award of compensatory damages for patent infringement, attorney fees, and enhanced damages. It then considers the special damages rules for design patents and reviews the law of injunctions. Individuals and firms must prepare and submit applications to the U.S. Patent and Trademark Office (USPTO) if they wish to obtain patent protection. USPTO officials, known as examiners, then assess whether the application merits the award of a patent. Under the Patent Act of 1952, a patent application must include a specification that so completely describes the invention that skilled artisans are able to practice it without undue experimentation. The Patent Act also requires that applicants draft at least one claim that particularly points out and distinctly claims the subject matter that they regard as their invention. While reviewing a submitted application, the examiner will determine whether the claimed invention fulfills certain substantive standards set by the patent statute. Two of the most important patentability criteria are novelty and nonobviousness. To be judged novel, the claimed invention must not be fully anticipated by a prior patent, publication, or other knowledge within the public domain. The sum of these earlier materials, which document state-of-the-art knowledge, is termed the "prior art." To meet the standard of nonobviousness, an invention must not have been readily within the ordinary skills of a competent artisan based upon the teachings of the prior art. If the USPTO allows the application to issue as a granted patent, the owner or owners of the patent obtain the right to exclude others from making, using, selling, offering to sell, or importing into the United States the claimed invention. The term of the patent is ordinarily set at twenty years from the date the patent application was filed. Patent title therefore provides inventors with limited periods of exclusivity in which they may practice their inventions, or license others to do so. The grant of a patent permits inventors to receive a return on the expenditure of resources leading to the discovery, often by charging a higher price than would prevail in a competitive market. A patent proprietor bears responsibility for monitoring its competitors to determine whether they are using the patented invention. Patent owners who wish to compel others to observe their intellectual property rights must usually commence litigation in the federal courts. Although issued patents enjoy a presumption of validity, accused infringers may assert that a patent is invalid or unenforceable on a number of grounds. The U.S. Court of Appeals for the Federal Circuit (Federal Circuit) possesses national jurisdiction over most patent appeals. The U.S. Supreme Court retains discretionary authority to review cases decided by the Federal Circuit. A court may subject adjudicated patent infringers to several remedies that are awarded to the victorious patent proprietor. These remedies include injunctions, monetary damages, and attorney fees. The Patent Act also allows for damages to be increased up to three times for cases of willful infringement. In contrast to copyrights and trademarks, criminal sanctions do not apply to patent infringement. The Patent Act succinctly provides for the award of damages "adequate to compensate for the infringement, but in no event less than a reasonable royalty for the use of the invention made by the infringer." In practice, patent proprietors seek to obtain their lost profits as damages when they are able to provide appropriate evidence. Otherwise a reasonable royalty serves as the default measure of damages. A patent proprietor may obtain damages based upon its lost profits if it can demonstrate that "but for" the infringement, it would have made the infringer's sales. Such an analysis must be supported by "sound economic proof of the nature of the market and likely outcomes with infringement factored out of the economic picture." For example, a patent proprietor may obtain lost profit damages if it can demonstrate that (1) the patented invention was in demand; (2) no acceptable noninfringing substitutes were available; (3) the patent proprietor possessed the manufacturing and marketing ability to exploit the demand; and (4) the amount of profit the patent proprietor would have made. If the patent proprietor cannot demonstrate entitlement to its lost profits, then it may claim damages in the form of a reasonable royalty. To determine this amount, courts typically use one of two approaches. The first, the so-called "analytical approach," provides the patent proprietor with a percentage of the infringer's profits. The second, more common approach is based upon a hypothetical negotiation. Under this technique, the reasonable royalty is set to the rate a willing patent proprietor and willing licensee would have decided upon had they negotiated the license on the date the infringement began. Courts consider many factors when determining the outcome of the hypothetical negotiation. The often cited opinion in Georgia-Pacific Corp. v. United States Plywood Corp. provides a fifteen-factor list. Actual royalty rates charged by the patent proprietor, or paid by the adjudicated infringer on comparable patents, will be considered if such evidence is available. Other factors include the advantages of the patented invention, the availability of noninfringing substitutes, the infringer's expected profits, the commercial relationship between the patent proprietor and the infringer, and industry licensing practices. For many years, reasonable royalty determinations were guided by the so-called "25% Rule." Under this principle, 25% of the infringer's profits serve as the baseline determinant for reasonable royalty damages. However, in its 2011 decision in Uniloc USA, Inc. v. Microsoft Corp ., the Federal Circuit rejected the 25% Rule. The Federal Circuit explained that the 25% Rule failed to tie a reasonable royalty base to the facts of the case at issue, even when used as a starting point. "Beginning from a fundamentally flawed premise and adjusting it based on legitimate considerations specific to the facts of the case nevertheless results in a fundamentally flawed conclusion," the Court of Appeals explained. The Patent Act limits recovery to six years prior to the filing of a complaint or counterclaim for patent infringement. For example, suppose that an inventor obtained a patent on May 1, 2007. A competitor began infringing the patent on June 1, 2008, but the inventor did not bring a suit for patent infringement until July 1, 2017. Under these facts, the period for which the inventor may recover infringement damages commences on July 1, 2011. Note that courts will ordinarily award prejudgment interest on such awards in order to compensate the patent proprietor fully for harms suffered during that six-year period, however. The availability of damages may also be limited under the so-called "marking" statute. The Patent Act encourages patent proprietors and their licensees to affix the word "patent" or the abbreviation "pat.," along with the number of the patent, on patented articles or their packaging. Alternatively, the patent holder may provide an Internet address with a posting that associates the patented article with the number of the patent. If the patent proprietor does not mark its product, then damages are available only after the infringer was specifically notified of the infringement. Filing of an action for infringement qualifies as notice under the marking statute. Ordinarily, patent proprietors may only collect damages for patent infringement that takes place during the term of a patent—that is to say, after the USPTO issues the patent and prior to its expiration date. The Patent Act provides one exception to this rule. Under current law, pending patent applications may be published "promptly after the expiration of a period of 18 months from the ... filing date." If the infringer had "actual notice" of such a published application, then the patent proprietor may obtain a reasonable royalty between the date notice was provided and the date the patent issued. Many observers have criticized patent damages awards as being uncertain and excessive, leading to social harms. For example, the Georgia Pacific factors—a list of fifteen factors to be considered within the context of a hypothetical negotiation—have been "widely criticized as ambiguous, unworkable, inherently contradictory, and circular."