The law of passing off prevents one trader from misrepresenting goods or services as being the goods and services of another, and also prevents a trader from holding out his or her goods or services as having some association or connection with another when this is not true.
Passing off and trademark law
A cause of action for passing off is a form of intellectual property enforcement against the unauthorised use of a mark which is considered to be similar to another party's registered or unregistered trademarks, particularly where an action for trademark infringement based on a registered trade mark is unlikely to be successful (due to the differences between the registered trademark and the unregistered mark). Passing off is a form of common law, whereas statutory law such as the United Kingdom Trade Marks Act 1994 provides for enforcement of registered trademarks through infringement proceedings.
Passing off and the law of registered trademarks deal with overlapping factual situations, but deal with them in different ways. Passing off does not confer monopoly rights to any names, marks, get-up or other indicia. It does not recognize them as property in its own right.
Instead, the law of passing off is designed to prevent misrepresentation in the course of trade to the public, for example, that there is some sort of association between the businesses of two traders.
The United Kingdom Intellectual Property Office set a leading case in their Trade Mark Opposition Decisions in 2001. It was held that two brands of confectionery both named "Refreshers", one made by Swizzels Matlow and one by Trebor Bassett, which had coexisted since the 1930s, could not be reasonably confused even by a young child intending to buy one or the other. Both still coexist.
When coming to Court, there are three elements, often referred to as the Classic Trinity, in the tort which must be fulfilled. In Reckitt & Colman Products Ltd v Borden Inc  1 All E.R. 873 Lord Oliver reduced the five guidelines laid out by Lord Diplock in Erven Warnink v. Townend & Sons Ltd. (1979 AC 731, 742 (HL)) (the "Advocaat Case") to three elements:
- Goodwill owned by a trader
- Damage to goodwill
The plaintiff has the burden of proving goodwill in its goods or services, get-up of goods, brand, mark or the thing standing for itself.
The plaintiff also has the burden of proof to show false representation (intentional or otherwise) to the public to have them believe that goods/services of the defendant are that of the Plaintiff. There must be some connection between the plaintiff's and defendant's goods, services or trade. They must show likelihood or actual deception or confusion by the public. Deception or confusion, however, does not consider a "moron in a hurry".
It is the Court's duty to decide similarity or identity of the marks, goods or services. The criteria are often: aural, visual and conceptual similarity (often applied in trade marks infringement cases).
For the element of damage to goodwill, there may be a loss or diversion of trade or dilution of goodwill. The plaintiff need not prove actual or special damage; real and tangible probability of damage is sufficient. This damage should however be reasonably foreseeable. It is not enough just to show likelihood or actual deception or confusion.
Ultimately, the Court must use common sense in determining the case, based on evidence and judicial discretion, and not witnesses.
Disclaimers may not be enough to avoid passing off or cause of action.
Extended passing off
One of the instances where passing off is actionable is the extended form of passing off, where a misrepresentation as to the particular quality of a product or service causes harm to another's goodwill. An example of this is Erven Warnink v. Townend & Sons Ltd., in which the makers of advocaat sued a manufacturer of a drink similar but not identical to advocaat, but which was successfully marketed as being advocaat.
The extended form of passing off is used by celebrities as a means of enforcing their personality rights in common law jurisdictions. Common law jurisdictions (with the exception of Jamaica) do not recognise personality rights as rights of property. Accordingly, celebrities whose images or names have been used can successfully sue if there is a representation that a product or service is being endorsed or sponsored by them or that the use of their likenesses was authorised when this is not true.
Reverse passing off
Another variety, somewhat rarer is so-called 'reverse passing off'. This occurs where a trader markets another's product or service as being his own (see John Roberts Powers School v Tessensohn  FSR 947). It is usually covered by the same court rulings as straight passing off.
- Jones, R. A. (on behalf of the Registrar and Comptroller-General) (21 February 2001). "IN THE MATTER OF APPLICATION NO. 2161647 IN THE NAME OF TREBOR BASSETT LIMITED AND IN THE MATTER OF OPPOSITION NO. 49406 THERETO BY SWIZZELS MATLOW LIMITED". ipo.gov.uk. United Kingdom Intellectual Property Office. p. 9. Retrieved 25 February 2014.
- Peter, Groves (2011). A Dictionary of Intellectual Property Law. Edward Elgar Publishing. p. 202. ISBN 978 1 84980 777 7. Retrieved 25 February 2014.
- Asprey and Garrard v. WRA (Guns) Ltd  FSR 30. However, this was expressed in the dicta of the decision in that case.
- Irvine v Talksport Ltd  FSR 35, ChD)
- Dastar Corp. v. Twentieth Century Fox Film Corp.
- Perry v Truefitt
- Satyam Infoway Ltd. v. Sifynet Solutions Pvt. Ltd.- Indian case on passing off in domain names
- Private label
- White-label product
The Law of Passing-Off by Christopher Wadlow, 3 Rev Ed edition (November 23, 2005)