The general rule in English law is that a promise will not be legally binding unless made in a deed, or supported by some form of consideration. If no deed is present, then for a contract to be held as legally binding both parties must provide consideration. The definition of consideration was considered and defined by Lord Dunedin in Dunlop v Selfridge Ltd [1915] AC 847, as follows: "An act or forbearance of one party, or the promise thereof, is the price for which the promise of the other is bought, and the promise thus given for value is enforceable." Often, in commercial disputes the existence of consideration is a key factor in establishing whether a valid contract exists.

A distinction is often drawn between executed consideration, and executory consideration. Executory consideration exists where the parties exchange promises. Whereas, executed consideration exists when the promisor asks for something in exchange for his promise. The promisee then provides consideration by providing to the promisor what he has requested.

There are several key legal principles that govern consideration in UK contract law. Firstly, past consideration is not valid consideration. When determining whether consideration is past, the Courts are not bound to apply a strict chronological test.

Secondly, consideration must move from the promisee. However, this does not mean it must move to the promisee. The common example of this as an everyday occurrence is when goods/services are paid for by the use of a cheque. In this scenario, the issuer of the cheque makes a promise to the supplier of the goods/services that the cheque will be honored, and the supplier provides consideration for this promise by supplying the goods/services to the customer.

Another important principle of consideration in contract law is that the consideration must be sufficient but need not be adequate. An important case precedence on this principle was set in Chappell & Co. Ltd v Nestle. Co Ltd (1960). In this case, the chocolate manufacturer Nestle held a promotional offer that members of the public would receive a free music record by sending off three wrappers of the Nestle brand to the company. The case itself involved a dispute of copyright, and the determining factor was whether a valid contract existed between the claimant and defendant, with the consideration in dispute. The Court in this case held that the wrappers formed part of the consideration, it was irrelevant that they were of trivial economic value.

Lastly, if an individual is under a public duty to perform a certain task, then the promise to carry out performance will not be valid consideration. An exception to this rule is if the individual exceeds their public duty then this may be valid consideration. The case of Glassbrook Bros v Glamorgan County Council [1925] illustrated this principle. In this case, the police provided protection during a miner’s strike, although they disputed the required amount of protection, they provided the requested amount. After the strike concluded, the police issued an invoice to provide for the increased amount of policing protection that they allocated to the strike. The invoice was refused on the grounds that the police had an existing duty. In a 3:2 decisions the Court ruled that the police had acted beyond their public duty, and so the invoice was enforceable.