As opposed to tort and unjust enrichment , contract is typically viewed as the part of the law of obligations which deals with voluntary undertakings, and accordingly gives a high priority to ensuring that only bargains to which people have given their true consent will be enforced by the courts. While it is not always clear when people have truly agreed in a subjective sense, English law takes the view that when one person objectively manifests their consent to a bargain, they will be bound.  However, not all agreements, even if they are relatively certain in subject matter, are considered enforceable. There is a rebuttable presumption that people do not wish to later have legal enforcement of agreements made socially or domestically. The general rule is that contracts require no prescribed form, such as being in writing, except where statute requires it, usually for large deals like the sale of land.  In addition and in contrast to civil law systems, English common law carried a general requirement that all parties, in order to have standing to enforce an agreement, must have brought something of value, or " consideration " to the bargain. This old rule is full of exceptions, particularly where people wished to vary their agreements, through case law and the equitable doctrine of promissory estoppel . Moreover, statutory reform in the Contracts (Rights of Third Parties) Act 1999 allows third parties to enforce the benefit of an agreement that they had not necessarily paid for so long as the original parties to a contract consented to them being able to do so.
Each contractual party must be a "competent person" having legal capacity. The parties may be natural persons ("individuals") or juristic persons (" corporations "). An agreement is formed when an "offer" is accepted. The parties must have an intention to be legally bound ; and to be valid, the agreement must have both proper "form" and a lawful object. In England (and in jurisdictions using English contract principles), the parties must also exchange " consideration " to create a "mutuality of obligation," as in Simpkins v Pays .