English contract law is a body of law regulating contracts in England and Wales. With its roots in the lex mercatoria and the activism of the judiciary during the industrial revolution, it shares a heritage with countries across the Commonwealth (such as Australia, Canada, India), and to a lesser extent the United States. It is also experiencing gradual change because of the UK's membership of the European Union and international organisations like Unidroit. Any agreement that is enforceable in court is a contract. Because a contract is a voluntary obligation, in contrast to paying compensation for a tort and restitution to reverse unjust enrichment, English law places a high value on ensuring people have truly consented to the deals that bind them in court.
Generally a contract forms when one person makes an offer, and another person accepts it by communicating their assent or performing the offer's terms. If the terms are certain, and the parties can be presumed from their behaviour to have intended that the terms are binding, generally the agreement is enforceable. Some contracts, particularly for large transactions such as a sale of land, also require the formalities of signatures and witnesses and English law goes further than other European countries by requiring all parties bring something of value, known as "consideration", to a bargain as a precondition to enforce it. Contracts can be made personally or through an agent acting on behalf of a principal, if the agent acts within what a reasonable person would think they have the authority to do. In principle, English law grants people broad freedom to agree the content of a deal. Terms in an agreement are incorporated through express promises, by reference to other terms or potentially through a course of dealing between two parties. Those terms are interpreted by the courts to seek out the true intention of the parties, from the perspective of an objective observer, in the context of their bargaining environment. Where there is a gap, courts typically imply terms to fill the spaces, but also through the 20th century both the judiciary and legislature have intervened more and more to strike out surprising and unfair terms, particularly in favour of consumers, employees or tenants with weaker bargaining power.