The first requirement in English contract law for the formation of a binding contract is an agreement between the parties. An agreement is reached when an offer made by the offeror receives unqualified acceptance from the person to whom it is addressed (the offeree).

An offer is an expression of the offeror’s willingness to be bound on certain ascertainable terms with an intention that those terms will become binding as soon as they are accepted by the offeree.

An offer must be distinguished from an invitation to treat.