01. formation

The question

The contract is the principal instrument of commerce, the legal form through which the trading transaction is made binding. Before the content of a contract or the consequences of its breach can be examined, a prior question must be answered: how does a binding contract come into being at all? Out of the countless communications that pass between commercial parties, negotiations, proposals, and discussions, the law must identify the moment at which mere dealing becomes binding obligation. This sub-unit examines the constitution of a contract, the elements that together transform negotiation into a binding agreement, and asks what those elements are and how they operate in commercial dealings. The answer reveals a structure that is broadly common across the legal traditions, with one significant divergence concerning the requirement of consideration.

Agreement: offer and acceptance

The foundation of a contract is agreement, and the law analyses the formation of agreement through the connected concepts of offer and acceptance. An offer is a clear expression of a willingness to be bound on stated terms, made with the intention that it shall become binding upon acceptance by the person to whom it is addressed. An acceptance is an unqualified assent to the terms of the offer, communicated to the offeror, and upon acceptance the agreement is complete. The analysis is broadly universal across the developed legal traditions, which agree that a contract is formed when a clear proposal is met by an unqualified assent.

This structure connects to the building-blocks analysis of Course 1, for the offer and acceptance together constitute the exercise of the power, examined there, to alter legal relations by creating an obligation. The offer must be distinguished from an invitation to treat, which is not an offer but an invitation to others to make offers, as a display of goods or an advertisement ordinarily is; the distinction determines who makes the offer and who accepts it, and hence the moment and terms of the contract. An acceptance must correspond to the offer, for a purported acceptance that varies the terms is in law a counter-offer, which rejects the original offer and proposes a new one that the original offeror is then free to accept or decline.

Consider a supplier who sends a buyer a price list and the buyer who responds with an order for a quantity of goods. The price list is ordinarily an invitation to treat, an invitation to the buyer to make an offer; the buyer's order is the offer; and the contract is formed when the supplier accepts the order. Were the supplier to respond by accepting the order but adding a term, that response would be a counter-offer, and no contract would arise until the buyer in turn accepted it. The example shows offer and acceptance operating to fix the precise moment and terms at which negotiation becomes obligation.

Agreement, analysed through offer and acceptance, is therefore the foundation of the contract, and the law's careful identification of the offer, the acceptance, and the counter-offer determines when and on what terms a binding agreement comes into being.

Consideration and its civil law counterpart

Agreement alone does not, in every legal tradition, suffice to make a promise binding, and here the principal divergence between the two great traditions appears. In the common law tradition, a promise is enforceable as a contract only if it is supported by consideration, meaning that something of value in the eye of the law must be given in exchange for the promise, so that each party both gives and receives. Consideration is the common law's mark of a bargain, distinguishing the enforceable commercial exchange from the bare promise of a gift, which the common law does not enforce unless it is made in a particular solemn form.

This requirement connects to the commercial character of the law of contract, for consideration captures the reciprocal, bargained-for character of the commercial transaction, the exchange of value for value that lies at the heart of trade. The civil law tradition reaches a comparable result by a different route: it does not require consideration, and a serious agreement intended to be binding is enforceable on the basis of the parties' consent, subject in some civil law systems to a requirement of cause, a lawful reason or purpose for the obligation, which performs some of the functions consideration performs in the common law. The practical consequence of the divergence is narrower than it appears, since the ordinary commercial exchange, in which each party gives value, satisfies both the common law's requirement of consideration and the civil law's requirement of consent, and the divergence matters chiefly at the margins, as in the enforceability of a gratuitous promise.

Suppose a merchant promises to pay a sum to a supplier in return for the supplier's promise to deliver goods. In the common law, each promise is consideration for the other, the exchange of promises supplies the bargain, and the contract is binding. In the civil law, the same agreement is binding on the basis of the parties' consent to a serious exchange. Were the merchant instead to promise a pure gift, expecting nothing in return, the common law would not enforce the promise for want of consideration unless it were made in solemn form, while a civil law system might enforce a duly expressed gratuitous undertaking. The example shows the traditions converging on the ordinary commercial case and diverging on the gratuitous promise.

Consideration is therefore the common law's additional requirement for the enforceability of a promise, a requirement the civil law does not share, yet the divergence is narrow in commercial practice, since the reciprocal exchange that constitutes the ordinary trading transaction satisfies the formation requirements of both traditions.

Certainty of terms

A further requirement of formation, recognised across the traditions, is certainty of terms, the principle that an agreement is binding only if its terms are sufficiently certain for a court to ascertain what the parties have undertaken. An agreement so vague that its content cannot be determined, or one that leaves an essential matter to be settled by future agreement without supplying a means of settling it, is not a binding contract, because there is nothing the law can enforce.

This requirement connects to the function of certainty that the orientation unit identified as a central value of commercial law, for the law cannot enforce, and parties cannot rely upon, an agreement whose content is indeterminate. The requirement is applied with commercial sense, however, and the law strives to uphold the bargains of commercial parties rather than to defeat them on grounds of uncertainty. It supplies default rules to fill gaps the parties have left, implies a reasonable price or a reasonable time where the parties have not specified one, and gives effect to mechanisms the parties have provided for resolving matters left open, so that an agreement is struck down for uncertainty only where its essential content genuinely cannot be ascertained.

Imagine two enterprises agreeing on the sale of goods but leaving the price to be agreed later. If they have provided no means of fixing the price and the essential term thus remains genuinely open, the agreement may fail for uncertainty. If, however, the law of the governing system supplies a reasonable price in the absence of agreement, or the parties have provided a formula or a third-party determination, the agreement is sufficiently certain and binds. The example shows the requirement of certainty operating with commercial sense, defeating only those agreements whose content truly cannot be determined.

Certainty of terms is therefore a requirement of formation that protects the enforceability and reliability of contracts, applied by the law with a constructive disposition to uphold commercial bargains by supplying default rules and giving effect to the parties' own mechanisms wherever the essential content can be ascertained.

Intention to create legal relations

The final element of formation is the intention to create legal relations, the requirement that the parties intend their agreement to give rise to legal obligations enforceable in law, rather than to be a mere social or moral arrangement or a preliminary understanding not meant to bind. The law does not enforce every agreement; it enforces those the parties intended to be legally binding, and the intention is assessed objectively, from what the parties said and did, rather than from their unexpressed private states of mind.

This element connects formation to the normativity of law examined in Course 1, for it is the parties' intention to subject themselves to genuine legal obligation, and not merely to a social expectation, that brings the agreement within the law. In the commercial setting the requirement is readily satisfied and is presumed, since parties dealing at arm's length in the course of business are taken to intend legal consequences; the requirement does significant work chiefly in distinguishing binding agreements from preliminary or non-binding understandings, such as a letter of intent or an agreement expressly stated to be binding in honour only, by which commercial parties sometimes record a stage of negotiation without yet intending to bind themselves.

Consider two enterprises that sign a document recording the broad terms on which they hope to proceed but stating that it is subject to a formal contract to be concluded later. Although the document records an agreement of sorts, the parties have signalled that they do not yet intend to be legally bound, and the law gives effect to that intention by treating the document as a non-binding step in the negotiation rather than as a concluded contract. The example shows the requirement of intention distinguishing the binding agreement from the preliminary understanding, even where the parties have reached a measure of agreement.

The intention to create legal relations is therefore the element of formation that confines the law's enforcement to agreements the parties meant to be binding, presumed in commercial dealings yet decisive in marking the boundary between the concluded contract and the preliminary or non-binding understanding.