The six elements of a legally binding contract in Australia

A contract is an agreement the law will enforce

A legally binding agreement, or contract, is an agreement the law will enforce. If one party promises to do something and fails to follow through, the other party can take legal action, usually to recover money in damages or to force performance of the promise.

Australian contract law is largely built on the common law, the body of rules developed by courts over centuries. Whether a particular deal is binding therefore comes down to a settled set of elements rather than the form of the document. The Australian Competition and Consumer Commission describes a contract as an agreement between two or more parties that is legally enforceable, and notes that one generally exists whenever a seller makes an offer and a buyer accepts it.

For a deal to be enforceable in Australia, these elements generally need to be present:

• Offer and acceptance: one party makes a clear offer and the other agrees to it unconditionally.
• Consideration: each side gives something of value.
• Intention to create legal relations: the parties intend to be bound.
• Certainty and completeness: the essential terms are clear enough to enforce.
• Capacity: the parties are legally capable of contracting.
• Legality: the agreement does not require anything unlawful.

The sections below explain each element, then show them operating in a realistic scenario, address the misconceptions that cause the most trouble in practice, and set out when a lawyer is worth engaging.

Offer and acceptance

One party makes an offer, a clear statement of the terms on which it is prepared to deal, and the other party accepts by agreeing unconditionally to those terms. Acceptance can take several forms. The ACCC notes that a buyer can accept a contract by signing a written document, by saying they accept, or through actions such as paying for a product or clicking "I agree" on a website.

A response that changes the terms is not acceptance. It is a counter-offer, which the original party can then accept or reject, and if the original party rejects it there is no deal. Advertising, catalogues and price lists are usually treated as invitations to negotiate rather than offers capable of immediate acceptance, which is why a shop does not have to sell you the item in its window at the marked price.

Consideration

Each party must give something of value in exchange for the other party's promise: money, goods, services, or a promise to do, or refrain from doing, something. Consideration does not have to be equal in value, but it must be real and lawful. A purely one-sided promise, where one party gives nothing in return, is generally not enforceable as an ordinary contract. This is one reason the law developed the deed, a more formal instrument that can be binding without consideration, which makes deeds useful where one party is promising something for no exchange.

Intention to create legal relations

The parties must intend their agreement to be legally enforceable. In Ermogenous v Greek Orthodox Community of SA Inc [2002] HCA 8, the High Court held that intention is assessed objectively, from all the circumstances of the case, rather than by applying a rigid presumption. In practice this element is readily satisfied in commercial dealings between businesses. If a supplier and a customer negotiate a deal in a business context, it will be difficult for either party to later argue there was no intention to be bound, which is why a handshake deal over a quote can be enforceable.

Certainty and completeness

The essential terms must be clear enough for a court to enforce. The classic statement of the test comes from Upper Hunter County District Council v Australian Chilling and Freezing Co Ltd (1968) 118 CLR 429: an agreement is enforceable if it is capable of a meaning, and courts are slow to hold a commercial agreement void for uncertainty. But if a core term such as price, scope or duration is missing, with no mechanism for working it out, the deal may not be enforceable at all. An arrangement to settle the details later is generally not a binding contract, because the parties have not actually agreed on what they will do.

Capacity

The parties must have the legal capacity to contract. Adults of sound mind can contract. Special rules apply to minors: in NSW, s 19 of the Minors (Property and Contracts) Act 1970 (NSW) provides that a minor's participation in a civil act is presumptively binding only if it is for the minor's benefit at the time.

Companies are separate legal persons that act through people, so the person signing must have authority to bind the company. Section 127 of the Corporations Act 2001 (Cth) sets out reliable methods of company execution, such as signature by two directors, or by a director and a company secretary, and lets other parties rely on the assumptions in s 129 that the document was validly executed. Signing without authority is a common reason a deal later falls apart.

Legality

An agreement to do something illegal will not be enforced. If performing the contract would involve breaking the law, the illegal terms, and sometimes the whole contract, are void or unenforceable, and a court will generally leave the parties where it finds them.

Worked example: the fit-out quote accepted by email

A café owner in Melbourne asks a commercial joiner to quote for the design and construction of a new fit-out. The joiner emails a quote: $85,000 for design and build, completed by 30 June, with a list of what is included. The café owner replies "Yes, go ahead."

All six elements are present. The quote is the offer and the reply is the acceptance. The joiner's services and the $85,000 are the consideration. The commercial context shows intention to be bound. The scope, price and completion date give certainty. Both parties are capable of contracting and the work is lawful. If the joiner delivers late or the café owner refuses to pay, the email exchange itself can be enforced in court, even though no formal contract was ever signed.

Now change one detail. Suppose the joiner's email had said "we will agree the final price once the design phase is complete." The price, an essential term, is left open with no agreed way of fixing it. If the parties fall out before the design phase finishes, a court may find there is no binding contract yet, only an arrangement to negotiate. The difference between the two versions is a single sentence, but it decides whether the café owner has a claim.

Misconceptions that cost businesses money

Five beliefs about how contracts come into existence cause most of the expensive surprises in practice:

• Writing and signing: a contract does not need to be in writing and signed to be binding. The ACCC confirms acceptance can occur by words or conduct, such as paying for goods or clicking "I agree". Verbal agreements are enforceable; the difficulty is proving their terms, not the principle.
• Signed documents: a signed document is not automatically a binding contract. Execution can fail for reasons unrelated to the words, such as the signer lacking authority, the document being expressed "subject to contract", or an essential element being missing. Conversely, an unsigned exchange of emails can bind the parties.
• Email informality: an email chain that shows an offer, an acceptance and an intention to be bound can form a contract. Electronic transactions laws, such as s 9 of the Electronic Transactions Act 2000 (NSW), treat an electronic signature as meeting a signature requirement where a method identifies the signer and indicates their intention, is reliable enough for the purpose, and the signer consents.
• Agreeing the details later: courts will not enforce an arrangement where essential terms are left open with no mechanism for deciding them. If you need to move quickly, lock in the core terms in a short written document and provide a process for finalising the rest.
• One-sided terms: an unfair term is not enforceable merely because the other party agreed to it. Unfair contract terms in standard form contracts with consumers and small businesses are void under the Australian Consumer Law, and since 9 November 2023, proposing, using or relying on an unfair term in a standard form contract is banned and can attract penalties, as the ACCC explains.

When a lawyer is worth engaging

Many routine deals do not need a lawyer, but a practitioner adds real value at specific points:

• Choosing between an agreement and a deed: Deeds do not require consideration and carry a longer limitation period. In NSW, an action on a deed can be brought within 12 years, compared with six years for ordinary contracts, under ss 14 and 16 of the Limitations Act 1969 (NSW). Deeds also have stricter formalities: s 38 of the Conveyancing Act 1919 (NSW) requires a deed to be signed and sealed and attested by at least one witness who is not a party, although electronic deeds are now permitted in NSW under s 38A.
• Checking execution: A lawyer can confirm who has authority to sign for a company, whether to use the s 127 execution block under the Corporations Act 2001 (Cth), and whether electronic signing is available, which it is for most business documents.
• Reviewing standard terms: Because unfair terms can now attract penalties, a periodic review of standard form contracts for one-sided variation rights, broad unilateral termination rights or excessive liability limits is a sensible precaution.
• Sorting out disputes: Where terms are uncertain, a variation is disputed, or a breach has occurred, early advice on whether a binding contract exists and what it requires is far cheaper than litigating that question later.

The deal you can't prove

The misstep that causes the most loss in practice is not signing the wrong document. It is relying on a deal whose essential terms were never pinned down, so that when the relationship sours there is no enforceable contract and no reliable record of what was agreed. Before you rely on any deal, ask yourself whether you could reconstruct all six elements from your records if the other side walked away tomorrow. If you could not, formalise the deal now, while goodwill still exists.