What makes an agreement a contract? Essential elements in Australian law

What is a contract in Australian law?

A contract is an agreement between two or more parties that the law will enforce. In plain terms, it is a set of promises that create legally binding rights and obligations: if one side does not keep its promises, the other can generally take the matter to court and have the agreement enforced.

Not every agreement is a contract. A casual arrangement with a friend, or a loose email exchange about "doing something together sometime", usually falls short. To cross the line from an understanding to an enforceable contract, an agreement needs these essential elements:

• Offer and acceptance: one party makes a clear offer and the other accepts it
• Intention to create legal relations: both parties intend the deal to have legal consequences
• Consideration: each side gives something of value
• Certainty: the essential terms are clear enough to understand and enforce
• Capacity and legality: the parties can legally contract, and the purpose is lawful

This guide works through each element, shows them operating in a realistic small-business scenario, and clears up the misconceptions that most often cause trouble.

Offer and acceptance: how agreements form

An offer is a clear statement of the terms on which one party is prepared to deal. Acceptance is an unqualified agreement to those terms. Put together, they show that the parties reached agreement on the same deal.

An offer needs to be distinguished from an invitation to treat. A price list, a shop display or an advertisement is usually not an offer at all, but an invitation for customers to make offers of their own. The classic exception is Carlill v Carbolic Smoke Ball Co [1893] 1 QB 256, where an advertisement promising a reward was held to be a genuine offer because the advertiser had shown a clear intention to be bound.

Acceptance must match the offer. A reply that changes the price, the timing or the scope of the work is generally treated as a counter-offer rather than an acceptance, and it leaves the original offer open for the offeror to accept or reject. This is why a simple "yes, agreed" is worth more than a long email negotiating terms.

Intention to create legal relations

A binding contract requires the parties to intend their arrangement to have legal consequences. That is why social promises are not contracts: an agreement to help a friend move house, or to buy a round of drinks, is not something anyone expects a court to enforce.

Intention is judged objectively, not by what the parties secretly thought. In Ermogenous v Greek Orthodox Community of SA Inc (2002) 209 CLR 95, the High Court of Australia held that the question is what a reasonable person would infer from the parties' words and conduct, and that there is no presumption against intention simply because the relationship is not a commercial one. The case concerned a church community and its archbishop, and the High Court found the engagement was capable of being a contract of employment.

For ordinary business dealings, intention is rarely the problem: courts readily infer that commercial parties meant to be bound. It becomes an issue at the border, such as work done for a relative, or a favour for a long-standing client that was never discussed in terms of money. If in doubt, the safest course is to put the arrangement in writing, because a written record is strong evidence of intention.

Consideration: the price of a promise

Consideration is what each party gives in exchange for the other's promise. It can be money, goods, services, or a promise to do something, or to refrain from doing something. The law does not enforce one-sided promises: a promise to give a friend a car for nothing is a gift, not a contract, unless it is made by deed.

Two practical rules follow. First, each party must give something; if only one side promises anything, there is no bargain. Second, past consideration is no consideration: a promise made after the other party has already done the work, such as "I will pay you a bonus for that job you finished last month", is not generally enforceable, because the work was not done in exchange for the promise. Deeds are the exception: a promise made in a deed is enforceable without consideration.

Certainty: terms must be clear enough to enforce

A court cannot enforce a vague promise. If the essential terms, such as what will be delivered, for what price and by when, are missing or left as "to be agreed later", the agreement may be an "agreement to agree" and no contract at all. This is one of the most common reasons a well-intentioned deal collapses in a dispute.

At the same time, courts are not looking for an excuse to strike deals down. In Upper Hunter County District Council v Australian Chilling & Freezing Co Ltd (1968) 118 CLR 429, the High Court emphasised that courts will be slow to hold a commercial agreement void for uncertainty, and will try to give effect to what the parties wrote wherever a meaning can be found. The practical lesson is to define the scope, the price and the timing in the deal itself, rather than assuming they will be worked out later.

Capacity and legality: who can contract, and for what

Each party needs the legal capacity to make a binding contract. Adults of sound mind can contract freely. Contracts with minors are generally voidable at the minor's option, with exceptions for necessary goods and services. A company contracts through its officers, and there are specific rules about how it signs documents: under s 127 of the Corporations Act 2001 (Cth), a company executes a document by having it signed by two directors, or by a director and the company secretary, or, for a proprietary company with a sole director, by that director.

The agreement's purpose must also be lawful. A contract to do something illegal, such as an arrangement to evade tax or to pay cash in hand to dodge obligations, is void and cannot be enforced.

The elements in action: a design job, start to finish

Maya runs a café. She emails a graphic designer, Leo: "Can you design a new logo and menu board? I will pay $2,500, with the final files to me within three weeks." Leo replies: "Yes, agreed. I will send a draft by next Friday."

Do they have a contract? Yes, and it binds both of them even though nothing has been signed:

• Offer and acceptance: Maya's email is an offer because it sets out the work, the price and the timing. Leo's reply accepting those terms is an acceptance.
• Intention: both are dealing in the course of business, so the law presumes they intended to be bound.
• Consideration: Maya gives $2,500 and Leo gives the design work.
• Certainty: the scope (logo and menu board), the price and the deadline are all defined.
• Capacity and legality: both are adults acting for lawful business purposes.

If Leo delivers three weeks late and Maya has already paid a deposit, she can enforce the deal. If Maya refuses to pay on delivery, Leo can sue for the agreed fee. The contract is enforceable because every element is present.

Contrast this with a different email: "We should do some design work together at some point, let's talk about it." There is no scope, no price, no timing and no acceptance. It is a pleasant conversation, not a contract, and neither party could enforce it.

Common misconceptions about contracts

Four misconceptions cause most of the practical trouble:

• "It is not a contract unless it is in writing and signed": This is the most expensive misconception in Australian business. Most contracts can be formed verbally or by conduct: you quote a price, the client says go ahead, you do the work, and you have a binding contract. Writing matters for proof and certainty, not for validity. There are exceptions where legislation requires writing: for example, under s 54A of the Conveyancing Act 1919 (NSW), a contract for the sale of land is not enforceable unless it is in writing and signed by the party to be charged, or by someone authorised by that party. Statutory form requirements also apply to some guarantees, credit contracts and franchise agreements.
• "A signed contract is enforceable exactly as written": Not always. Under the Australian Consumer Law (the ACL, which is Schedule 2 to the Competition and Consumer Act 2010 (Cth)), an unfair term in a standard form consumer or small business contract is void: see s 23. Since 9 November 2023, proposing, applying or relying on an unfair term in such a contract is also prohibited and can attract penalties. A contract also cannot sidestep the consumer guarantees: under s 64 of the ACL, a term that purports to exclude, restrict or modify the guarantees is void. And s 18 of the ACL prohibits misleading or deceptive conduct in trade or commerce, so a contract cannot authorise a party to mislead the other side.
• "Electronic signatures are less valid than wet ink": Generally not so. Under s 8 of the Electronic Transactions Act 1999 (Cth), a transaction is not invalid merely because it took place by electronic communication, and each state and territory has equivalent electronic transactions legislation. E-signatures are fine for most commercial documents. Some documents still need specific formalities, such as deeds, wills and certain land transactions, and companies must follow the signing rules in s 127 of the Corporations Act, which permits electronic signing.
• "We shook hands, so the deal is done": A handshake can create a binding contract if the elements are present, but it creates no record of the terms. When the other party remembers the price, the timeline and the scope differently, the handshake does not help you prove your version. That is why written terms are the safer choice for anything that matters.

When to get legal help with contracts

The elements of a contract are simple to state and surprisingly easy to get wrong in practice. For a one-off, low-value deal with a clear email trail, you may not need a lawyer at all. Professional help pays for itself in several situations:

• When you draft contracts you will reuse: such as client terms, supplier agreements or employment contracts. A lawyer can include the risk-management clauses that matter, such as limits on liability, intellectual property ownership, confidentiality, termination and dispute resolution, and can check the terms against the ACL so you do not end up with void or prohibited terms.
• When formalities matter: Deeds, company execution under s 127 of the Corporations Act, land contracts and documents that need witnesses all have rules that are easy to get wrong, and getting them wrong can make a document ineffective at the exact moment you need it.
• When you are relying on a verbal deal: A lawyer can assess whether the elements are present and help you convert the arrangement into a signed record before you invest more time or money.
• When the deal is high-value or long-term: such as a lease, a partnership or a major supply arrangement. The cost of advice is small against the cost of a dispute.

What a contract lawyer actually does in these situations: reviews the terms against the elements above, redrafts vague clauses so they are enforceable, flags compliance risks under the ACL and any industry-specific rules, and handles execution so the document is validly signed. The benefit is operational, not just legal: clear, enforceable terms mean fewer disputes, faster resolution when they occur, and less time spent reconstructing what was agreed.

The question to ask before you rely on any deal

Before you commit time, money or staff to any agreement, ask two questions. First, are all the elements present: offer, acceptance, intention, consideration, certainty, capacity and a lawful purpose? Second, if the other party disputed the deal tomorrow, could you prove what was agreed?

If the answer to either question is uncertain, the fix is usually simple: write the terms down, confirm them in an email, or get advice before you rely on the arrangement. The deals that cause real loss are rarely the ones where the elements were obviously missing. They are the ones that looked like contracts and felt like contracts, and were never tested until a dispute arose. A few minutes spent checking the elements, and proving them in writing, is the cheapest insurance your business can buy.