Every business deal in Australia, from signing up a client to buying supplies, rests on the same legal foundation: a contract. A contract is a legally binding agreement between two or more parties that a court will enforce if one side does not keep its promises. Not every agreement reaches that standard, and the difference usually comes down to five essential elements that Australian courts look for.
This guide explains what a contract is, how each of the five elements works in practice, and where agreements most often fall short. The essential elements are:
- Offer: a clear proposal to be bound on stated terms
- Acceptance: an unconditional agreement to those terms
- Consideration: something of value exchanged by each side
- Intention to create legal relations: the parties objectively intend the deal to be enforceable
- Certainty and capacity: terms definite enough to enforce, made by people legally able to contract
What is a contract?
A contract is an agreement the law recognises and will enforce. It can be a formal written document, an exchange of emails, a verbal conversation, or a combination of all three, and it can be formed in a single moment or over weeks of negotiation.
Australian contract law is mostly common law, built up through court decisions rather than a single statute. Legislation overlays some deals, such as the consumer guarantees in the Australian Consumer Law (Sch 2 of the Competition and Consumer Act 2010 (Cth)), but the five elements above remain the test for whether an agreement is enforceable in the first place.
The five essential elements
Offer
An offer is a clear statement of the terms on which one party is prepared to be bound. "I will build your website for $4,500, delivered by 30 June" is an offer. "We should work together sometime" is not, because the terms are too vague to accept.
Not every commercial statement is an offer. Price lists, shop displays, catalogues and most advertisements are invitations to treat: they invite customers to make offers, which the business can then accept or reject. The classic illustration is the advertisement in Carlill v Carbolic Smoke Ball Co [1893] 1 QB 256, where a reward promised to anyone who used a product and still caught influenza was held to be a genuine offer because it promised something definite. Australian courts take the same approach: in Rana v University of South Australia [2007] FCA 816, the Federal Court examined whether an advertisement for an event amounted to an offer or remained an invitation to treat. A quotation or proposal you send a customer is usually your offer, so it pays to state the scope, price and timing precisely.
Acceptance
Acceptance is an unconditional agreement to the offer exactly as made. It can be communicated in words, in writing, or by conduct, such as starting the work or paying the agreed amount. It must match the offer: a "yes, but I want different terms" reply is a counter-offer, not an acceptance, and it replaces the original offer rather than agreeing to it.
Acceptance does not have to be a signed document. In Empirnall Holdings Pty Ltd v Machon Paull Partners Pty Ltd (1988) 14 NSWLR 523, the New South Wales Court of Appeal held that a property developer who let a building contract proceed and took the benefit of the work could be bound even though it never signed the written contract the builder had sent. The practical lesson is the reverse of what most people assume: silence is not acceptance, but conduct that goes along with the deal can be.
Consideration
Consideration is the something of value each side gives the other. It can be money, goods, services, or a promise to do or refrain from doing something. It is what separates a contract from a gift: a promise to give someone $1,000 for nothing is not enforceable, but a promise to pay $1,000 for a day's work is.
Consideration does not have to be a fair price. A nominal amount, sometimes called peppercorn consideration, can support a contract as long as it is real and agreed. But courts look for a genuine exchange: in Beaton v McDivitt (1987) 13 NSWLR 162, the New South Wales Court of Appeal held that a promise to transfer land was not enforceable where it was conditional on an event that never happened, rather than a true exchange for the other party's acts. A promise made after the other side has already done the thing is also generally too late, because past consideration is not good consideration.
The High Court confirmed the basic rule in Ermogenous v Greek Orthodox Community of SA Inc [2002] HCA 8: unless an agreement is recorded as a deed, there must generally be real consideration. A deed is the one common exception, because a promise under seal can be enforced without consideration.
Intention to create legal relations
The parties must intend, in an objective sense, to be legally bound. The High Court explained in Ermogenous that this is not a search for what the parties secretly thought: it is an objective assessment of what their words and conduct would convey to a reasonable person, looking at the whole relationship and its circumstances. The Court also doubted the usefulness of relying on rigid presumptions about whole categories of agreement.
In practice, ordinary commercial dealings between businesses almost always carry an intention to be bound, which is why this element rarely causes problems in a well-run transaction. It matters most at the edges: arrangements between family members or friends, such as an agreement to share household tasks, are often not intended to create legal relations. Writing the words "not legally binding" on a document is relevant but not decisive, because the court looks at the whole picture rather than a single label.
Certainty and capacity
A contract must be certain enough for a court to work out what the parties promised. The terms do not have to be perfect. In Upper Hunter County District Council v Australian Chilling & Freezing Co Ltd [1968] HCA 8, the High Court held that a contract is not void for uncertainty merely because it is capable of more than one meaning: as long as it can bear a meaning, the court will give it one. The problem cases are agreements to agree later, such as "we will sort out the price in good faith", where there is nothing definite for a court to enforce.
The parties must also have the legal capacity to contract. Adults of sound mind can contract. Special rules protect minors: in New South Wales, for example, the Minors (Property and Contracts) Act 1970 (NSW) addresses the capacity of minors to enter contracts, and other states and territories have their own protections. Companies can also contract, though only through people with authority to act on their behalf, which is why a business should confirm who is signing on the other side.
A worked example: hiring a web designer
Maya runs a café in Adelaide and wants an online ordering website. She emails a designer, Rosa: "Can you build a website with online ordering for my café, for $4,500, finished by 30 April?" That is an offer: it is definite about the work, the price and the timing.
Rosa replies the next day: "Yes, I accept. I will start next week." That is acceptance, communicated in writing and matching the offer exactly. Maya pays a $1,500 deposit and Rosa does the work, so consideration moves both ways. The deal is between two businesses in a commercial context, so there is an objective intention to be legally bound. The scope, price and date are certain, and both parties have capacity. Maya and Rosa have a binding contract, enforceable even though it was negotiated entirely by email.
Now change one detail. Rosa replies: "Happy to help, let's get started and work out a fair price as we go." There is now no agreed price and no way for a court to determine one, so the price term is too uncertain to enforce as a contract. Rosa may still have other avenues of recovery for the value of her work, but she no longer has a simple, enforceable contract. That is the difference a single missing element can make.
Common misconceptions
Several common beliefs about what makes a deal binding are widespread, and each one can be an expensive surprise:
- A contract has to be in writing: not correct. Oral contracts are enforceable in Australia if all five elements are present. They are simply harder to prove, because there is no record of exactly what was agreed. Some specific contracts, such as the sale of land, have special form requirements, but they are the exception.
- A price list or shop display is an offer: usually not. It is an invitation to treat, and the customer's attempt to buy is the offer the business can accept or decline.
- Nothing is binding until it is signed: acceptance can happen by conduct, as Empirnall Holdings shows. A party who takes the benefit of the deal can be bound without a signature.
- A peppercorn fixes any deal: consideration must be real and agreed, and it is only one of the five elements. A token amount will not rescue a deal that is otherwise uncertain or never intended to bind.
- Writing "not legally binding" makes a deal safe: intention is judged objectively from everything said and done, not from a label alone, as the High Court made clear in Ermogenous.
Where a commercial lawyer helps
A commercial lawyer's job is to make sure the five elements are present and provable before you rely on a deal. In practice that means reviewing a proposal for a clear offer, confirming acceptance is recorded, checking that consideration is real, and redrafting vague terms so a court could enforce them if a dispute arose.
A lawyer also handles the parts of a deal that the elements do not cover: whether a deed is needed instead of a simple agreement, whether the person signing on the other side actually has authority to bind their company, and whether legislation such as the Australian Consumer Law adds mandatory terms to the contract. For a small business, a fixed-fee review before signing is far cheaper than enforcing or unwinding a broken deal later.
Acceptance and certainty are the usual sticking points
When a deal falls apart, the fight is rarely about all five elements at once. It usually settles on acceptance and certainty: one party says the other changed the terms, or claims "we never agreed on that", or points to a price that was never fixed. These are exactly the elements that a written record makes easy to prove and that a verbal arrangement leaves open to argument.
So before your next deal, run the five-element check. Can you point to the offer, the acceptance, the consideration and the intention to be bound, and are the key terms certain? If you can answer yes and there is a written record of it, you have a contract you can rely on. If not, that is the moment to get advice, before you commit rather than after a dispute starts.