Offer And Acceptance: How Australian Contract Law Works

Every day, you make deals in business - from hiring a new team member to confirming a supply price or locking in a major client. The tricky part is knowing when those talks cross the line into a legally binding contract.

That “line” is offer and acceptance. Get this right and you’ll know when a deal is final, when negotiations are still open, and how to avoid disputes about “what we agreed”.

In this guide, we break down how offer and acceptance work under Australian contract law in plain English. We’ll explain what counts as an offer, the different ways acceptance can happen (including online), how counter offers affect negotiations, and when a contract actually becomes binding. We’ll also flag important caveats (like where a contract must be in writing or when an offer can’t be withdrawn).

What Do “Offer” And “Acceptance” Mean In Australian Contract Law?

Every contract in Australia begins with an offer followed by acceptance. These are the building blocks of a binding agreement, alongside intention to create legal relations, consideration (something of value), certainty of terms, capacity and legality.

• Offer: A clear promise to be bound on specific terms if the other party agrees.
• Acceptance: An unqualified agreement to all terms of that offer.

If those elements are present - together with intention, consideration and sufficiently certain terms - you have a binding agreement. It can be in writing, verbal, a series of emails, or formed by conduct. Verbal agreements can be enforceable in many cases, though proving the exact terms is harder than with a written record.

As you weigh up whether a contract exists, it also helps to understand what isn’t an offer. Many things we see in business are invitations to others to make an offer, not offers themselves.

For example, most advertisements, price lists and website displays are typically an invitation to treat (an invitation for the customer to make an offer), not a binding promise to sell at that price. The same goes for many quotes unless they’re framed as firm commitments. To unpack this distinction, see the difference between an invitation to treat vs offer and whether a quotation is legally binding.

What Counts As A Valid Offer?

An offer must be clear and definite. It should show a present intention to be legally bound if the other party accepts.

• Typical offers: “We’ll supply 1,000 units at $9.50 plus GST, delivery in 14 days - please confirm by email.”
• Not usually offers: “We’d love to work together,” “We’re exploring supply options” or “Indicative pricing subject to change”.

Key principles to keep in mind:

• Clarity matters: The essential terms (e.g. goods/services, price, timing) should be identifiable. If critical terms are vague, the offer may be too uncertain to accept.
• How long does an offer stay open? Unless stated, an offer can lapse after a reasonable time, on rejection, on counter offer, or on revocation (withdrawal) before acceptance.
• Can you make an “irrevocable” offer? If the other party gives value to keep an offer open (an “option contract”), you can be bound not to withdraw it during the option period. Otherwise, in general, you can revoke an offer any time before it’s accepted.

It’s also possible to make offers to the world at large (e.g. “return of lost property for a $500 reward”). These are usually accepted by performance rather than a promise - known as unilateral contracts.

How Does Acceptance Work (Email, Online And In Person)?

Acceptance is the “yes” that finalises a deal - but it must be clear, communicated in the required way, and mirror the offer’s terms.

1) Acceptance Must Match The Offer

If you agree to all terms without adding new ones or changing anything, that’s acceptance. If you vary a term (even a minor one), you haven’t accepted - you’ve made a counter offer (see below).

2) Follow Any Prescribed Method Of Acceptance

The offeror can prescribe a method of acceptance (e.g. “reply by email only” or “sign and return by 5pm Friday”). If the method is mandatory and you accept in a different way, the offeror can generally insist that you accept as prescribed. If the method looks more like a suggestion, a reasonable alternative may still work.

3) Communication (Including Postal And Electronic Rules)

• General rule: Acceptance must be communicated to the offeror to be effective (silence will not usually amount to acceptance).
• Postal rule: In limited cases involving post, acceptance may be effective on posting (not receipt), unless the offer excludes it or other circumstances make it inapplicable. Many modern offers exclude the postal rule by requiring receipt or electronic acceptance.
• Electronic acceptance: Acceptance can occur by email, clickwrap (“I agree” tick box), e-signature or similar, provided the acceptance is clear and the terms are reasonably available to the accepting party. A clear set of website terms and conditions and a transparent checkout flow are crucial here.

If you’re confirming a deal via email, you can still create a binding contract. The key is that your email chain shows a clear offer, clear acceptance and certainty about the terms. For more on this, see when an email can be legally binding.

4) Acceptance By Conduct

Sometimes actions speak louder than words. If a party starts performing under the offer (for example, supplying goods after a clear purchase order), their conduct can amount to acceptance. This is common in routine trade dealings - but it can create confusion if standard terms conflict. In those cases, making your terms of sale prominent and requiring explicit acceptance reduces risk.

5) Silence Is Not Acceptance (With Narrow Exceptions)

Silence does not normally equal acceptance. A narrow exception may arise where there’s a consistent past course of dealing that makes silence a reasonable way to accept, but this is uncommon and fact-specific.

6) Who Can Accept?

Only the person or entity to whom the offer is made can accept it (or someone properly authorised to accept on their behalf). If a company is accepting a written agreement, consider using proper execution methods such as signing under section 127 of the Corporations Act to improve certainty.

Counter Offers, Negotiations And “Battle Of The Forms”

A counter offer is a response to an offer that changes a term or adds a new condition (e.g. “we accept, but delivery must be Friday”). Legally, it rejects the original offer and puts a new offer on the table.

• No contract until clear acceptance: If both sides keep changing terms, there’s no contract until one side unconditionally accepts the other’s last offer.
• Standard terms clash: Where each business tries to contract on its own standard terms (purchase order vs invoice terms), disputes can arise over whose terms “won”. The safest path is to call out which terms apply - and ensure the other party expressly accepts them before work starts.
• Amending drafts: Redlining a draft document is negotiating, not accepting. A deal is only done when both parties agree on the final terms and accept them (often by signing). If terms change later, use a proper variation - here’s a practical overview of amending contracts in Australia.

When Does A Contract Become Binding - And What Are The Caveats?

A contract becomes binding when there’s a valid offer, unconditional acceptance, intention to be legally bound, consideration, certainty of terms, and capacity/legality. But there are important caveats to avoid surprises.

1) Some Deals Must Be In Writing

While many contracts can be formed orally or by email, certain types typically need writing to be enforced - for example, contracts for the sale or disposition of interests in land and many guarantees (these requirements can vary by state legislation). Even where writing isn’t strictly required, a written record is strongly recommended so you can prove the terms later. If you’re unsure, get advice before relying on a handshake or informal email chain.

2) You Can’t Withdraw An Offer After Acceptance

Revocation is only effective before acceptance and must be communicated (directly or via a reliable third party). Once the other party has validly accepted, a binding contract exists and the offeror cannot revoke. If you need flexibility, build it into the offer (e.g. a right to withdraw before acceptance, expiry times, or conditions precedent).

3) Option Contracts And Deeds

Consideration is normally required for a simple contract. However, some commitments are made as deeds, which do not require consideration if properly executed. Option contracts (where a party pays to keep an offer open for a period) can make offers irrevocable during the option window. If you need a firm commitment without consideration, a properly executed deed may be appropriate.

4) Clear Terms Reduce The Risk Of Invalidity

If the essential terms are vague, missing, or too uncertain, a court might find no contract was formed. Price, scope, timing and risk allocation should be clear. This is a common issue in “agreements to agree” or where key commercial points are left open. If you’re concerned about enforceability, check the common reasons a contract can be invalid.

5) Intention And “Subject To Contract” Language

Parties must intend to create legal relations. If both sides say the deal is “subject to contract” or “subject to board approval,” that is usually a signal that no binding contract is formed until the condition is satisfied or a formal document is signed.

6) Evidence And Proof

A contract might exist but be hard to prove. Keep a clean paper trail: the final offer, the acceptance, and the agreed terms. If you need to rely on your standard terms, surface them prominently and capture explicit acceptance (ticks, signatures, or written confirmations).

Practical Tips And Documents To Lock In Offer And Acceptance

Putting the right documents and processes in place will help you form contracts cleanly and prove them later if anything goes wrong.

• Service Agreement or Supply Agreement: A written agreement that sets out scope, pricing, payment terms, service levels, IP and liability - and includes signature blocks for acceptance. If you sell services, a tailored Service Agreement sets expectations and reduces disputes.
• Terms Of Sale: For recurring transactions, publish clear Terms of Sale and require customers to accept them with each order (online or offline).
• Website Terms & Conditions: If you sell or sign customers up online, ensure your Website Terms and Conditions are visible and accepted via a clear clickwrap flow.
• Privacy Policy: If you collect personal information, you’ll likely need a compliant Privacy Policy explaining what you collect and how you use it.
• Employment Contract: When hiring, issue a formal Employment Contract. A job offer is the offer; signing is the acceptance.
• Execution And Authority: When contracting with companies, ensure documents are properly executed (for example, by section 127 methods) and that the person signing has authority.
• Variations: If terms change later, document them via a short, clear variation rather than relying on emails scattered across threads. This prevents uncertainty about what was accepted.

Finally, remember that a contract can be created without a signature (for example, by email or conduct). If you prefer not to be bound until a document is signed, say so explicitly in your communications - and add a “subject to contract” qualifier while negotiating.

Everyday Scenarios (And How To Keep Them Clean)

• Customer orders: A customer submits an online order. That’s usually their offer to buy. Your order confirmation is acceptance that forms the contract. Make sure your terms are accessible before checkout and that acceptance is captured via an “I agree” tick box.
• Email negotiations: If you write “we agree” to the other side’s final terms, you may have accepted - even if the formal contract isn’t signed yet. If you only intend to be bound when the document is executed, say so in the email and keep discussions “subject to contract”.
• Quotes: A quote is often an invitation to treat, not an offer. If you want a quote to be binding on acceptance, make the language clear and include an expiry date.
• Verbal deals: Many verbal agreements are enforceable, but evidence can be an issue. Where possible, follow up with a short written confirmation. This is especially important where you’re relying on verbal agreements for key commercial terms.

Quick FAQ

Can I withdraw an offer after the other side accepts?
No. Revocation only works before acceptance and must be communicated. After acceptance, you’re bound (subject to any agreed termination rights).

Does silence count as acceptance?
Generally, no. Acceptance must be a clear, positive act. Rare exceptions may arise from consistent past dealings.

Is an email agreement binding?
It can be, if there’s a clear offer, unqualified acceptance and certainty of terms. If you only want to be bound on signature, say so and use execution formalities.

What if we start work before signing?
Conduct can amount to acceptance. To avoid uncertainty, put in place the core documents first, such as a Service Agreement and Terms of Sale, then start work.

Key Takeaways

• Offer and acceptance are the core ingredients of a binding contract, alongside intention, consideration and certainty.
• An offer must be clear and definite; acceptance must mirror the offer’s terms without changes. Any change is a counter offer.
• Acceptance can occur in writing, by conduct, by email, or online (e.g. clickwrap), and you should follow any prescribed method set out in the offer.
• Some agreements should be in writing to be enforceable; once an offer is accepted, it can’t be revoked, and option contracts can make offers irrevocable for a period.
• Reduce risk with strong documentation - a tailored Service Agreement, clear Website Terms and Conditions, Terms of Sale, a Privacy Policy and proper execution processes.
• If in doubt about whether a contract has formed or how to capture acceptance cleanly, get advice early to prevent costly disputes.

If you’d like a consultation on ensuring your offer and acceptance process is legally sound for your business, you can reach us at 1800 730 617 or team@sprintlaw.com.au for a free, no-obligations chat.