In business, things change - and your contracts often need to change with them. You might want to adjust pricing, extend a delivery date, refine the scope of work, or update responsibilities as your business grows or your market shifts.
The good news: you can vary a contract after it’s signed. The key is doing it properly so the changes are clear, enforceable and don’t create new risks.
In this guide, we’ll explain what a contract variation is, when you might need one, the legal steps to make changes stick under Australian law, and the traps to avoid. By the end, you’ll know exactly how to update an agreement with confidence and protect your position.
What Is A Contract Variation?
A contract variation (sometimes called an amendment or addendum) is an agreed change to one or more terms of an existing contract. You’re not tearing up the contract and starting again - you’re modifying it.
Variations can add new terms, adjust timeframes, revise prices, change responsibilities, or remove obligations that no longer make sense. The rest of the contract continues as-is unless you expressly change it.
It’s important to separate casual conversations from legally effective changes. Not every “let’s change this” chat creates a valid variation. To be enforceable, variations need to meet the usual requirements of Australian contract law and any specific rules in your original agreement.
When Would You Vary A Contract?
There are plenty of day-to-day reasons you might update an agreement. Common scenarios include:
- Scope changes: Your client asks for additional services or extra deliverables not included in the original contract.
- Deadlines and milestones: Supply chain issues or resourcing mean a completion date needs to move.
- Pricing adjustments: Costs have increased, the project has expanded, or you’re offering a discount for a longer term.
- Compliance updates: New legislation or industry standards require you to refresh certain obligations.
- Business changes: A restructure, new co-founder or a shift in operating model calls for updated responsibilities and approvals.
Whatever the driver, it’s essential to follow a clean process so both sides are on the same page - and you avoid disputes later.
How Do You Legally Vary A Contract In Australia?
Australian law allows you to vary contracts, but there’s a right way to do it. Use this step-by-step approach to keep your changes enforceable.
1) Check The Contract’s Variation Clause
Start by reading the agreement you want to change. Many contracts include a “variation” or “amendment” clause that explains how changes must be made - for example, “in writing and signed by both parties.”
If a process is set out, follow it exactly. Courts generally uphold these requirements. Where there’s no variation clause, you can still vary the contract, but you should document the change clearly and obtain proper authority from each party.
2) Agree The Change (And Document It)
Both parties must agree to the variation. That agreement can be written, oral or implied by conduct - but some approaches are far safer than others.
- Written: The best practice is a short written amendment or addendum that both parties sign. For more significant changes, consider a deed to avoid consideration issues (more on that below). If you’ll sign electronically, make sure your execution method complies with Australian law. A quick refresher on wet-ink vs electronic signatures can help you choose the right approach.
- Oral: Verbal changes can be legally binding in some situations, but they’re hard to prove and can be undermined by a “no oral modification” clause. If you’re tempted to agree verbally, at least follow up with a confirmatory email - and know that verbal agreements carry more risk.
- By conduct: If both sides start performing as if the change is in place, a variation may be inferred. This is risky, and often leads to arguments about what was actually agreed.
Bottom line: put variations in writing, keep the wording precise, and have the right people sign.
3) Make Sure The Variation Is Legally Effective
For a variation to be enforceable, it needs to meet core legal requirements.
- Consideration or deed: In general contract law, a promise needs “consideration” (something of value) to be binding. If your variation is one-sided (for example, you agree to reduce the price without anything in return), you can execute it as a deed instead, which avoids the need for consideration. If you’re unsure when to use one, this guide to what a deed is in Australian law explains how deeds work.
- Authority to bind the party: Ensure the person signing can legally bind the company. There are two common pathways here: authority under section 126 of the Corporations Act 2001 (Cth) (an individual with express or implied authority can make, vary or discharge a contract on the company’s behalf), and execution under section 127 (formal company execution by the required officeholders). Section 127 is not the only route - it’s about how the document is executed, while section 126 is about who has authority.
- Clarity: Spell out exactly what changes. Refer to the clause number and the new wording, or attach a marked-up schedule. Avoid vague promises or “we’ll work it out later” language.
- Form requirements: If the contract requires variations to be “in writing and signed,” comply strictly. Some contracts - for example, deeds and certain property-related agreements - must be varied in writing to be effective.
4) Execute The Variation Correctly
Once you’ve agreed the changes, make sure the variation is properly signed and dated. If your original contract set out execution methods (for example, two directors, or a director and company secretary), follow those or use a valid alternative that complies with the law.
Attach the variation to the original agreement, store it with your contract records, and update any operational documents so your team works to the new terms.
5) Communicate And Implement
Variations can fall over in practice if only one side follows the new requirements. Share the change with internal stakeholders (sales, project, finance) and any external parties impacted (for example, a financier with a consent right) so everyone acts consistently with the updated deal.
What Are The Legal Limits And Common Risks?
Most contracts can be varied by agreement, but there are limits - and pitfalls to avoid.
Unilateral Variation Clauses
It’s common in SaaS, platform and standard terms to see clauses that let the supplier update terms unilaterally (for example, by posting new terms online). These clauses do appear frequently, but they’re not always enforceable as-is. In consumer and small business standard form contracts, the Australian Consumer Law’s unfair contract terms regime can make a one-sided variation right void and expose the business to penalties.
If your agreement includes (or will include) a unilateral change mechanism, consider a UCT review and redraft to minimise the risk that a court finds the clause unfair.
Writing vs. Oral Changes
There’s no general rule in Australia that consumer contracts must be in writing to be enforceable. Many everyday agreements are formed online or verbally. However, your contract may require variations to be written and signed - and certain contracts (like deeds, or agreements dealing with interests in land) generally need writing to be varied effectively. When in doubt, document changes in writing.
Franchising And Other Regulated Sectors
Some industries have special rules. For franchising, the Franchising Code of Conduct requires upfront disclosure before entering, renewing or extending a franchise agreement, and franchisors must keep their disclosure document updated (including material changes). If you’re varying a franchise agreement - especially in a way that effectively extends the term or changes fees - make sure you comply with the Code’s timing and disclosure obligations. It’s wise to get tailored advice before signing changes in these contexts.
Execution And Authority
A variation signed by someone without authority can be challenged. As noted above, authority can come from section 126 (an authorised individual) or be demonstrated by formal company execution under section 127. If you’re relying on electronic signing, ensure you follow your contract’s execution clause and the relevant execution rules.
Ambiguity And Unintended Consequences
Vague amendments or email chains can create gaps or conflicts with the original contract. Be explicit about what’s changing, and confirm that all other terms remain in force. If you’re making multiple changes over time, consider consolidating into a single, clean version of the contract.
What Documents Should You Use To Vary A Contract?
Choose a document that fits the type and significance of the change.
- Contract amendment or addendum: A short, signed document that specifies which clauses are amended, added or deleted. This is ideal for routine updates and can be prepared via a straightforward contract amendment.
- Deed of variation: A more formal document often used for significant changes or where you want to avoid consideration issues. If you need a template tailored to your situation, consider a Deed of Variation.
- Full restatement: If you’ve made multiple changes over time, or the contract is getting hard to follow, it can be cleaner to restate the entire agreement with updated terms and a new effective date.
Whichever option you choose, make sure the amendment clearly identifies the original contract (including date and parties), states the specific changes, and confirms that all other terms continue unchanged.
Practical Drafting Tips (So Your Change Sticks)
- Mirror the original structure: Refer to clause numbers and headings to make changes precise and easy to follow.
- Use schedules for complexity: If you’re updating a scope of work, service level targets or pricing, consider replacing the relevant schedule entirely rather than trying to edit in-line.
- Be explicit about timing: State the effective date for each change, and whether it applies to existing orders, renewals or only new projects.
- Check dependencies: If you update fees, do you also need to adjust payment terms, indexation, or termination rights? Ensure your variation keeps the contract balanced.
- Confirm authority and method: Decide whether to sign under section 127 execution or rely on section 126 authority, and ensure signatories match that choice.
- Keep a clean record: Store the signed variation with the original contract and your internal version control so you can produce the current terms quickly if there’s a dispute.
FAQs About Varying Contracts In Australia
Can We Just Agree By Email?
Sometimes, yes - a clear email exchange can evidence a binding variation if your contract allows it and the legal requirements are met. That said, a simple signed amendment is easier to prove, and avoids arguments about what was “really” agreed. If you do use email, include the exact wording of the change, the effective date, and get a clear “I agree” from an authorised representative.
Do We Need To Re-Do The Entire Contract?
Only if the changes are extensive or you’ve made several amendments over time. For one or two targeted updates, a short amendment or deed of variation is usually best. If the contract has become messy or confusing, a full restatement can save headaches later.
Do Both Parties Need To Sign?
In almost all cases, yes. Even where one party has a unilateral change right, you still need to implement it in the way the contract permits (for example, by giving notice, allowing a cooling-off or termination right, and updating posted terms). If your contract requires “signed” variations, make sure both parties sign the amendment.
Is An Electronic Signature Okay?
Electronic signatures are generally acceptable in Australia for most contracts and amendments, provided the signing method identifies the signer, indicates intention to be bound and is reliable for the purpose. Some documents (such as certain deeds in some jurisdictions) have additional requirements. A quick check of your execution clause and this overview of wet-ink vs electronic signatures will help you decide.
What If Our Contract Says “No Oral Modifications”?
Then stick to written, signed changes. While conduct or verbal agreements can sometimes complicate things through estoppel arguments, relying on those is risky and expensive. Use a short written amendment instead.
What If We’re Changing Only One Side’s Obligations?
If only one party is giving up something and there’s no fresh consideration flowing back, execute the variation as a deed to avoid enforceability issues. This is where using a Deed of Variation is helpful.
Key Takeaways
- A contract variation updates one or more existing terms; it doesn’t replace the whole agreement unless you restate it.
- Check the contract’s variation clause and follow it exactly - if it says “in writing and signed,” do that.
- Document changes clearly and have the right people sign, using section 126 authority or section 127 execution as appropriate.
- Use a deed where consideration is an issue, and keep the wording precise about what’s changing and when it takes effect.
- Unilateral variation clauses are common in SaaS and standard terms, but they must comply with the Australian Consumer Law’s unfair contract terms regime.
- Choose the right document for the job - a simple contract amendment for routine changes, or a Deed of Variation for more significant updates.
- Store the signed variation with your original contract and update your team so everyone follows the new terms.
If you’d like a consultation about varying a contract or sense-checking your amendment or deed, you can reach us at 1800 730 617 or team@sprintlaw.com.au for a free, no-obligations chat.
