Set-Off Rights for Builders in Australia: Contractual vs Equitable Set-Off

What it is

Set-off is the right to reduce a claim against you by netting it off against a claim you have back the other way. If a subcontractor sues for $80,000 and you have a $30,000 cross-claim for defective work, set-off can shrink the amount you have to pay to $50,000. It is not a counter-attack; it is a defence to a debt claim, and it can be the difference between a builder surviving a payment dispute and writing a cheque under protest.

In Australia, builders deal with three flavours of set-off: contractual set-off written into the building contract, equitable set-off developed by the courts and statutory set-off in insolvency under section 553C of the Corporations Act 2001. Each has different requirements and the Security of Payment regimes in every state restrict how and when you can rely on any of them inside a payment claim dispute.

Contractual set-off

Contractual set-off lives in the words of the contract. A well-drafted head contract or subcontract will give the builder a right to deduct, withhold or set off amounts the subcontractor owes for back-charges, delay damages, defects, insurance excesses or other agreed deductions. Australian Standard contracts AS 4000 and AS 4902, plus the housing industry forms used for residential work, all carry set-off clauses that the principal or head contractor can invoke.

The scope of contractual set-off is whatever the parties have written down. That can be wider than equitable set-off because it does not need the cross-claims to be closely connected. It can also include unliquidated amounts if the clause is drafted to allow assessment by the contract administrator or superintendent. The trade-off is that the clause has to be triggered correctly: notice requirements, certification steps and timing rules in the contract have to be followed.

Equitable set-off

Equitable set-off is a common law doctrine. It allows a defendant to reduce a money claim where the cross-claim is so closely connected to the plaintiff's claim that it would be inequitable for the plaintiff to recover without accounting for it. The classic formulation is that the dealings and transactions giving rise to each claim must be closely linked.

For a builder, that usually means a cross-claim arising out of the same project, the same subcontract or the same dealings. A defects claim against a subcontractor on a job will often qualify. A claim arising from a completely separate project ordinarily will not. Equitable set-off does not depend on a contract clause, which means it is available even where the contract is silent or where the right to deduct under the clause was not triggered.

Statutory set-off in insolvency

Section 553C of the Corporations Act 2001 sets off mutual credits, mutual debts or other mutual dealings between an insolvent company and any other person. Only the net balance is provable or payable. For builders, this matters when a subcontractor or supplier hits liquidation. If you owe the insolvent party $50,000 and they owe you $35,000 on the same dealings, statutory set-off leaves $15,000. The set-off is automatic once the elements are met and it applies even without a contract clause.

Section 553C has limits. The dealings have to be mutual, meaning in the same right and between the same parties. There is also a knowledge cut-off: a party that received the credit knowing the other was insolvent cannot rely on the set-off. The High Court tightened the operation of this provision in recent decisions, and the practical effect is that set-off becomes harder to use as a defence to liquidator clawbacks.

How Security of Payment restricts set-off

The Security of Payment Acts across NSW, Victoria, Queensland, WA, SA, Tasmania, ACT and NT exist to push cash through the contracting chain. They do this by giving claimants a statutory right to progress payments backed by adjudication. To stop that pipe getting clogged with cross-claims, the Acts limit how a respondent can raise set-off.

The mechanism is the payment schedule. A respondent that wants to withhold money has to issue a payment schedule within the statutory timeframe (typically 10 business days in NSW) stating the scheduled amount and the reasons for withholding. If the respondent fails to deliver a payment schedule, it loses the right to raise reasons later, including any set-off, and the claimant can recover the claimed amount as a debt.

Even where a payment schedule is issued, the set-off has to be a genuine reason connected to the work under the contract. Some Acts contain anti-contracting-out provisions that void contract clauses purporting to exclude or restrict the Act. NSW section 34 is a clear example. So a builder cannot dodge statutory set-off rules by drafting a stronger contractual set-off and bypassing the Act.

Practical sequence for a builder

The discipline is the same on every job. Read the set-off clause in the contract and the deduction or withholding mechanism it sets up. Follow the notice steps, log the back-charges with evidence and record dates. If a payment claim arrives, get the payment schedule out inside the statutory clock with reasons that match the cross-claims. Keep contractual set-off, equitable set-off and statutory set-off all available as alternative defences in the schedule, not just the one that came to mind first.

If the counterparty goes insolvent, switch to section 553C analysis. Tally what you owe and what they owe on the same dealings before paying anything. A payment made without applying set-off becomes hard to claw back later if you become a creditor in the liquidation.