Probuild Constructions (Aust) Pty Ltd v Shade Systems Pty Ltd; Maxcon Constructions Pty Ltd v Vadasz & Ors

The High Court of Australia considered appeals from decisions of the Victorian Court of Appeal concerning the interpretation of payment clauses in construction contracts. In *Probuild Constructions (Aust) Pty Ltd v Shade Systems Pty Ltd*, Probuild sought to recover an amount it claimed was due under a progress payment claim. Shade Systems had not paid the full amount claimed, relying on a notice of intention to claim an amount for rectification works. In *Maxcon Constructions Pty Ltd v Vadasz & Ors*, Maxcon sought to recover amounts due under progress payment claims, but the principal, Vadasz, had issued payment claims for a lesser amount, citing alleged defects.

The central legal issue before the High Court was the proper interpretation of the payment provisions in standard form construction contracts, specifically concerning the interplay between a principal's obligation to pay a progress claim and their right to set off amounts for alleged defects or incomplete work. The Court had to determine whether a principal could unilaterally reduce a progress payment by the amount of a claimed set-off, even if that set-off was disputed by the contractor, and the extent to which a principal's right to claim damages for defective work could be exercised through the mechanism of withholding payment under a progress claim.

The High Court held that the payment provisions in the standard form contracts, as commonly drafted, did not permit a principal to unilaterally determine the amount of a set-off and deduct it from a progress payment claim. Instead, the Court affirmed that a principal's right to set-off for defective work or other claims against a contractor is a right to claim damages, which must be established in accordance with the contract and general law. The Court clarified that a principal cannot simply deduct an unliquidated amount from a progress payment without proper contractual authorisation or legal determination. The Court also considered the implications of the *Building and Construction Industry Security of Payment Act 2002* (Vic) in relation to these contractual rights.

The High Court allowed the appeals, setting aside the orders of the Victorian Court of Appeal and remitting the matters for determination in accordance with the High Court's reasons.