Under the Construction Contracts Act 2004 (WA), an adjudicator's determination that is partially affected by jurisdictional error may be severed, with the valid portions remaining enforceable, where the invalid part did not influence the valid part and was not integral to the determination as a whole (per Buss P and Murphy JA; Martin CJ dissenting). An adjudicator determining a payment dispute has jurisdiction to consider whether a respondent's claimed set-off gives rise to a net credit balance, including by reference to amounts wrongfully withheld from earlier payment claims, provided the adjudicator does not expand the payment claim itself.
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