Last Updated on 13/03/2026 by Damin Murdock
The case of Leighton v Arogen [2012] NSWSC 1323 remains a critical reminder that the NSW Security of Payment Act is a structured process designed for speed and fairness. If a party disrupts that structure by changing the basis of their claim at the last minute, the entire adjudication determination may be quashed.
The NSW “Lock-In” Rule: Section 20(2B)
Under Section 20(2B) of the NSW Act, a respondent cannot include reasons for withholding payment in their Adjudication Response unless those reasons were already raised in the Payment Schedule.
The Nuance for 2026: While this “locks in” the respondent, NSW courts (including Lipman Pty Ltd v A-Civil Aust Pty Ltd [2025]) have clarified that:
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Amplification is allowed: A respondent can provide more detail or evidence to support a reason already listed in the schedule. They aren’t limited to a “word-for-word” mirror of the initial schedule.
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Exclusion, not Invalidation: If new reasons are raised, the adjudicator must generally disregard them, but this does not automatically make the entire response invalid.
Leighton v Arogen: When “Moving the Goalposts” Breaks the System
The real danger in Leighton v Arogen arose when the Claimant materially changed the basis of their claim within the Adjudication Application.
The Natural Justice Problem: Because the Respondent (Leighton) was constrained by the “lock-in” of Section 20(2B), they found themselves unable to answer a claim that looked significantly different from the one they first received. McDougall J quashed the determination because the adjudicator:
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Permitted the Claimant to advance a claim in a way the Respondent could not fairly answer.
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Failed to properly consider the Respondent’s attempts to address these changed claims.
This created a material denial of natural justice. The adjudication process is meant to resolve the dispute identified in the Payment Claim and Schedule—not a new dispute manufactured in the Adjudication Application.
Ensuring Your Determination Sticks
With Victoria’s 2025 reforms now influencing industry standards, specifically regarding unfair time bars and expanded powers to void certain contract conditions, NSW practitioners must remain focused on the strict procedural requirements of the 1999 Act.
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Consistency is Key: Ensure your Adjudication Application is an expansion of your Payment Claim, not a replacement for it. If you shift the “nexus” of your claim (e.g., moving from a simple variation claim to a complex delay-based argument), you risk a jurisdictional challenge.
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Respondent Vigilance: If you see a Claimant “moving the goalposts” in their application, highlight the natural justice risk immediately to the adjudicator.
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ANA Code of Practice: Be aware that while the Minister may prescribe a Code of Practice for Authorised Nominating Authorities (ANAs) in NSW, your primary protection against “selective disclosure” or procedural unfairness remains the Supreme Court’s power to review for jurisdictional error.
At Leo Lawyers, we help contractors and principals navigate the high-speed adjudication process with applied legal judgment. We ensure your Payment Schedules are robust enough to allow for future “amplification” while keeping your opponents strictly to the claims they first made.
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DISCLAIMER: This is not legal advice and is general information only. You should not rely upon the information contained in this article, and if you require specific legal advice, please contact us.
Damin Murdock (J.D | LL.M | BACS - Finance) is a seasoned commercial lawyer with over 17 years of experience, recognised as a trusted legal advisor and courtroom advocate who has built a formidable reputation for delivering strategic legal solutions across corporate, commercial, construction, and technology law. He has held senior leadership positions, including director of a national Australian law firm, principal lawyer of MurdockCheng Legal Practice, and Chief Legal Officer of Lawpath, Australia's largest legal technology platform. Throughout his career, Damin has personally advised more than 2,000 startups and SMEs, earning over 300 five-star reviews from satisfied clients who value his clear communication, commercial pragmatism, and in-depth legal knowledge. As an established legal thought leader, he has hosted over 100 webinars and legal videos that have attracted tens of thousands of views, reinforcing his trusted authority in both legal and business communities."
