In the recent case of Cooper & Oxley Group Pty Ltd v Koitka[1]the Supreme Court of Western Australia delivered its first decision regarding a judicial review (JR) application in respect of an adjudicator’s determination made pursuant to the Building and Construction Industry (Security of Payment) Act 2021 (WA) (SOPA).
The case serves to remind parties to clearly set out their claims and position in payment claims and schedules, and confirms that the Court has no intention of departing from the well-established and widely applied principles governing judicial review of adjudication determinations made under security of payment legislation.
The head contractor (Cooper & Oxley) engaged a subcontractor (Caledonia) to carry out works at a golf course. Disputes arose between the parties concerning Caledonia's work, and the sufficiency of the supporting material that Caledonia provided for the nine progress claims Caledonia submitted.
Caledonia suspended its work, following which Cooper & Oxley terminated the subcontract, relying on a termination for convenience clause. After the subcontract was terminated, Caledonia submitted progress claim 10, claiming $223,726.84.[2] The progress claim was not submitted as a ‘final’ claim.[3] In a letter to Caledonia, Cooper & Oxley disputed the validity of the progress claim but, as a precautionary measure, also gave a payment schedule, which included a payment certificate and a spreadsheet assessing the progress claim.[4]
Relying on the termination, Cooper & Oxley assessed the progress claim as if it were a ‘final’ claim. It did so in an unusual way; by assessing Caledonia’s works as 100% complete, valuing the completed works, and then applying a credit for the value of the original scope of work which remained to be completed.[5] It then applied further deductions and set offs for alleged defects and outstanding debts, all of which resulted in the claim being valued at negative $543.85.[6] Relevantly;
The adjudicator found that the progress claim was valid, and that it was not a final claim.[10] He held that because it was not a final claim, the way in which Cooper & Oxley had assessed the claim (certifying the work as complete then applying deductions for unfinished scope work) was improper.[11] His determination included a table summarising the parties’ respective positions, which did not refer to amounts Cooper & Oxley said it had paid, or to any backcharges[12] and he held that Cooper & Oxley should pay Caledonia $131,935.76.[13]
Cooper & Oxley applied for judicial review of the decision on the basis that it considered the adjudicator had failed to perform his function under s38(1)(a) of the SOPA (which requires an adjudicator to determine the amount of the progress payment, if any, to be paid by the respondent to the claimant) because the adjudicator:
The Court found that the adjudicator had accepted that he needed to take into account Cooper & Oxley’s set offs, and amounts it contended had already been paid, to the extent these matters had been raised by Cooper & Oxley.[14] The Court identified four examples of the adjudicator having expressly referred to set off rights[15] and stated that there was no jurisdictional error simply because the adjudicator did not refer specifically to cl 17.10 (right to set off) or cl 36.8 (termination for convenience) of the subcontract.[16]
Cooper & Oxley argued that a statement made by the adjudicator, that “[Cooper & Oxley] does not have the right to make deductions for unfinished scope work in relation to this claim” was evidence that the adjudicator’s decision was wrong, because clause 17.10 entitled Cooper and Oxley to apply set offs for ‘potential’ claims. The court rejected this, noting the statement had been made in the context of the adjudicator’s decision that progress claim 10 was not a ‘final claim’, meaning Cooper & Oxley’s method of assessing it as if it was a final claim was wrong, and in any event:
There was no failure by the adjudicator to perform his functions in respect of the matters raised by Ground 1 because he accepted that he was required to take into account, and he actually did take into account, the previous payments and set offs to the extent they were asserted by Cooper & Oxley, regardless of whether the contract was terminated.[18]
Cooper & Oxley argued that the adjudicator failed to have any, or any proper, regard to specific set offs raised in the payment schedule and adjudication response submissions in respect of:
The court held that there had been no jurisdictional error in relation to Cooper & Oxley’s set offs for defect rectification; relying on Martinus Rail Pty Ltd v Qube RE Services (No 2) Pty Ltd,[19] Lemonis J stated that any misunderstanding as to the relationship between the reasons for set offs given by Cooper & Oxley in the payment schedule and the detail contained in its adjudication response would not amount to a jurisdictional error and it was evident from the references to submissions and supporting documents included in the adjudicator’s reasons that he had considered and interrogated the documents provided,[20] so the court was not willing to infer that the regard given to those documents was insufficient simply because the adjudicator had rejected the claims.
However, the Court found that there had been jurisdictional errors made in respect of Cooper & Oxley’s attempts to set off backcharges and debts due.
Lemonis J held that it was not immediately clear on the face of the spreadsheet included in the payment schedule that Cooper & Oxley intended to set off the backcharges identified[21] but, having reviewed Cooper & Oxley’s adjudication response submissions and supporting statutory declaration himself, he was satisfied that the spreadsheet did identify that Cooper & Oxley intended to set off the backcharges, and that Cooper & Oxley had maintained that claim during the adjudication proceedings.[22] Despite stating (twice) that it was “understandable” that the adjudicator had not appreciated Cooper & Oxley’s claim for a set off in respect of the back charges,[23] Lemonis J held that the absence of the backcharges in the adjudicator’s summary table and the absence of any specific findings relating to the backcharges conveyed that the adjudicator had failed to consider a material matter raised by Cooper & Oxley,[24] and that this failure amounted to a jurisdictional error.[25]
In the determination, the adjudicator had stated that he could find no reason in the payment schedule to support Cooper & Oxley’s attempt to set off a debt due to it from Caledonia. Lemonis J found that this was “not explicable” in circumstances where the set off claim was included in the payment schedule spreadsheet under the heading “OUTSTANDING DEBTS DUE - PROGRESS CLAIMS” and clearly referenced that an outstanding debt from progress claim 9 as the basis for the set off.[26] Lemonis J noted that, had the adjudicator’s reasons indicated he had considered the documents comprising progress claim 9 and could find no evidence to support the set off of the debt, it may have given rise to an error of fact, rather than law.[27] However, where payment schedule 9 was before the adjudicator, and the determination merely stated that the adjudicator was not able to find any reason in the payment schedule for the deduction, Lemonis J was willing to draw an inference that the adjudicator had not had regard to whether progress claim 9 supported the claimed set-off,[28] and that the failure to address a material aspect of Cooper & Oxley’s response to the progress claim amounted to a jurisdictional error.
As the first reported decision on a JR application pursuant to the SOPA, Cooper & Oxley v Koitka is important. The decision sets out and approves a number of principles which have previously been widely applied in both Western Australia, in respect of the Construction Contracts (Former Provisions) Act 2004, and in the east, in respect of the various states’ SOPA equivalent legislation, namely;
In the context of the well-developed body of case law surrounding judicial review of administrative and quasi-judicial decision making, none of the statements of law referenced in the decision are surprising or unusual.
However, there is one aspect of the decision which is unusual; the court’s finding that the adjudicator made jurisdictional errors in respect of the backcharges claim was based on the court’s interpretation of Cooper & Oxley’s payment schedule. This is misaligned with earlier decisions by courts in New South Wales, which support the ‘well settled’ view that “it is a matter for an adjudicator and not the Court on judicial review to construe the Payment Schedule”.[36]
Relevantly, when considering the issue of the backcharges, Lemonis J acknowledged that it was not clear on the face of the payment schedule that Cooper & Oxley was claiming a set-off in respect of backcharges and that it was “understandable that the adjudicator did not appreciate” this.[37] He went on to state that his task was “to determine whether Cooper & Oxley, by its payment schedule, made a claim to set off the backcharges. If it did, then there will be jurisdictional error, as the adjudicator would have failed to consider a material matter raised by Cooper & Oxley in response to the progress claim.”[38] However, authority out of New South Wales provides that the power to determine how payment claims and schedules are construed is vested only in the adjudicator,[39] and it is not part of a court’s function to re-examine those documents in order to determine whether the adjudicator’s approach was erroneous.[40]
Lemonis J went on to find that the claim for backcharges had been raised in the payment schedule and maintained in Cooper and Oxley’s adjudication response submissions. Despite an earlier acknowledgment that the absence of a reference to a particular matter or thing does not necessarily support an inference that a jurisdictional error has occurred,[41] Lemonis J considered that the lack of references to the backcharges in the determination (and in particular, their omission from a table summarising the parties’ positions) indicated that the adjudicator had failed to consider matters raised in the payment schedule and held that this failure amounted to a reviewable error.[42]
Whilst the lack of references to the backcharges may have been evidence of the adjudicator’s failure to consider that matter, the widely accepted position in New South Wales is that there are a range of possible explanations for an adjudicator’s failure to reference a particular matter or thing, only one of which is that the material was not considered.[43] In the seminal decision of Ceerose Pty Ltd v A-Civil Aust Pty Ltd,[44]the Appeal Court of the Supreme Court of New South Wales[45] noted that written reasons are not comprehensive statements of all aspects of a decision-maker’s thinking and are not required to deal with all the evidence or submissions that inform a decision; as a result, their scope and level of detail will “inevitably reflect the practical circumstances under which [a decision-maker] is operating”.[46] In the case of adjudications, these practical circumstances include an obligation to determine an adjudication application within an extremely limited time frame, notwithstanding the enormous volumes of material submitted by the parties to the adjudication, so “[i]t is inevitable that… an adjudicator will spend more time on some items within a claim than on others”, and their written determination may or may not reflect their reasons for doing so.[47]
The Court of Appeal in Ceerose noted that other inferences which might be drawn from an adjudicator’s lack of reference to a particular issue or submission include that one party’s submissions were lacking in substance, and that a submission, or relevant facts or law may have been misunderstood[48] – as was apparently the case in Cooper and Oxley. However, as the Court of Appeal in Ceerose pointed out, a misunderstanding might explain a lack of references in the reasons without evidencing a lack of consideration and, whilst adjudicators are required to consider the matters raised by the parties, they are not under any positive duty to deal with those matters correctly.[49]
How the case law in Western Australia regarding judicial review of determinations made under the Building and Construction Industry (Security of Payment) Act 2021 (WA) develops remains to be seen.
One thing is certain though - Cooper & Oxley v Koitka stands as a firm reminder to parties of the need for clarity in payment claims, schedules, and adjudication submissions. Lemonis J’s final observation demonstrates that this is a matter the Court is keen for construction industry participants and their legal representatives to address:
“The [SOPA] envisages that the procedures relating to progress claims are carried out expeditiously, efficiently and fairly, recognising that a progress claim is an interim claim. To achieve these objectives, the parties to a progress claim need to make sure their position in respect of the claim is clearly expressed. Doing so significantly reduces the need for, and scope of, proceedings such as these, and the legal costs associated with them. It is also important to bear in mind that clarity is usually achieved by the use of plain language.”
This article was written by Briony Whyte, Senior Associate Construction.
[1] [2026] WASC 4, (Cooper & Oxley v Koitka).
[2] Cooper & Oxley v Koitka, [10].
[3] Cooper & Oxley v Koitka, [82].
[4] Cooper & Oxley v Koitka, [55].
[5] Cooper & Oxley v Koitka, [74].
[6] Cooper & Oxley v Koitka, [10].
[7] Cooper & Oxley v Koitka, [68]-[69].
[8] Cooper & Oxley v Koitka, [77].
[9] Cooper & Oxley v Koitka, [78].
[10] Cooper & Oxley v Koitka, [80], [82].
[11] Cooper & Oxley v Koitka, [84].
[12] Cooper & Oxley v Koitka, [85].
[13] Cooper & Oxley v Koitka, [12].
[14] Cooper & Oxley v Koitka, [94], [99].
[15] Cooper & Oxley’s argument in respect of Caledonia’s entitlements after termination for convenience became largely irrelevant once it accepted that its interpretation of cl 36.8(b) of the Subcontract would have the effect of modifying or excluding Caledonia’s SOPA rights, and was probably unenforceable pursuant to s 111 of the Building and Construction Industry (Security of Payment) Act 2021 (WA). Although not required to decide the issue, in obiter Lemonis J indicated he agreed with this view – see [103].
[16] Cooper & Oxley v Koitka, [94]-[98].
[17] Cooper & Oxley v Koitka, [100].
[18] Cooper & Oxley v Koitka, [109].
[19] [2025] NSWCA 49 [150] (Martinus v Qube (No. 2)).
[20] Cooper & Oxley v Koitka, [150]-[158].
[21] Cooper & Oxley v Koitka, [136].
[22] Cooper & Oxley v Koitka, [143].
[23] Cooper & Oxley v Koitka, [137], [143].
[24] Cooper & Oxley v Koitka, [144].
[25] Cooper & Oxley v Koitka, [146].
[26] Cooper & Oxley v Koitka, [159]-[161].
[27] Cooper & Oxley v Koitka, [164].
[28] Cooper & Oxley v Koitka, [163].
[29] Cooper & Oxley v Koitka, [41]-[42], citing Perrinepod Pty Ltd v Georgiou Building Pty Ltd [2011] WASCA 217 and Probuild Constructions (Aust) Pty Ltd v Shade Systems Pty Ltd [2018] HCA 4.
[30] Cooper & Oxley v Koitka, [44], quoting Total Eden Pty Ltd v Charteris [2018] WASC 60 (Total Eden). See also Acciona Agua Australia Pty Ltd v Monadelphous Engineering Pty Ltd (2020) QR 410, [35] (Acciona Agua).
[31] Cooper & Oxley v Koitka, [43], quoting Minister for Immigration and Multicultural Affairs v Yusuf [2001] HCA 30.
[32] Cooper & Oxley v Koitka, [45]-[46], quoting Total Eden. See also Ceerose Pty Ltd v A-Civil Aust Pty Ltd (2023) 112 NSWLR 225, [75]-[77] (Ceerose) – notably, this seminal case is not referenced in the Cooper & Oxley v Koitka judgment.
[33] Cooper & Oxley v Koitka, [47]-[49]. See also Acciona Agua, [36].
[34] Cooper & Oxley v Koitka, [47]. See also Ceerose, [52].
[35] Cooper & Oxley v Koitka, [48].
[36] Martinus v Qube (No. 2), [49].
[37] Cooper & Oxley v Koitka, [137].
[38] Cooper & Oxley v Koitka, [137].
[39] Bega Valley Shire Council v Kenpass Pty Ltd [2024] NSWSC 399 [52] (Bega).
[40] Icon Co (NSW) Pty Ltd v Australia Avenue Developments Pty Ltd [2018] NSWCA 339 [19] approved in Bega, [50]-[52].
[41] Cooper & Oxley v Koitka, [92].
[42] Cooper & Oxley v Koitka, [144]-[146].
[43] Ceerose, [62],[66].
[44] See above n 32.
[45] Payne JA, Ward ACJ and Basten AJA agreeing.
[46] Ceerose, [64].
[47] Ceerose, [63]-[65].
[48] Ceerose, [66].
[49] Ceerose, [66].