Assessing payment claims and getting the payment schedule right under WA’s Security of Payment Act

Progress payments are the lifeblood of a construction project. For principals and head contractors, assessing payment claims properly protects against overpayment. It also avoids the very real risk of becoming liable for the full amount claimed under the Building and Construction Industry (Security of Payment) Act 2021 (WA) (SOPA).

This article covers how payment claims are assessed under contracts based on AS 2124-1992 and AS 4000-1997, and how to give a valid payment schedule under SOPA.

Key takeaways

• There are two regimes running side by side. The contract sets out how claims are certified, while SOPA sets a separate, strict deadline for responding to a payment claim.

• Respond within 15 business days. Under SOPA, a respondent that does not give a payment schedule in time becomes liable for the full claimed amount.

• Put every reason in the schedule. Reasons for withholding payment that are not in the payment schedule cannot be raised later in adjudication.

• Enforce preconditions to payment from the start. Raising them for the first time halfway through a project invites waiver arguments.

• A payment certificate can double as a payment schedule, provided it is given on time, by someone authorised, and contains what SOPA requires.

Assessing the claim under the contract

Under most standard-form contracts, the contractor submits progress claims to the superintendent at the times set out in the contract, usually monthly. Under AS 2124, the claim should include the value of work carried out to date and all other amounts then due, such as variations and delay costs.

The superintendent then has to work out what is actually due. That involves two questions.

1. Has the work been done, and done properly? Check that the work claimed has been performed in accordance with the contract, and whether there are any defects.

2. What is it worth? Use the valuation method the contract requires. That may be rates in a bill of quantities, a percentage-complete assessment of a lump sum, or milestone payments. Be consistent from the first claim. Contractors naturally want strong early cash flow, and principals want to pay only for work actually done. Unless the contract says otherwise, the principal is generally not obliged to pay for unfixed plant or materials not yet incorporated into the works.

Preconditions to payment

Contracts commonly make payment conditional on things such as providing security, evidence of insurance, a tax invoice, or a statutory declaration that workers and subcontractors have been paid. Apply these from the first claim. If early claims are paid without them, the contractor is likely to argue that the requirement has been waived when it is later raised.

Requesting further information

The contractor's claim should be supported by evidence of the amount claimed and any information the superintendent reasonably requires. What is reasonable depends on the circumstances. It might include photographs of remote works, daywork sheets, or a breakdown of rates and quantities in a schedule of rates contract. It would rarely extend to the contractor's internal accounts, every invoice it has paid, or its profit margins. If you know you will need particular information, say so in the contract documents.

Ask for further information early. Requesting it does not stop the clock, so the superintendent should still issue an assessment on time, explaining what cannot be assessed and why.

Issuing the payment certificate

Under AS 2124, the superintendent must issue a payment certificate within 14 days of receiving the claim. The certificate should show:

• the value of work carried out to date

• amounts previously paid

• other amounts due between the parties

• retention moneys held and to be deducted

• the balance due, with reasons if it differs from the claim.

A template agreed at the start of the project makes this easier for everyone. Payments are on account only, and errors in earlier certificates can be corrected in later ones. Commercially, though, it matters who is holding the cash in the meantime. The superintendent can also issue a certificate even if no claim is made.

Responding under SOPA: the payment schedule

SOPA operates alongside the contract and gives contractors a statutory right to progress payments. A payment claim under SOPA must state that it is made under the Act (s 24). Once one is received, the respondent has a short, strict window to respond.

Timing

A payment schedule must be given within 15 business days after the payment claim is made, or earlier if the contract requires (s 25). Business days exclude weekends, public holidays and the period from 22 December to 10 January. Note that the contract's 14-day certification period (in calendar days) may be shorter than the SOPA deadline, and the earlier deadline applies.

If no payment schedule is given in time, the respondent becomes liable to pay the full claimed amount on the due date (s 26). It also loses the right to lodge an adjudication response and to seek review of the determination.

Content

A payment schedule must (s 25):

• be in writing, and in the approved form (if any)

• identify the payment claim it responds to

• state the amount the respondent proposes to pay, or that it proposes to pay nothing

• if less than the claimed amount, explain why, including the reasons for withholding any payment.

Get the reasons right first time. Under s 34(3), the respondent cannot include in its adjudication response any reason for withholding payment that was not in the payment schedule. Identify every defect, set-off, backcharge, liquidated damages claim and amount already paid, with enough detail for the claimant and an adjudicator to understand it. In Cooper & Oxley Group Pty Ltd v Koitka [2026] WASC 4, the Supreme Court stressed the importance of clearly identifying set-offs in the payment schedule.

Can the superintendent's certificate be the payment schedule?

Often, yes. SOPA treats a document given by a party's agent as given by that party (s 113). A superintendent's payment certificate can therefore operate as a payment schedule, provided the superintendent is authorised to respond on the principal's behalf, and the certificate is given within the SOPA timeframe and contains everything s 25 requires. Courts in other states have accepted this in appropriate cases (for example, Bucklands Convalescent Hospital v Taylor Projects Group Pty Ltd [2007] NSWSC 1514).

The safer course is to make the certificate expressly state that it is also a payment schedule under SOPA, or to issue a separate payment schedule at the same time. Do not assume that a certificate prepared only to satisfy the contract will also satisfy the Act.

Practical tips

• Diarise the SOPA deadline as soon as any claim arrives, and treat every claim as a potential SOPA claim.

• Check service carefully. An emailed claim may be "made" when it can be retrieved at the nominated address, even on a weekend (Co-Operative Bulk Handling Ltd v Martinus Rail Pty Ltd [2026] WASCA 82).

• Respond even if you need more information. Give a schedule with your best assessment and reasons, rather than none at all.

• Keep the superintendent out of the adjudication itself. The superintendent's role is to assess and certify. Advocacy in an adjudication is for the principal and its advisers.

How we can help

Lang Litigation and Construction Law advises principals, head contractors and subcontractors on payment claims, payment certificates and payment schedules, and acts in adjudications and enforcement proceedings under the Building and Construction Industry (Security of Payment) Act 2021 (WA). If you have received a payment claim and are unsure how to respond, contact us promptly. Strict time limits apply.

This article is general information only and is not legal advice. You should seek specific advice about your circumstances.