Under the NEC4 Engineering and Construction Contract (ECC), the main option determines the basis of payment. Options A and B value completed priced work, while C, D and E use Defined Cost plus the Fee. Option F has a separate mechanism for its management-contract arrangement.
The Contractor applies for payment and the Project Manager assesses the amount due and certifies payment. The Party owing payment must then pay the certified amount within the required period. On an Australian project, these procedures must be read alongside the applicable security of payment legislation and Y(Aus)1 where selected. The contract structure and selected options establish which provisions the team needs to apply.
The ECC provisions described here are those of the June 2017 edition incorporating the January 2023 amendments. The Australian Y provisions are the November 2024 ECC Y(Aus)1 wording. The applicable legislation, Contract Data and any project amendments need to be checked before applying those provisions.
On the fictional Ironbark Recycled Water Scheme, a regional Australian water utility is procuring a pipeline, pumping station and balancing tank under Option C. The scheme will supply recycled water from an existing treatment plant to an industrial estate, with the plant remaining operational during construction and connection.
Payment applications and assessment dates
Under standard clause 50.1, the Project Manager chooses the first assessment date to suit the Parties’ procedures. It must be no later than the assessment interval after the starting date. Assessments then occur at the end of each interval until the Supervisor issues the Defects Certificate or the Project Manager issues a termination certificate. Completion of construction does not end periodic assessment.
Before each assessment date, the Contractor submits an application showing the amount it considers due, how it has calculated that amount and the information required by Scope. The Project Manager considers a timely application but makes its own assessment of the amount due.
At Ironbark, the Contractor would assemble the cost records and forecast payments, calculate the Fee and identify any additions or deductions. For a leaking-joint investigation and repair, the records would need to show what work was done and how its cost should be treated under the Defined Cost and Disallowed Cost rules. Allocating an invoice to Ironbark’s project code does not, by itself, make it payable.
If an application is absent or late, standard clause 50.4 limits the amount due to the lower of the amount the Project Manager would otherwise assess and the previous amount due. There is no increase for that assessment, although a reduction can still result in payment back to the Client. On an Australian project, this rule must be read with Y(Aus)1 and the applicable legislation before it is applied to a statutory payment claim.
Assessing and paying the amount due
The amount due is cumulative. It includes the Price for Work Done to Date and other amounts payable to the Contractor, less amounts payable by or retained from it. Price for Work Done to Date is a defined term, calculated differently under the main options. It may differ from the value of physical progress shown in a site report.
Under clause 51.1, the first payment equals the amount due, while later payments are the change since the previous assessment. For example, if Ironbark’s current amount due were $1.2 million and the previous amount due $1 million, the new payment would be $200,000 before any tax to be added.
The standard certificate is issued within one week of the assessment date and includes details of the assessment. Certified payment is made within three weeks of that date unless Contract Data states another period. The period runs from assessment, not from completion of the Client’s internal approval process. Y(Aus)1 changes some of these periods and the events from which they run.
Clause 50.6 requires an incorrect assessment to be corrected in a later certificate. Late payment attracts interest under clause 51.2, including where payment is late because a required certificate was not issued. Clause 51.3 also provides interest on correcting amounts in specified circumstances, including mistakes, compensation events and unnecessary testing delays caused by the Supervisor. Interest is calculated daily at the contractual rate and compounded annually, subject to any overriding statutory requirements.
Payment is in the currency of the contract unless the contract provides otherwise. Under clause 51.5, tax which the law requires one Party to pay the other is added. The payment calculation and tax documentation should be coordinated so that internal invoice processing does not delay payment beyond the due date.
Withholding payment for the first programme
Where no programme is identified in Contract Data, clause 50.5 retains one quarter of the Price for Work Done to Date until the Contractor submits its first programme for acceptance containing the required information. The retention is calculated against that defined amount. It is not a discretionary deduction from an invoice.
The retained amount is released through the cumulative payment calculation once the Contractor submits a programme containing the required information, without waiting for Project Manager acceptance. The provision does not apply where a programme is identified in Contract Data, nor does it give the Project Manager a general power to retain the quarter for missing later revisions. Ironbark’s programme obligations still need to be administered separately from this payment provision.
What earns payment under Options A to F
Option A completed activities
Under Option A, payment is based on the Activity Schedule prices for completed activities and completed groups of activities. For payment purposes, an activity is complete when it has no notified Defects whose correction will delay following work. An incomplete activity does not earn a percentage of its price under that mechanism. A large activity covering installation and testing can therefore defer payment until both are complete. The Activity Schedule needs to reflect recognisable stages of the work if it is to support the intended cash flow.
If Ironbark’s pipeline were instead procured under Option A, an activity covering a complete section and its pressure test could remain unpaid until the required work was complete. Dividing that work into appropriately defined activities would change when payment could be earned, without changing the requirements in Scope.
Option B measured work
Option B values the completed quantity for each Bill of Quantities item at its rate, together with the proportion of each lump sum corresponding to completed work. Its definition of completed work also addresses notified Defects whose correction will delay following work. If similar pipeline work were procured under B rather than Ironbark’s Option C, the completed measured quantity would enter the valuation. Separate provisions address quantity differences which satisfy the conditions for a compensation event and qualifying mistakes in the Bill. A quantity difference does not, by itself, justify changing a rate.
Options C and D target contracts
Options C and D pay Defined Cost plus the Fee. Their Price for Work Done to Date includes Defined Cost which the Project Manager forecasts the Contractor will have paid before the next assessment date. Ironbark’s assessment therefore considers supported payments expected within that period as well as payments already made. Completing an Activity Schedule item is not the trigger for paying eligible cost.
The Activity Schedule under C and the Bill of Quantities under D have a separate role in establishing the target. C uses the total of the Prices. D uses its separately defined Total of the Prices for sharing, reflecting completed measured quantities and the relevant lump sums. Periodic payment continues through the cost mechanism. Reaching the target does not automatically stop further payment.
At Completion of the whole works, the Project Manager makes a preliminary assessment of the Contractor’s share using forecast final figures and includes it in the following amount due. The final share assessment uses the final figures. Clause 54 provides for the Contractor to receive its specified share of a saving or pay its share of an excess. Eligible repair costs could therefore enter Ironbark’s payment assessment without increasing the target, while still affecting its eventual share.
On Ironbark, a failed test does not, by itself, establish whether the associated cost is payable. The quality and Defect provisions govern correction, while the cost provisions govern eligibility for payment. The Supervisor has no general power to approve or deduct costs.
Option E cost reimbursable payment
Option E is cost reimbursable. It uses Defined Cost plus the Fee for payment, without C and D’s target-sharing mechanism. The requirements for eligible cost, Disallowed Cost and supporting records still apply.
Option F management contracts
Option F values subcontracted work through payments due under subcontracts, adjusted to avoid duplicate payment or retention. It uses prices for the Contractor’s own work identified in Contract Data, less its separately defined Disallowed Cost, with the Fee added. The Project Manager needs to apply F’s payment provisions rather than assess it through Option E’s cost schedule.
Other amounts affecting payment
The assessment also includes amounts payable by the Contractor for uncorrected Defects or failure to meet a Key Date, where the contract requires them. Selected secondary options can add to, or deduct from, the amount due. None is assumed to apply to Ironbark.
X14 provides an advance payment. It is included at the first assessment or the next assessment after receipt of a required bond. Repayment starts after the period stated in Contract Data and continues until the advance has been repaid.
X16 provides retention above the retention-free amount until the earlier of Completion or takeover of the whole works. The retained amount is halved in the assessment following Completion of the whole works, or earlier takeover of the whole works. No retention is made in assessments after the Defects Certificate is due. A permitted or agreed retention bond can replace the cash retention, releasing the money in the next assessment. X16 is not used with Option F.
X1 provides price adjustment for inflation under A to D. It adjusts amounts due under A and B, but adjusts the target under C and D. X3 provides multiple currencies under A and B, subject to the maximum amounts in Contract Data. C to F have their own main-option provisions for Defined Cost payments made in other currencies. The Fee, and the share under C or D, are calculated using the stated exchange rates and paid in the currency of the contract.
Where selected, X6 adds a daily bonus from the earlier of Completion or takeover to the Completion Date. X7 provides delay damages until the earliest of Completion, takeover or termination, with repayment and interest if a later Completion Date establishes an overpayment. X17 deals with specified low performance shown by a Defect in the Defects Certificate. X20 can add incentive payments when its targets are achieved, but cannot be used with X12.
X12 provides partnering incentives and X29 uses Performance Table payments. Under X21, agreed whole-life-cost proposals can change the Prices. X22, available only with C and E, changes Stage Two pricing arrangements and adds a budget incentive. The conditions for each selected option and the project’s Contract Data govern how it affects the assessment.
Implementation of a compensation event changes the Prices and relevant dates under clause 66. Under A or B, that changes the pricing documents used for valuation. Under C, it can change the target while eligible cost is paid through the cost mechanism. Submitting a quotation does not, by itself, make the quoted amount an additional payment.
Records and finalising Defined Cost
C, D and E require accounts of payments relating to Defined Cost, proof of payment, subcontract compensation event records and further records specified in Scope. F’s corresponding requirements focus on subcontract payments. The Project Manager can inspect the required accounts and records during working hours, so they need to be kept current for periodic assessments and the finalisation of cost.
For C to F, clause 50.9 allows the Contractor to notify that Defined Cost for a part of the works has been finalised and make the supporting records available. The Project Manager has thirteen weeks to accept it, request further records or notify errors. The Contractor provides further records or corrections within four weeks, followed by a four-week Project Manager response. Failure to decide within the applicable period causes that part of Defined Cost to be treated as correct. This closes the cost assessment for that part of the works, rather than replacing the final assessment of the amount due under the contract.
Australian security of payment and Y(Aus)1
Australian security of payment legislation applies independently of whether Y(Aus)1 is selected. The clause adapts the ECC’s procedures to local requirements, but its wording needs to be checked against current law. The November 2024 version revised the provisions for Western Australia; subsequent legislative amendments may require further changes to the payment arrangements.
Contract Data provides for the security of payment legislation to be identified, but that entry does not determine which Act applies. That is governed by the application provisions of the legislation, including where the work is carried out and the nature of the contract. The applicable Act may therefore differ from the one named in Contract Data. If a pipeline or other project crosses a state or territory boundary, more than one regime may apply to different parts of the work. The payment arrangements need to be checked against each regime that applies to the relevant work.
The Australian legislation and Y(Aus)1 material discussed here were reviewed on 20 October 2026. The ECC assessment procedure and the statutory payment process need to be checked separately: compliance with one does not necessarily satisfy the other. Current legislation, commencement provisions and transitional rules must be checked for the particular contract.
The Y(Aus)1 Contract Data sets the assessment interval to monthly. New South Wales and Western Australia require an entry where the certification period differs from one week. Western Australia has registration-number entries for each Party where applicable and a change allowing a retention bond under X16. For Queensland commercial building contracts, the payment period is stated as two weeks after assessment. Each entry needs to be checked against the legislation applying to the project.
For the Australian Capital Territory (ACT), South Australia, Tasmania and Victoria, Y1.1 requires an application no more than one week before assessment. It links applications and certificates to statutory payment claims and payment schedules. It also deals with final claims and claim entitlements which existed at termination but had not been exercised. Its reference-date wording needs to be reconciled with current legislation, particularly in ACT and Victoria.
Y1.2 replaces clauses 50.1 to 50.4 for New South Wales and Western Australia. Assessment dates fall at month-end, but certification normally occurs within one week of application submission and payment within three weeks of submission. The standard restriction on increasing the amount due without a timely application is removed. Where payment is due back to the Client, the timing continues to run from the assessment date. Y1.2 also replaces the first sentences of clauses 51.1 and 51.2 and permits applications following termination. Its periods expressed in weeks must still be checked against statutory business-day limits.
Y1.3 provides Queensland’s payment-claim and payment-schedule arrangements, including final reference dates and post-termination applications. The Northern Territory is outside these jurisdiction-specific replacements, although the common Y provisions still apply. Its legislation uses prohibitions and, where relevant written terms are absent, implied contract terms. It should not be administered as though it had the same payment-schedule procedure as the eastern states.
Payment claims schedules and statutory time limits
Under Y1.6, a payment claim issued to the Project Manager is treated as issued to the Client for statutory purposes. The claim should identify the Client, describe the work and state the claimed amount, with any statutory endorsement required. New South Wales head-contractor claims also need the applicable supporting statement. Content and service must satisfy the legislation. The communication arrangements need to establish receipt and allow a response in time; uploading a document to a discussion folder does not establish compliant service.
A certificate intended to act as a payment schedule must identify the claim and scheduled amount, give the required reasons for any reduction or withholding, and be communicated in time on the Client’s behalf. The document must meet those statutory requirements regardless of its title. A later correction under the contract does not necessarily remedy an earlier statutory failure.
For ordinary non-residential head contracts, New South Wales generally requires payment within 15 business days of the claim and Western Australia within 20, unless the contract requires earlier payment. The respective schedule limits are 10 and 15 business days, or an earlier contractual period.
Western Australia’s 2021 Act generally applies to contracts entered into on or after 1 August 2022. Earlier contracts require the former regime to be checked. The published payment-claim template is recommended rather than mandatory, but the claimant must check whether any approved-form requirement applies when the claim is made.
ACT requires payment by the earlier of 15 business days after the claim and the contractual due date. In Queensland, a payment schedule is generally required within 15 business days or the earlier contractual period, unless the full amount is paid by the due date. Commercial building contracts have a maximum payment term of 15 business days from the claim.
South Australia generally allows 15 business days for a payment schedule, or an earlier contractual period. Tasmania’s ordinary commercial limit is the earlier of the contractual payment period and 10 business days. Its residential-owner provisions use a different test.
Victoria’s reforms took effect on 15 April 2026. They removed reference dates and excluded amounts, changed claim timing and capped contractual payment and security-release periods at 20 business days after service of the relevant claim. They also introduced a statutory process for claiming release of performance security. The reforms generally apply to existing contracts, subject to transitional exceptions including earlier claims and pending adjudications. The November 2024 Y wording needs to be reconciled with those requirements.
Northern Territory legislation limits contractual payment periods to 30 working days. Its implied notice-of-dispute and payment terms apply where the contract lacks the relevant written provisions, so a contract with its own payment procedure needs a different analysis from one which is silent.
South Australia’s regulations effective from 1 September 2026 retain exemptions from specified enforcement, adjudication and suspension provisions for certain Crown contracts exceeding $4 million excluding GST. They do not exclude the whole Act. Ironbark’s utility status and contract value are unspecified, so no exemption is assumed.
Definitions of business days and holiday exclusions differ between jurisdictions. Statutory interest may override a lower contractual rate, while the Northern Territory has its own interest provisions. When preparing and administering NEC4 in Australia, the team needs to calculate dates for each claim using the applicable law and contract.
Unpaid claims adjudication and suspension
An unpaid or reduced claim may give rise to statutory adjudication and recovery rights, subject to the jurisdiction’s conditions and deadlines. Under Y1.4, an application for statutory adjudication ends contractual adjudication of that payment-claim dispute. The statutory appointment and procedure then govern that dispute, without replacing every contractual dispute procedure for other issues.
Under Y1.5, exercising a statutory right to suspend performance is a compensation event, provided the statutory grounds and notice requirements are satisfied. A late certificate or disagreement about an assessment does not give an unrestricted right to stop work. At Ironbark, any valid suspension would also need to be managed around the operating treatment plant, without altering the legal conditions for exercising the right.
Final assessment and payment after termination
Under standard clause 53.1, the Project Manager assesses the final amount due and certifies any final payment within four weeks after the Defects Certificate, or thirteen weeks after a termination certificate. Final payment is due within three weeks of assessment unless Contract Data states another period. Y(Aus)1’s final-claim provisions and statutory timing must also be considered.
If the Project Manager does not assess in time, clause 53.2 allows the Contractor to issue its assessment to the Client, with details of the calculation. The Client’s agreement triggers the stated final-payment obligation. Silence does not amount to agreement, although the separate provisions on conclusivity still need to be considered.
An assessment issued within the contractual time can become conclusive under clause 53.3 unless challenged through the specified W1, W2 or W3 procedure. W1 and W2 require initial action within four weeks, followed by further steps and deadlines. W3 uses the Dispute Avoidance Board route. Clause 53.4 addresses agreements and decisions or recommendations not referred to the tribunal within four weeks. These procedures must be read with any applicable statutory payment rights; a general objection is not a substitute for taking the required action in time.
Payment after termination requires clause 93 and the Termination Table to be applied. The assessment includes the normal payment valuation, qualifying Plant and Materials, other costs incurred in expectation of completing the works and retained amounts, less any unrepaid advance. Further additions or deductions depend on the reason for termination, and main-option provisions affect valuation and target sharing. Termination neither makes the remaining contract price automatically payable nor permits a valid post-termination payment claim to be ignored.
At Ironbark, the Contractor’s applications and supporting records need to reach the Project Manager in time for a reasoned assessment. The payment record should allow both Parties to reconcile each assessment with the amounts actually paid, while the Client’s payment arrangements need to meet the due date, including any earlier date required by legislation.
