Payment certificates under NEC3 and NEC4

Payment under the NEC Engineering and Construction Contract runs to a clock, not to an invoice. Get the assessment dates, the build-up of the amount due and the certification deadlines right, and cash flows. Miss them, and — under NEC4 especially — silence has a price.

Section 5 of the ECC (clauses 50 to 53) governs how much the Contractor is paid and when. It is one of the most heavily used parts of the contract on any South African project, yet it is also one of the most misunderstood — partly because NEC3 and NEC4 take genuinely different starting points. This guide sets out how assessment works under both editions, where they diverge, and what that means in practice for quantity surveyors, commercial managers and Project Managers on roads, water, energy and building works.

Assessment dates: the heartbeat of the payment cycle

Everything in section 5 hangs off the assessment date. The first assessment date is set by reference to a starting date and then recurs at the interval stated in the Contract Data — for most projects that is monthly, which is why teams talk about the "monthly payment cycle". The Contract Data fixes both the starting point and the interval, so the rhythm of the project is agreed up front rather than improvised.

Assessment dates do not only fall at the regular interval, though. The contract also defines further assessment dates at particular events — for example, around Completion and at the points required to clear the final account. The important discipline is that an assessment is made at each assessment date: it is a snapshot of value as at that date, not a running negotiation that drifts week to week.

What the amount due is actually made up of

At each assessment date the amount due is calculated, and the structure is the same in NEC3 and NEC4. The amount due is:

• the Price for Work Done to Date — the value of work properly completed, assessed according to the main Option (for example, the activities completed under an Option A activity schedule, or the Defined Cost plus Fee under the cost-based Options); plus
• other amounts to be paid to the Contractor — sums the contract requires to be added at that date; less
• amounts to be paid by or retained from the Contractor — including any retention held under the relevant secondary Option, and other deductions the contract allows.

The "Price for Work Done to Date" is a defined term and its meaning shifts with the pricing Option, so a payment assessment can never be done properly without knowing which main Option the contract uses. That is the single most common source of error we see: applying a cost-reimbursable mindset to an activity-schedule contract, or vice versa.

Under NEC, you are not paid for the work you have done — you are paid for the Price for Work Done to Date. The wording is deliberate, and the difference is exactly the discipline the contract is enforcing.

The headline difference: who holds the initiative

This is where NEC3 and NEC4 part company, and it is the change most likely to catch out a team migrating between editions.

NEC3 — the Project Manager drives it

Under NEC3, the Project Manager assesses the amount due at each assessment date and certifies payment. The initiative sits with the Project Manager. The Contractor will of course submit supporting information, but the contractual act of assessment is the Project Manager's, with or without a formal application from the Contractor. If the Contractor disagrees, its route is to challenge the assessment — not to rely on a figure it submitted.

NEC4 — the Contractor applies first

NEC4 flips the default. The Contractor submits an application for payment on or before each assessment date (clause 50.2), setting out the amount it considers due and how it has been assessed. The Project Manager then assesses the amount due (clause 50.4). The sting is in the tail: if the Contractor has made an application and the Project Manager does not certify a payment when one is required, the amount the Contractor applied for can become the amount due.

That single change re-balances the relationship. Under NEC4 the Contractor must prepare a properly substantiated application every period — vague or unsupported applications are a gift to the Project Manager's own assessment — and the Project Manager must respond on time, because failing to certify no longer simply delays the conversation; it can hand the Contractor the figure it claimed.

Certifying and paying: the clock in clause 51

Once the amount due is assessed, two deadlines run from the assessment date. The Project Manager certifies a payment within one week of each assessment date (clause 51.1). Payment is then made within three weeks of the assessment date — or within a different period if a different period is stated in the Contract Data (clause 51.2). On South African projects it is common for the Contract Data, or a Z-clause, to set a payment period that suits the Client's own treasury or grant-funding cycle, so always check the actual figure rather than assuming three weeks.

The deadlines run from the assessment date, not from the date the certificate happens to be issued. A Project Manager who certifies late does not push out the payment deadline; the payment window keeps counting from the assessment date regardless.

If a payment is late — paid after the date by which it should have been paid — interest is due on the overdue amount under clause 51. Interest runs from the date the payment should have been made until the date it is actually made, at the interest rate stated in the Contract Data, compounded. This applies to a correction of an earlier assessment too: if a later assessment shows that an earlier one underpaid the Contractor, interest is payable on the difference. Interest is not a penalty the Contractor has to claim as a dispute — it is an automatic entitlement built into the payment mechanism.

Retention and the secondary Options

Retention is not in the core clauses; it is a secondary Option that the parties choose to include. Where secondary Option X16 applies, a percentage is retained from amounts due up to a stated retention free amount, and the contract sets out how and when the retention is released — typically reducing at Completion and being released after the defects are corrected. Because retention is an "amount retained from the Contractor", it sits squarely in the build-up of the amount due described above, reducing what is paid in each period until it is released.

Other secondary Options can also touch payment — for example advanced payment provisions, or price adjustment for inflation under the relevant Option. The practical point is that the assessment is only correct if every applicable secondary Option has been applied in the right order: value the work, add the additions, then apply retention and any other deductions.

South African overlays: statutory provisions and Z-clauses

The ECC was drafted for international use, so local payment regimes are layered on top through the Contract Data and Z-clauses rather than being part of the core wording. In the United Kingdom, secondary Option Y(UK)2 imports the statutory payment and adjudication provisions of the Housing Grants, Construction and Regeneration Act; that exact Option is UK-specific, but it is a useful reminder that statutory or policy payment rules frequently modify the standard timing.

In South Africa, watch for:

1. Amended payment periods. Public bodies and state-owned entities often impose their own payment terms via the Contract Data or a Z-clause, replacing the standard three-week period — and any supply-chain or sub-contract payment obligations that flow down from them.
2. Procurement and governance overlays. Funding conditions, National Treasury requirements and entity-specific procurement rules can add steps or documentation before a certified amount is actually released.
3. Z-clause modifications generally. Z-clauses can change almost anything in section 5 — interest rates, retention, the consequences of late certification — so the contract as amended, not the textbook NEC, is what governs.

With NEC, the danger is reading the standard clause and forgetting the Z-clause. On a South African public contract, the amended payment period in the Contract Data is the one that actually pays the bills.

Getting paid, and paying, on time

Section 5 is mechanical by design. The amount due is a defined calculation, the deadlines are fixed periods running from a known date, and — particularly under NEC4 — the consequences of inaction are written into the contract. None of that is hard in principle. What makes payment go wrong in practice is administration: an application that misses the assessment date, a certificate issued a week late, retention applied to the wrong base, or an amended payment period that nobody flagged. Spreadsheets and email threads were never a safe place to track that, and under NEC4's application-driven rules the cost of losing track is higher than ever.