NZS 3915 vs 3910: When the Client Is Also the Certifier (NZ)

Steve Parker
4 days ago
9 min read

NZS 3915 vs 3910 explained: 3910 has an independent certifier, 3915 has none — the principal certifies its own job. What that means for NZ contractors.

By Steve Parker · Trueworks · NZ construction estimation · 8 min

The two contracts read almost identically. The single biggest difference is invisible until something goes wrong: under NZS 3915 there is no independent umpire — the party paying you also decides what you get paid.

What you'll learn

The one structural difference between NZS 3910 and NZS 3915 — and why it matters more than any clause
Why a principal might choose 3915, and what that choice costs the contractor
How disputes actually get resolved when there is no neutral certifier
When each contract is genuinely the right fit

Quick answer: NZS 3910 is the New Zealand construct-only standard contract that appoints an Engineer to the Contract — in the 2023 edition split into a Contract Administrator and an Independent Certifier — who must assess payments, variations and extensions of time independently and impartially. NZS 3915 is the same contract with no Engineer: the Principal administers the job through a Principal's Representative who is under no obligation to act independently, impartially or fairly. So under 3915 the party paying you is also the party certifying what you are owed. That removes the neutral arbiter, which is why disputes under 3915 lean heavily on mediation and Construction Contracts Act 2002 adjudication.

What is NZS 3915, and how is it different from NZS 3910?

Both are New Zealand standard conditions of contract for construct-only work — the same family, drafted to sit alongside each other. Side by side, the clause numbering, payment regime, variation rules and time provisions look nearly identical. You could read most of NZS 3915 and never notice it is a different document.

The difference sits in one role. NZS 3910 appoints an Engineer to the Contract who values the work, certifies progress payments under §12, prices variations under §14, and decides extensions of time under §10. The 2023 edition split that combined role in two: a Contract Administrator, who is openly the Principal's agent and runs the contract, and an Independent Certifier, whose job is to assess payment claims, valuations and EOT entitlements impartially. The split was deliberate — it separated "running the job for the client" from "deciding who is right".

NZS 3915 deletes that independent function entirely. There is no Engineer and no Independent Certifier. The Principal administers the contract directly through a Principal's Representative — and the contract does not require that representative to act independently, impartially or fairly. They are the Principal's person, certifying the Principal's payments, on the Principal's job.

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Why this single change matters more than any clause

On a construction contract, somebody has to be the decision-maker in the gaps. Was that extra excavation a variation or part of the original scope? Is the contractor entitled to three weeks for the wet-weather delay, or one? Under NZS 3910, those calls are meant to be made by someone with a contractual duty to be even-handed — the Independent Certifier — even though that person is paid by the Principal.

Under NZS 3915, the same calls are made by the Principal's Representative, who has no such duty. The structural risk is plain: the party that benefits from paying you less is the party deciding how much you are owed.

This bites hardest on the things that are most arguable:

Variations. Under §14 the valuation hierarchy runs agreed price, then contract rates, then reasonable rates, then daywork. Plenty of room for judgement — and under 3915 that judgement belongs to the side that pays.
Extensions of time. Under §10 an EOT turns on causation and reasonableness. A self-interested assessor and an impartial one can land a long way apart on the same facts.
Progress payments. Under §12 someone decides what proportion of the work is complete and properly claimable. Small percentage shifts on a large claim carry real value.

None of this means a Principal's Representative will act in bad faith — many are scrupulous. But the contract removes the safeguard and relies on goodwill, and goodwill is exactly what evaporates when a job goes sideways.

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Why would a principal choose NZS 3915?

Two honest reasons: cost and control.

Cost. An Independent Certifier is a paid, named role — usually an engineer or quantity surveyor engaged specifically to certify. On smaller jobs that fee is a meaningful slice of the budget, and NZS 3915 lets the Principal self-administer and avoid it. This is why 3915 is more common on smaller and residential-scale work around Auckland — a single-dwelling build, a small commercial fit-out, a developer doing repeat work who already runs their own project management.

Control. A principal who has been on the wrong end of a generous certifier may prefer to keep certification in-house. That is a legitimate commercial preference. The contractor just needs to see it for what it is — and price the risk accordingly.

The honest nuance on NZS 3910: independent on paper isn't always independent in practice

It would be neat to say NZS 3910 solves the problem and 3915 creates it. The reality is messier, and any contractor signing a 3910 should know it.

The Independent Certifier under 3910 is paid by the Principal and is frequently from the same firm that produced the design. When that firm's drawings turn out to be 60–70% complete at tender — common on New Zealand fixed-price jobs — many of the variations and delays flow directly from the gaps in that design. The certifier is then assessing claims that, in part, arise from its own incomplete documentation. The duty to be impartial is real and enforceable, but it sits in genuine tension with the commercial relationship. Independence on the page is not always independence in the room. NZS 3910 gives you a far better starting position than 3915 — it does not guarantee a perfectly neutral one.

So how do disputes actually get resolved?

This is where the gap between the two contracts narrows, because New Zealand has a statutory backstop that does not care which contract you signed.

Under NZS 3910, the contract's own §13 dispute machinery — engineer/certifier determination, then mediation, then adjudication or arbitration — gives you internal steps before you go external. Our breakdown of how NZS 3910 §13 disputes are resolved walks through that ladder.

Under NZS 3915, with no independent certifier to make a first-instance call, disputes tend to jump straight to mediation and then to the real equaliser: adjudication under the Construction Contracts Act 2002. The CCA applies regardless of whether you used 3910, 3915 or no standard form at all. Two parts of it matter enormously when your counterparty is also your certifier:

The payment-claim / payment-schedule regime. If you serve a compliant payment claim and the Principal does not issue a compliant payment schedule in time, they can become liable for the full claimed amount — a powerful lever precisely because it does not depend on anyone certifying in your favour.
Statutory adjudication. A fast route to an independent adjudicator — often the first time a genuinely neutral person looks at the merits of a 3915 job. Pay-when-paid clauses are void under the Act, and on commercial contracts the Retention Money Amendment Act 2023 (in force 5 October 2023) requires retentions to be held on trust in a separate complying bank account — protections that exist no matter how conflicted the contract administration is.

The practical takeaway: NZS 3915 strips out the contractual umpire, but it cannot strip out the statutory one. Adjudication is what stands between a contractor and a counterparty marking its own homework.

NZS 3910 vs NZS 3915 at a glance

Who administers the contract — NZS 3910: Contract Administrator (the Principal's agent, 2023 edition). NZS 3915: Principal's Representative.
Who certifies payments, variations and EOTs — NZS 3910: Independent Certifier (2023 edition). NZS 3915: Principal's Representative.
Independence and impartiality obligation — NZS 3910: yes, the certifier must act independently and impartially. NZS 3915: no, the representative is not required to be independent, impartial or fair.
First-instance dispute call — NZS 3910: engineer or certifier determination, then the §13 ladder. NZS 3915: none internally — it leans on mediation and CCA 2002 adjudication.
Typical use — NZS 3910: larger or commercial work where neutral certification is expected. NZS 3915: smaller, residential or repeat work with principal-controlled administration.

What to check before you sign

Confirm which contract it actually is. Do not assume 3910. Check the cover page and the conditions — 3910 and 3915 look near-identical and the difference is easy to miss.
If it is 3915, identify the Principal's Representative and accept that they are not neutral. Plan your contract administration around the absence of an independent certifier, not around hoping one shows up.
Tighten your scope and qualifications at tender. Without a neutral certifier, ambiguity is decided against you. Tag out ground risk, provisional sums and incomplete design explicitly — vague scope is far more dangerous under 3915.
Run a disciplined CCA payment-claim process from day one. Compliant payment claims and tight timing are your strongest protection when the certifier is your counterparty.
Document everything contemporaneously. Photos, daily records, written variation and EOT notices within the §10 / §14 timeframes. If it goes to adjudication, the contractor with the paper trail wins.
Price the risk. A job under 3915 with thin design carries more certification risk than the same job under 3910. That belongs in your margin.

This is general information, not legal advice — get advice on your specific contract.

FAQ — NZS 3915 vs NZS 3910

Q1: What is the main difference between NZS 3910 and NZS 3915? NZS 3910 appoints an independent certifier (an Engineer to the Contract, split in the 2023 edition into a Contract Administrator and an Independent Certifier) to assess payments, variations and extensions of time impartially. NZS 3915 has no such role — the Principal certifies its own job through a Principal's Representative who is not required to be independent or impartial.

Q2: What is NZS 3915 used for? NZS 3915 is the New Zealand standard construct-only contract for jobs where no Engineer to the Contract is appointed. It is most common on smaller, residential or repeat work where the principal wants to self-administer and avoid the cost of an independent certifier.

Q3: Is NZS 3915 bad for contractors? Not automatically, but it carries more risk. Because the Principal's Representative both pays and certifies, valuations, variation pricing and EOTs are decided by your counterparty rather than a neutral party. Tight scope, disciplined Construction Contracts Act 2002 payment claims and contemporaneous records are essential to manage that risk.

Q4: Who is the Principal's Representative under NZS 3915? The Principal's Representative is the person the Principal nominates to administer the contract and certify payments, variations and time claims. Unlike the Independent Certifier under NZS 3910, they act for the Principal and have no contractual duty to be independent, impartial or fair.

Q5: How are disputes resolved under NZS 3915 if there is no engineer? With no internal independent certifier, disputes lean on mediation and then statutory adjudication under the Construction Contracts Act 2002. Adjudication gives both parties access to an independent decision-maker regardless of which standard contract was used, which is why it is often the first genuinely neutral assessment on a 3915 job.

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About Trueworks

Trueworks is built by Steve Parker — 20 years on the analytical side of NZ construction. Variation reviews, contract advisory, programme review, and AI-augmented document workflows. Trueworks is the productisation of that practice for builders: same defensible analysis, at a price and pace a NZ builder can actually use.

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