NEC4 Contract Data: Completing It Like a Pro
In NEC4 ECC, Contract Data Part One (Client) and Part Two (Contractor) are the control panel of the contract – if you fill every box deliberately, line up both parts, and avoid lazy defaults, the whole NEC4 “machine” runs smoother for everyone.
1 Why Contract Data secretly runs the whole job ⚙️
Imagine this: the project is in month 10, there’s been a big design change, and the Contractor suddenly claims a huge compensation event. The Project Manager says, “You’re out of time – you missed the 8-week notification bar under clause 61.3.” The Contractor fires back, “I didn’t even know we had 8 weeks, nobody explained it.”
Where does that clarity actually come from? Most of it lives in – or is driven by – the Contract Data.
In NEC4 ECC, Contract Data is where you:
- Switch on the Main Option (A–F) and all the relevant secondary options (X, Y, W).
- Fix the project-specific numbers: dates, time periods, reply times, programme update intervals, defects periods, payment cycles, limits of liability, fee percentages, etc.
- Tie together the other key documents: Scope, Site Information, pricing documents, and the initial risk / early warning items.
If you treat Contract Data as “just a form” and leave gaps, you don’t just have an untidy contract – you’re literally changing how compensation events, payments, time bars and liabilities work in practice. That’s why NEC authors and trainers keep repeating: completing Contract Data Parts One and Two properly is fundamental to contract success.
Treat each box in Contract Data as a deliberate setting on a control panel. If you don’t choose the setting consciously, the project may still run – but you’ve lost control over how it responds to change, risk and time.
2 Contract Data in one picture (Client vs Contractor) 📍
Here’s a simple mental model you can teach to your team:
Part One (Client) – “Here’s how we want to run this job.”
Part Two (Contractor) – “Here’s who we’ll use, how we’ll price it, and how we’ll deliver it.”
| Section / Item | Where? | Who completes? | Biggest risk if wrong or blank |
|---|---|---|---|
| Contract strategy (Options A–F, X/Y/W) | Part One – General | Client / Employer | Wrong pricing model, wrong risk split, wrong dispute route. |
| Parties & roles | Part One – General | Client | Notices mis-served, confusion about authority and decisions. |
| Key dates & time periods | Part One | Client | Time-bar fights; arguments about “late” replies and programmes. |
| Payment mechanics | Part One | Client | Cashflow shocks; non-compliant payment cycles. |
| Liabilities & insurance | Part One | Client | Uninsured risks; unintended unlimited liability. |
| Z clauses (bespoke conditions) | Part One (Z section) | Client + legal | Hidden risk shifts; clashes with NEC core clauses. |
| Pricing data (AS / BoQ / fee basis) | Part One + Pricing docs | Client prepares, Contractor prices | Holes in scope pricing; re-measure disputes. |
| Fee %, share ranges, Working Areas | Part Two | Contractor | Under- or over-recovery of Defined Cost under Options C–F. |
| Key People, programme reference | Part Two | Contractor | No realistic Accepted Programme; wrong people on paper. |
| Contractor’s assumptions & extras | Part Two / clarifications | Contractor | Surprise claims based on “hidden” assumptions. |
You want these two parts to tell one coherent story. If Part One says “Option C target contract with shared risk” but Part Two looks like a lump-sum Option A spreadsheet, you’ve got a problem before the first digger arrives.
3 Five “professional drafter” habits (before filling a single box)
Before anyone starts typing into the NEC templates, good practitioners quietly follow these habits. Think of them as a pre-flight checklist for Contract Data.
If you genuinely want the NEC default – write it down. No one on site will go hunting through the main ECC booklet, compare guidance notes, and then guess which default you “probably meant”.
- Period for reply – write “1 week” or “2 weeks”, don’t leave it empty and hope everyone remembers what NEC’s default behaviour is.
- Defects correction period – if you’re happy with the “standard” 52 weeks, write “52 weeks after Completion” so there’s no doubt.
Ask yourself: could a Site Engineer or Planner pick this up, find the period for reply, the payment cycle, and the programme frequency within 60 seconds?
If not, you’re still in “legal drafting” mode, not “project management” mode. NEC is designed as a project management contract, so your Contract Data should read like something a project manager can use day-to-day.
If the Scope says “payments monthly” but Contract Data says “assessment interval every four weeks”, which one wins? NEC deliberately does not include a strict document hierarchy, so you don’t want clashes.
Pro habit:
- Decide which document will hold each key number (often Contract Data).
- Make sure Scope and pricing documents refer to that number, instead of repeating it differently.
Every Z clause is a deliberate cut into a contract that’s already been balanced by NEC’s authors. Good drafters ask:
- “Is there an existing X/Y/W option that already does this?”
- “Are we changing the way compensation events, early warnings, or programmes work?”
If the answer is yes, you proceed with extreme caution – otherwise you risk breaking time bars, changing risk allocation unexpectedly, or creating contradictions.
Before signature, sit down with both parts side by side and ask:
- Do the dates, options, and pricing structures line up?
- Do the fees, Working Areas and target or lump-sum totals match the option we picked (A, C, D, etc.)?
CECA’s NEC4 bulletins repeatedly stress this: Part One and Part Two are both “very important documents that form part of the signed contract… any gaps could lead to ambiguity or uncertainty”.
Completing Contract Data Part One (Client side)
Lock in the shape of the deal, slowly and deliberately, before tenders go out.
Contract Data Part One is where the Client quietly fixes the deal’s DNA: options, roles, dates, payments, liabilities and early-warning “seeds”. Fill it slowly and properly, and the whole NEC4 machine runs smoother.
4 Completing Contract Data Part One (Client side) – slowly and properly
Let’s walk through Part One as if we’re filling it in together. Think of this as a slow, deliberate pass through the Client side of the form – not a rushed box-ticking exercise.
4.1 Contract strategy: locking in the “shape” of the deal
This is where you crystallise the decisions from your procurement strategy workshop. Before you even touch the boxes, be clear on: “What are we buying, how do we want to pay for it, and how do we want disputes to be handled?”
Main Option (A–F)
- Write the full name – for example, “Option A: Priced contract with activity schedule”.
- Immediately check: do we have an Activity Schedule (A/C) or Bill of Quantities (B/D) ready and properly referenced under Pricing Data? If not, stop and fix that before moving on.
Dispute resolution Option (W)
Choose W1 or W2 (or local equivalent) based on whether your jurisdiction has statutory adjudication. Record any details required: adjudicator nominating body, tribunal type, and any local requirements for adjudication or arbitration.
Secondary options (X and Y)
This is your toolkit for things like delay damages (X7), inflation (X1), retention (X16), performance bond (X13), limitation of liability (X18), and local law payment regimes (Y options).
- For each chosen option, check if it requires extra data – e.g. X7 (delay damages rate), X16 (retention percentage).
- Scan the Contract Data and confirm you haven’t left any of these numbers blank.
You tick X7 (delay damages) but forget to insert a rate.
Result? You’ve signalled that you want delay damages, but you haven’t told anyone how much. That’s an argument waiting to happen – fix it in Part One before tenders go out.
4.2 Parties, roles, and communication – the boring bits that matter
Here you pin down the basic identities and addresses that make the whole contract legally “connect”:
- The legal names of Client, Contractor, Project Manager, Supervisor (not just trading names).
- The addresses (including emails, if allowed) for formal communications.
- Any special communication systems – e.g. “All notifications under clause 13 are issued via [named platform]”.
Why is this not just admin? Because NEC is notice-heavy. Time bars (like the 8-week bar under clause 61.3 for some compensation events) only work if notices are properly sent and received.
If the Contract Data says “all notices by post to X address” but everyone starts using email, sooner or later someone will argue “your CE notification wasn’t valid”. Get this clear up front.
4.3 Dates, periods and time – where most silent traps live
This section sets the tempo of the contract. Sloppy numbers here can create “silent traps” that only appear in month 10, when it’s too late to fix cheaply.
Starting Date and Access Date(s)
- Starting Date – the formal contract start.
- Access Date(s) – when the Contractor actually gets on Site.
If you set an Access Date later than the Starting Date, you must ensure your programme and Completion Date allow for that. If you don’t, you’ve set the Contractor up to fail from day one.
Completion Date and Key Dates
- Completion Date – when the works as a whole must be complete.
- Key Dates – deadlines for particular parts, usually tied to functional milestones.
Check they are realistic compared with the Scope and any outline programme assumptions. If Key Dates are aggressive but not priced properly, you’ll see early compensation events.
Period for reply
NEC often assumes a default one-week period for replies to certain notices unless otherwise stated, but good practice is to state what you want in Contract Data.
Too short, and the Project Manager will technically be in breach constantly. Too long, and decisions drift.
Programme intervals
Under clause 32, the Contractor must submit revised programmes at intervals stated in Contract Data. Monthly works well for most projects; very fast-track jobs might need fortnightly updates.
Defects date and defects correction period(s)
The Defects date is when the “defects correction period” regime finishes (e.g. “52 weeks after Completion”). The defects correction period is how long the Contractor has to fix each notified Defect. You can set different periods for different things (e.g. 7 days for safety issues, 28 days for cosmetic issues).
What happens if you just accept defaults without thinking? You might unintentionally give the Contractor an extremely short correction period that doesn’t reflect reality, or tie yourself to very slow reply periods that clash with internal governance. The cure is simple: decide deliberately and write it down.
4.4 Payment mechanics: how money actually flows
In Contract Data Part One, you hard-code how cash moves. Contractors read this section with a highlighter in hand – and price risk accordingly.
Assessment intervals and dates
Choose the frequency (monthly, 4-weekly, etc.) and the assessment day. This controls when the Project Manager assesses the amount due under clause 50.
Final date for payment / payment cycle
These must comply with local law (for example, if a Y option implements statutory payment times). Check your in-house legal or local counsel if you’re unsure.
Retention (if X16 is used)
- Retention percentage and any cap.
- Release points – for example, half at Completion, half after the Defects date.
Advance payment (if X14 is used)
- Amount or percentage, and method of recovery (e.g. equal deductions from interim payments).
- If an advance payment bond is required, reference its form and amount here or in Z clauses.
Get this wrong and you’ll see serious cashflow stress. Contractors will price extra risk if payment terms are vague or apparently unfair.
4.5 Liabilities, caps and insurance – your risk “seat belt”
Here you set the protection levels for both sides. Treat this as the project’s risk seat belt – you hope you never need it, but you’ll be glad it’s there.
Limitation of liability (X18)
Decide whether overall liability is capped (for example, a multiple of the total of the Prices) and whether specific heads of loss are excluded or capped.
Insurance levels
State the minimum cover for:
- Public liability and employers’ liability.
- Professional indemnity (if there is Contractor design).
- Any project-specific insurances (e.g. marine cargo for imported plant).
Blanks here don’t mean “no risk” – they can mean unlimited liability or inadequate insurance, which is worse.
4.6 Additional compensation events and early warning “seeds”
Two powerful levers you get in Part One are additional compensation events and early warning seeds for the register.
Additional compensation events
NEC4 clause 60.1 lists standard events, but Contract Data allows you to add project-specific ones. Typical examples:
- Discovery of asbestos in defined areas.
- Changes in a named statutory authority’s requirements.
Each must be drafted clearly: “Can a reasonable person on site tell when this event has occurred?”
Initial items for the Early Warning Register
NEC4 renamed the NEC3 “Risk Register” to Early Warning Register to emphasise it is about managing risk, not re-allocating it.
In Part One, the Client can list known risks to be placed on this register at the start (e.g. “risk that third-party bridge owner delays approvals”). The Contractor can add its own in Part Two.
Remember: putting something in the Early Warning Register does not automatically change who bears the cost if it happens – that still comes from clauses 60 & 61. The EWR is about visibility and management, not risk transfer.
4.7 Z clauses: when and how to customise
When you genuinely need bespoke conditions, Z clauses are your tool – but they’re more like surgery than wallpaper. Each new Z clause cuts into a carefully balanced standard form.
Keep them short and focused
For example, “Z1 – BIM Protocol” referencing a separate agreed document, instead of rewriting core NEC mechanisms.
Use NEC-style plain English
Avoid old-school variation language like “Hereafter the Contractor shall be liable for all whatsoever”. Stick to NEC’s clear, verb-driven style.
Check interactions
Make sure your Z clause doesn’t quietly kill early warning, change the CE list in a clumsy way, or reduce the Contractor’s time to notify below the 8-week structure in clause 61.3 without thinking through the consequences.
Think of Z clauses as “last resort, not first instinct.” If an existing X/Y/W option achieves what you want, use that instead of inventing a bespoke risk shift.
5. Completing Contract Data Part Two (Contractor side)
Part Two is your offer, not admin — it tells the Client who you’ll deploy, how you’ll programme the work, how you’ll price it, and how you see the risk.
Part Two is where the Contractor turns Part One into a concrete offer — naming Key People, locking in a realistic programme, exposing the pricing logic and stating assumptions, so the NEC4 contract reflects reality rather than wishful thinking.
5 Completing Contract Data Part Two (Contractor side) – offer, not admin
Now flip the lens. Part Two is the Contractor’s “this is how we’re actually going to do it” statement. It’s where you convert the Client’s strategy in Part One into a live, deliverable offer.
5.1 Key People – the real leadership team
Here the Contractor names the people who will actually run the job day-to-day. Typically, you’ll see:
These names matter because the contract often treats Key People differently – replacing them can require Project Manager acceptance. So the Contractor should avoid naming people who are “nice to have” but not truly committed to the project.
You list your star Planner or Commercial Manager as a Key Person “to look good” but they are only partially available. Six months in, you need to move them to another job. Now you need formal acceptance to replace them, and the Client may ask hard questions about why your bid team oversold the resource plan.
5.2 Programme – giving Part One dates a reality check
Even if the full programme is a separate document, Part Two normally references it. This is where the Contractor shows whether the dates in Part One are actually buildable.
From the Contractor’s side – good practice
- Submit a realistic, logic-linked programme that actually hits the Completion Date and any Key Dates from Part One.
- Show time risk allowances and float as NEC expects, so that if a compensation event happens, you can demonstrate its impact.
From the Client side – simple questions to ask
When you review the Contractor’s Part Two:
- “Does this programme look like it can really deliver the dates we wrote in Part One, or have we pushed them too far?”
- “Do we clearly see critical path, float and time risk allowances, or is the programme just a bar chart with no logic?”
If the answer is “no, this doesn’t look deliverable”, fix it now – by reworking Part One dates or clarifying access and constraints – not in month 6 via a messy compensation event.
5.3 Pricing and fee data – especially under Options C–F
In Part Two, the Contractor fleshes out the money side. This is where the Client can see whether the commercial engine matches the Scope and the chosen main Option.
Activity Schedule or BoQ (depending on option)
- Every part of the Scope should be visible somewhere in the pricing.
- Any line at “zero” or left blank should be consciously agreed, not accidental.
Fee percentages (for Options C–F)
Direct Fee % and Subcontract Fee % are applied to Defined Cost to form the amount due. Small percentage differences can have big financial consequences over a large project.
Working Areas
For cost-based options, only costs incurred in defined Working Areas qualify as Defined Cost. If the Contractor forgets to list a site compound, design office, or off-site fabrication yard they rely on, they may struggle to recover those costs later.
You win an Option C target contract but leave key site compounds and off-site facilities out of the Working Areas list. Halfway through the job, you realise that a big slice of your actual Defined Cost is technically “off-contract”. You’re now arguing eligibility line-by-line instead of delivering the works.
5.4 Contractor’s assumptions and risk view
Smart Contractors also use their tender return and Part Two data to show how they see the project risk picture. Common moves include:
- Stating key assumptions – for example, “Assumed access to all areas 24/7” or “Assumed Client obtains permit X by date Y”.
- Suggesting items for the Early Warning Register.
From the Client’s side, the important thing is: don’t leave those assumptions floating in tender correspondence or email trails.
If the parties accept them, bring them into the contract – either as additional compensation events in Part One, text in the Scope, or explicit wording in Z clauses. That way, future compensation events are based on what both sides actually recorded, not on who has the better email archive.
6. Time bars, early warnings and Contract Data – how they interact
Clause 61.3 creates the famous 8-week time bar, but your Contract Data quietly controls the reply periods, CE plumbing and early warning habits that decide whether teams actually meet those deadlines.
Clause 61.3’s 8-week bar doesn’t live in Contract Data, but Contract Data decides all the reply periods, extra compensation events and early warning habits around it — if those numbers are lazy or unclear, even good teams lose entitlement by accident.
6 Time bars, early warnings and Contract Data – how they interact
One of the biggest “gotchas” people meet in NEC4 is clause 61.3:
For certain events, if the Contractor doesn’t notify within 8 weeks of becoming aware that the event has happened, they lose any entitlement to extra time and money (unless the Project Manager should have notified and failed to).
Where does Contract Data come in?
Contract Data doesn’t rewrite clause 61.3, but it does quietly control how easy (or impossible) it is to comply with it in practice:
- Periods for reply on compensation events, quotations, and programmes — if these are too short or unclear, the system jams and people miss deadlines.
- Additional compensation events — some clients try to shorten or tweak the time bar through Z clauses; this needs great care because it cuts across NEC’s logic and can be seen as unfair.
| Lever | Driven by | Lives mainly in |
|---|---|---|
| 8-week time bar (CE notice) | Clause 61.3 | Core ECC clauses |
| Reply times to CE notices / quotations | Contract Data choices | Contract Data Part One |
| Extra compensation events | Contract Data + Z clauses | Contract Data + Z section |
| Early warning behaviour | Clauses 15 & 16 + culture | Early Warning Register + team habits |
You keep the 8-week time bar, but set unrealistically short reply periods in Contract Data. Quotes sit unanswered, programmes aren’t accepted in time, and everyone is constantly out of step. Now the Contractor is technically time-barred and the Project Manager is technically late — a perfect recipe for dispute.
Meanwhile, the Early Warning Register (now correctly named in NEC4) is meant to be a proactive tool, not a sneaky way to shift risk. Both parties must give early warnings as soon as they see something that might hit time, cost or quality.
Contract Data can “seed” this Early Warning Register by listing known risks at the start. But it does not change who bears the cost if those risks occur — that still comes from clauses 60 & 61. The EWR is about visibility and management, not risk transfer.
A professional Contract Data set makes the early warning and CE system:
- Clear – everyone knows who to notify and how long they have.
- Usable – periods are realistic for the project’s scale and governance.
- Fair – no hidden traps in Z clauses that secretly shorten time bars.
7 Red-flag checklist 🚩
Before anyone hits “print and sign”, run through this, line by line:
-
Any blank lines in Contract Data Part One or Part Two?
If yes, ask: “Is there a known default? Do we really want it?” If not, fill it. -
Do Part One and Part Two agree on the basics?
Same Main Option, same Completion Date(s), same understanding of pricing structure, same list of X/Y/W options. -
Are all option-related numbers filled?
X7 damages rate, X16 retention %, X1 inflation index, X13 bond value, X18 caps, etc. -
Is each Z clause justified and NEC-compatible?
If a Z clause rewrites early warning, compensation event procedures, or time bars, you should have a very good reason and a legal opinion. -
Can a PM or QS answer these questions from the Contract Data alone?
- “When is the next payment assessment?”
- “How long do I have to reply to a CE quotation?”
- “How long does the Contractor have to correct this defect?”
7. One-page mini checklist you can print or turn into a widget ✅
Use this one-page checklist before signature to sanity-check both Contract Data Parts One and Two.
Tick through this mini checklist and you’re no longer just “filling in a form” – you’re genuinely completing the NEC4 Contract Data like a pro.
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Main Option (A–F) selected and stated in full.
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W Option and all X/Y Options listed and understood.
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Any required figures for options inserted (damages, retention, caps, etc.).
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Scope, Site Information, and pricing documents are clearly listed in Part One.
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No contradictions between Scope and Contract Data on dates, payments, or responsibilities.
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Starting Date, Access Date(s), Completion Date and Key Dates are all filled in and realistic.
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Period for reply and programme submission intervals stated and workable.
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Defects date and defect correction period(s) intentionally chosen and recorded.
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Payment cycle and final date for payment match law and policy.
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Insurance levels and any liability caps are stated (or consciously left unlimited).
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Any additional compensation events are clearly defined.
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Initial Early Warning / risk items listed in Part One and supplemented in Part Two.
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Key People listed and actually available.
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Programme reference aligns with Completion Date and Key Dates.
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Activity Schedule / BoQ fully priced and tied to the Scope.
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Fee % and Working Areas are complete and understood.
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Important tender assumptions brought into the contract (Scope / Contract Data / Z clauses).
Next steps: deepen your NEC4 drafting
Once your checklist is green, use these pieces to refine risk, IP and payment logic around your Contract Data: