JCT vs NEC: what actually changes for a contractor
Updated: 7 hours ago
By Roman Bazelchuk | NEC Accredited Project Manager | APMG Project Planning and Control
Founder, NEC Planning Solutions Ltd
Moving from JCT to NEC changes four things at once. The programme becomes a contractual instrument rather than a management tool, extensions of time become compensation events on an eight-week clock, change is valued from Defined Cost rather than your tendered rates, and early warnings become an obligation with financial consequences.
The comparisons written about these two contracts almost all stop at philosophy. JCT allocates risk, NEC encourages collaboration, and both statements are true and useless at eight o'clock on a Monday when the project manager has rejected your programme.
This is written for the other situation. A contractor whose commercial and planning teams have run JCT jobs for years has just won an NEC contract, and the habits that worked perfectly well on the last five projects are now quietly costing money. Nothing about that team is incompetent. They are running the wrong operating system.
What follows is what actually changes, in the order it will hit you, and what to do about each. If the specific question is how delay works, that is covered in depth in NEC delay analysis and extension of time, which sets out why NEC time entitlement runs forwards rather than backwards.
JCT vs NEC: where the difference actually bites
Both contracts have a programme, a mechanism for extending time and a way of valuing change. The words look equivalent on a contents page. The operating consequences are not.
Under JCT the contractual centre of gravity is the Completion Date and the events that adjust it. The programme supports that argument. Under NEC the contractual centre of gravity is the Accepted Programme itself, and almost every entitlement is measured against it. Once you see that, the rest of the differences stop being a list to memorise and become one shift with four consequences.
The programme stops being a management tool
Under the JCT Standard Building Contract the contractor provides a master programme under clause 2.9, and the Contract Particulars offer an option for critical paths to be shown. The programme is only required to be updated when applying for an extension of time. There is no sanction for producing a thin one. The JCT Design and Build form does not expressly require a construction programme at all.
Under NEC4 the programme is obligatory, it is submitted for acceptance under clause 31, it is revised at the interval stated in the Contract Data, and it carries prescribed content including float, time risk allowances and Key Dates. It is the document against which compensation events are assessed. A JCT team that treats it as a reporting obligation, produced monthly and filed, has misunderstood what it is for. The mechanics of getting one accepted are set out in the Clause 31 programme acceptance guide, and what to do when one comes back rejected is in the Clause 31.3 response playbook.
Extensions of time become compensation events, on a clock
Under JCT the contractor notifies a Relevant Event and the contract administrator decides on a fair and reasonable extension. Time and money run on separate tracks, because loss and expense is claimed separately under the Relevant Matters list. Notices matter, but on the traditional forms lateness has usually gone to weight rather than to entitlement.
NEC merges the two. A compensation event changes the Prices and the Completion Date in one assessment, and clause 61.3 puts an eight-week limit on notification measured from when the contractor became aware. Miss it and the entitlement does not survive, however good the underlying case. The courts have read awareness objectively, so an argument that nobody senior saw the instruction is not the defence it feels like.
There is a related point on the JCT side worth knowing, because it cuts differently from the folklore. The extension of time notice under JCT is not a condition precedent, and the 2024 Design and Build edition did not make it one: what it added was a timetable, a fourteen day window for the employer to request further particulars and an eight week limit on its decision, down from twelve. The money notice is another matter. In FES Ltd v HFD Construction Group Ltd the court held that the loss and expense notice provisions do operate as a condition precedent, so a contractor that misses them keeps its extension and loses the money that should have come with it.
The practical consequence for a JCT team is a change of reflex. The instinct to build the case first and notify when it is watertight is exactly wrong under NEC. Notify early, then build. The time bar and the CE clock covers how the whole sequence runs. The two mechanisms compared side by side, and where JCT-trained teams misread them, is in Relevant Events vs compensation events.
Change stops being valued at your rates
This is the difference that costs the most money and gets noticed the latest, usually when the first substantial change is settled and the number is not what anyone expected.
Under JCT a variation is valued using the Valuation Rules, and the rates in the contract documents do most of the work. Pricing change from your own tendered rates is the normal position, and the commercial team's instincts are built around it.
Under NEC the change to the Prices is assessed from Defined Cost plus the Fee under clause 63.1. Your tendered rates apply only if the project manager and contractor agree to use them under clause 63.2. Absent that agreement the activity schedule rate is simply not the answer, and the assessment is built from cost components and substantiated. On Options A and B this catches teams out badly, because nothing forces cost records to exist until a compensation event arrives, by which time the detail to justify people, plant and subcontract cost may never have been captured. How the money limb is built is set out in the NEC compensation event quotation guide.
Early warnings become an obligation with a price
JCT has nothing that works like clause 15. There are notice provisions, but no standing duty to flag matters that might affect cost, time or quality before they crystallise, and no financial consequence for staying quiet.
Under NEC the early warning is a contractual obligation on both parties, maintained in a register and reviewed at early warning meetings. It also has teeth: where a contractor fails to give an early warning that an experienced contractor would have given, the compensation event can be assessed as if it had been given. In plain terms, silence can reduce what the event pays. A JCT team that treats early warnings as courtesy correspondence, or worse as an admission against interest, is choosing to be paid less.
What this looks like in the first month
The failures are predictable, which is the good news, because predictable failures are preventable ones.
The programme is late and thin
Submitted when convenient rather than within the period in the Contract Data, missing float, time risk allowances and Key Dates, and never formally accepted. Every entitlement that follows is then measured against a baseline nobody agreed.
Events are logged, not notified
The site team records issues in minutes and photographs and waits to build the case. Eight weeks passes on the earliest ones. The record is excellent and the entitlement is gone.
Cost records do not exist
On a priced option nothing forces Defined Cost records until a change arrives. When it does, the quotation is built on estimates that cannot be substantiated, and the project manager strips what cannot be shown.
Early warnings are avoided
Treated as weakness or as an admission, when the contract treats them as a duty and prices the failure to give them.
Summary
The differences between JCT and NEC are not a matter of tone. Under JCT the programme supports an argument about the Completion Date, change is valued from the contract rates, and time and money are claimed on separate tracks. Under NEC the Accepted Programme is the instrument almost every entitlement is measured against, change is assessed from Defined Cost and the Fee, time and money are settled together, and notification runs on an eight-week limit that ends valid claims.
A JCT team is not short of competence when it moves to NEC. It is running habits calibrated to a different contract. The programme has to be built to be accepted rather than to be filed, events have to be notified before the case is complete rather than after, cost records have to exist before they are needed, and early warnings have to be given rather than avoided. Get those four right in the first month and the contract works as intended.
How NEC Planning Solutions helps
NEC Planning Solutions Ltd is a UK-registered project controls consultancy, director-led and QA-governed, with senior NEC-accredited review on every output. A large part of the work is exactly this transition: setting up the programme, the registers and the cost records correctly for teams whose experience is JCT, then keeping the Accepted Programme current so entitlement holds. See Clause 31 and 32 programme compliance, compensation event and change support, and the same discipline applied on a live carbon capture project.
Download the First 30 Days checklist
The first month on an NEC job for a team coming from JCT, in two pages: reading the Contract Data, getting a first programme accepted, opening the early warning register, starting the compensation event clock, and setting up cost records for Defined Cost. Free, direct download, no sign-up.
Frequently asked questions
What is the main difference between JCT and NEC contracts?
JCT allocates risk through a traditional structure where the programme supports an extension of time argument and change is valued from contract rates. NEC manages risk actively: the Accepted Programme is the instrument entitlement is measured against, change is assessed from Defined Cost plus the Fee, and time and money are settled together as compensation events.
Is the programme a contract document under JCT?
Not in the way it is under NEC. The JCT Standard Building Contract requires a master programme under clause 2.9, with critical paths optional in the Contract Particulars, and it need only be updated when applying for an extension of time. The Design and Build form does not expressly require one at all.
Do my tendered rates apply to changes under NEC?
Only if the project manager and the contractor agree to use them under clause 63.2. Otherwise the change to the Prices is assessed from Defined Cost plus the Fee under clause 63.1, built from cost components and substantiated. This is the opposite of the JCT Valuation Rules position most commercial teams are used to.
How long do I have to notify a compensation event?
Eight weeks from becoming aware that the event has happened, under clause 61.3. Miss it and the Prices, the Completion Date and any Key Dates are not changed. Awareness is judged objectively, so arguing that nobody senior read the instruction is not a reliable defence.
Do early warnings affect what a compensation event pays?
Yes. Where the contractor fails to give an early warning that an experienced contractor would have given, the event can be assessed as if the warning had been given. JCT has no equivalent mechanism, which is why teams moving across often treat early warnings as optional correspondence and lose money doing so.
About the author
Roman Bazelchuk is the Founder of NEC Planning Solutions Ltd, a UK project planning and controls consultancy supporting contractors with NEC programme compliance, compensation event assessments and live project controls. He is an NEC Accredited Project Manager and holds the APMG Project Planning and Control qualification, with a BEng in Mechanical Engineering and postgraduate training in Planning and Control.
NEC Planning Solutions provides contract-aware planning support through a QA-governed delivery model, helping project teams keep programmes accepted, current and commercially useful from tender through to live delivery.
First NEC job after years of JCT?
If a team used to JCT is starting an NEC contract, NEC Planning Solutions will set the programme, the registers and the cost records up correctly before the habits set, and review the first submissions before they go in.
