Defined Cost in NEC4: what it includes, what is disallowed and how it is recovered
Updated: Oct 19
By Roman Bazelchuk | NEC Accredited Project Manager | APMG Project Planning and Control
Founder, NEC Planning Solutions Ltd
Defined Cost in NEC4 is the contract's measure of what the work cost the Contractor: the cost of the components in the Schedule of Cost Components less Disallowed Cost on Options C, D and E, or in the Short Schedule on Options A and B. Compensation events are assessed on it, with the Fee added.
On Options C to F, Defined Cost is also how the Contractor is paid, at each assessment date, through the Price for Work Done to Date. That double role is where recovery goes wrong. It breaks down when the Accepted Programme and the cost record stop describing the same job. The spend can be genuine and still count against the Contractor, who can prove the money went out but not that the compensation event caused it.
Expensive failures on an NEC Option C or D project rarely start with a disputed quotation. They start earlier, when different parts of the Contractor's own business stop describing the same job. The planner is modelling one version of reality. The QS is pricing another. Site is living a third. Finance is capturing a fourth. Once that fracture opens, the Contractor starts losing what NEC rewards in change valuation: coherence.
That, in my view, is the real hidden problem behind a great deal of weak NEC Defined Cost recovery. The issue is not simply that records are missing. It is that the Contractor no longer has a single believable story about what changed, when it changed, what it did to the remaining works, and why the resulting spend should sit with the Client rather than the Contractor.
This guide sets out what Defined Cost includes under each main Option, what Disallowed Cost takes out and how the cost is recovered, with a worked example. It then follows the four places where recovery breaks down on Options C and D.
What Defined Cost in NEC4 includes
Defined Cost is the contract's measure of what the work cost the Contractor. It is built from the components listed in a schedule, valued the way that schedule says, rather than from every invoice the business paid. Under each main Option, compensation events are assessed on it, with the Fee added, unless the Project Manager and the Contractor agree to use rates or lump sums instead (clause 63.2).
Aspect | Options A and B | Options C, D and E |
Defined Cost | Clause 11.2(23): the cost of the components in the Short Schedule of Cost Components | Clause 11.2(24): the cost of the components in the Schedule of Cost Components, less Disallowed Cost |
Disallowed Cost | Not part of these Options | Deducted, as defined in clause 11.2(26) |
Interim payment | Not based on Defined Cost: the Prices for completed activities on the Activity Schedule (A), or completed quantities at the Bill of Quantities rates plus a proportion of each lump sum (B) | The Price for Work Done to Date, clause 11.2(31): forecast Defined Cost plus the Fee |
Compensation events | Defined Cost from the Short Schedule, plus the Fee | Defined Cost from the Schedule of Cost Components, plus the Fee |
Table 1: Defined Cost under the NEC4 ECC main Options
Option F, the management contract, defines it differently, in clause 11.2(25): the payments due to Subcontractors for the work subcontracted, without counting any amount twice, and the prices for work done by the Contractor, less Disallowed Cost.
The Schedule of Cost Components sorts the cost into eight components: people, Equipment, Plant and Materials, Subcontractors, charges, manufacture and fabrication, design, and insurance. NEC4 made payments to Subcontractors one of them, where NEC3 counted them outside the Schedule, in the definition itself. The Short Schedule used on Options A and B is lighter, and prices some components at rates rather than at recorded cost: people at the People Rates for the time spent on the work, and listed Equipment at the rates in a published list, adjusted by the percentage tendered in the Contract Data.
Whatever Defined Cost leaves out is covered by the Fee. Clause 52.1 treats the Contractor's costs that are not included in Defined Cost as included in the Fee, so head office overheads and profit come back through the fee percentage, not as cost. NEC4 has one fee percentage, where NEC3 had a direct fee percentage and a subcontracted fee percentage.
Disallowed Cost: what NEC4 takes out
Disallowed Cost is cost the Contractor has incurred but the contract will not pay. It applies to Options C, D and E under clause 11.2(26), and Option F has its own, shorter definition in clause 11.2(27). NEC3 opened the definition with the words "cost which the Project Manager decides", which governed its first group of headings. NEC4 dropped those words, so the test is whether a cost falls under one of the listed headings. Table 2 sets them out, in paraphrase.
Disallowed Cost, in paraphrase | Where it tends to bite on a live job |
Cost not justified by the Contractor's accounts and records | Spend the records cannot tie to work on the programme |
Cost that should not have been paid to a Subcontractor or supplier under its contract | Payments beyond what the subcontract required |
Cost incurred only because the Contractor did not follow an acceptance or procurement procedure stated in the Scope | A package let, or a design used, before the step the Scope requires |
Cost incurred only because the Contractor did not give an early warning the contract required | Cost a warning on time would have avoided |
Cost incurred only because the Contractor did not notify the Project Manager of adjudication or tribunal proceedings with a Subcontractor or supplier | A subcontract dispute the Project Manager learns about too late |
Correcting Defects after Completion, or Defects caused by not complying with a constraint in the Scope on how the Contractor Provides the Works | Rework the contract places with the Contractor |
Plant and Materials not used to Provide the Works, after allowing for reasonable wastage, unless resulting from a change to the Scope | Over-ordering and waste beyond a normal allowance |
Resources not used to Provide the Works, after allowing for reasonable availability and utilisation, or not taken away from the Working Areas when the Project Manager asked | Equipment or people kept on site with no programme reason |
Preparing for and conducting an adjudication, payments to a member of the Dispute Avoidance Board, or tribunal proceedings between the Parties | The cost of a dispute with the Client stays with the Contractor |
Table 2: Disallowed Cost under NEC4 Options C, D and E
In my view three of these headings do most of the damage on a live job, and each runs through the programme. The first is records: a cost the records cannot tie to work on the programme is the easiest to disallow and the hardest to win back. The second is early warnings: cost incurred only because a required warning was not given stays with the Contractor, so the early warning register is a cost document as much as a risk one. The third is idle resources: Equipment kept on site needs a reason on the programme, or it reads as resources not used. A disallowed cost is not paid, and it earns no Fee.
How Defined Cost is recovered
Defined Cost comes back to the Contractor by two routes: through payment on Options C to F, and through compensation events.
Through payment, on Options C to F
On Options C, D and E the amount due at each assessment date is built on the Price for Work Done to Date: the total Defined Cost the Project Manager forecasts the Contractor will have paid before the next assessment date, plus the Fee (clause 11.2(31)). Option F pays the same way on its own definition. The Contractor keeps the accounts and records the contract lists (clause 52.2, or 52.3 on Option F), and the Project Manager can inspect them at any time within working hours (clause 52.4).
Clause 50.9, new in NEC4, lets the Contractor close the account in stages. It notifies the Project Manager when the Defined Cost for a part of the works has been finalised and makes available for inspection the records that show it has been correctly assessed. Within thirteen weeks the Project Manager accepts it as correct, asks for further records or notifies errors in the assessment. The Contractor then has four weeks to provide the records or correct the errors, and the Project Manager a further four weeks to accept it or to notify the correct assessment. If the Project Manager does not notify a decision in time, the Contractor's assessment is treated as correct. The NEC3 to NEC4 guide sets it alongside the other changes NEC4 made.
On Options C and D the target sits above all of this. Payment follows Defined Cost, and the difference between the total of the Prices and the final Price for Work Done to Date is shared under clause 54, assessed in a preliminary way at Completion of the whole of the works and finally in the final amount due, not month by month. Option A vs Option C works through the share.
Through compensation events
A compensation event changes the Prices by its effect on the actual Defined Cost of the work done by the dividing date, the forecast Defined Cost of the work not yet done, and the resulting Fee (clause 63.1). Where the event arises from the Project Manager or the Supervisor giving an instruction or notification, issuing a certificate or changing an earlier decision, the dividing date is the date of that communication. For any other event it is the date the event was notified. What the dividing date decides is covered in its own guide.
On Options A and B the assessment uses the Short Schedule, so the change to the Prices comes from cost components, not from the tendered rates, unless the Project Manager and the Contractor agree to use rates or lump sums. On Options C and D the change to the Prices moves the target, not the interim payment. Once a compensation event has been implemented, its assessment is not revised except as the conditions of contract state (clause 66.3), and a forecast that later proves wrong does not of itself reopen it. That is why the quotation needs the programme behind it.
A worked example: one compensation event on Option C
The figures are illustrative. A Contractor on an Option C contract, with a fee percentage of 12 per cent, meets physical conditions in week 12, gives an early warning the same week, and notifies them as a compensation event in week 15. The event did not arise from anything the Project Manager or the Supervisor did, so the dividing date is the date of notification, week 15. By then three weeks of the extra work are done.
Component | Work done by the dividing date, actual | Work not yet done, forecast |
People | £18,400 | £31,000 |
Equipment | £9,600 | £14,000 |
Subcontractors | £0 | £22,000 |
Defined Cost | £28,000 | £67,000 |
Table 3: one illustrative compensation event on Option C, split at a dividing date in week 15
The Defined Cost of the event is £95,000. The Fee at 12 per cent adds £11,400, so the Prices, and with them the target, rise by £106,400. The actual column comes from timesheets, hire records and the cost ledger. The forecast column comes from the programme: the activities the event adds or extends, their durations and the resources on them, read from a revision that shows the event's effect.
One line shows how real cost drops out. The hire records show £12,000 of Equipment for the three weeks, but one excavator stayed on site for a week after the Project Manager asked for it to be taken away. That £2,400 is Disallowed Cost: a resource not taken away from the Working Areas when the Project Manager asked. It is not in the assessment, it is not paid, and it earns no Fee, so the actual Equipment cost in the event is £9,600.
Had the Contractor notified in week 12, the whole of the event's cost would have been forecast and argued from the programme. Notified in week 15, £28,000 of it has to be proved from records instead.
COMMERCIAL CONSEQUENCE On Option C a compensation event assessed too low does not cut the next payment. The Contractor is still paid Defined Cost plus the Fee. The target rises by less than it should, and the Contractor carries its share of the shortfall at Completion and in the final amount due. The loss arrives late and is easy to miss. |
Pillar One: Where the programme stops explaining the spend
The Accepted Programme is not a cost report. It is not meant to be. But on a live NEC job it becomes one of the main documents that makes the cost record commercially intelligible.
That point is often missed because planning and commercial teams tend to look at the same event through different lenses. The planner sees sequence, access, productivity, dependency and finish dates. The QS sees labour, plant, subcontract accounts, invoices and accruals. Both may be looking at the same underlying disruption, but unless those two records still connect, the Contractor's position begins to weaken long before anyone says the words Disallowed Cost.
This is the real meaning of the QS-planner bridge. It is not about office harmony or better collaboration for its own sake. It is about preserving the commercial link between what the programme says changed and what the Schedule of Cost Components says it cost.
If labour extends because access slipped, the programme needs to remain good enough to show how that slip altered the sequence and why the labour remained productive or unavoidably present. If plant stays on site longer, the programme needs to show the event that kept it there. If a subcontract account rises because resequencing or disruption pushed the package into a different working pattern, the Accepted Programme needs to carry enough logic to make that intelligible.
Otherwise the Contractor ends up in the weakest possible position. It can prove that money was spent, but not that the contract should treat that spend as the consequence of the event being valued.
This is where many NEC target cost jobs quietly become vulnerable. The records still exist. The Contractor may even feel well documented. But the time record and the money record are no longer speaking the same language. Once that happens, cost starts to look like accumulation rather than consequence. And accumulation is harder to defend than consequence.
The uncomfortable truth is that many contractors still treat the programme as if it were mainly a planning document, when under NEC it is often doing a second job at the same time. It is helping explain why cost moved.
Pillar Two: Where bargaining power starts to move
The dividing date is one of the clearest examples of NEC4 being commercially sharper than many teams realise. It does not merely organise valuation. It determines the line between what is treated as actual Defined Cost and what is still assessed as forecast Defined Cost.
That distinction matters because it is also the line between two very different commercial environments.
On one side sits forecast. Forecast is not easy, but it is still a prospective exercise. It allows the Contractor to explain how the remaining works would have unfolded, how the event altered that sequence, and why the expected future spend should be assessed in the way proposed. The Contractor still has room to present logic, causation and commercial judgment.
On the other side sits actual. Once the exercise tips into actuals, the atmosphere changes. The valuation becomes more forensic. The Project Manager, or anyone later scrutinising the account, starts looking harder at invoices, timesheets, plant records, labour patterns and procurement trails. The argument becomes less about what the programme says will happen and more about what the Contractor can now prove already happened.
That is why the Accepted Programme matters so much more than many site teams think. A current and credible programme keeps the Contractor arguing from prospective logic. A stale or rejected programme pushes the Contractor towards reconstruction. The cost record may still exist, but it is no longer anchored to a believable forecast of the remaining works.
That is the point at which bargaining power starts to move.
Many contractors misread this moment. They think they still have a valuation issue that can be improved by working harder on the quotation. In reality, the deeper problem began earlier. The live record stopped keeping pace with the job. Once that happens, the Contractor is no longer advancing a coherent prospective case. It is trying to rebuild one from fragments.
This is also why it is dangerous to confuse the clause 20.4 forecast of total Defined Cost with the contractual machinery used to assess a compensation event. The former shows how the overall financial position is moving. The latter is about the valuation of a specific change. A contractor can have a perfectly respectable overall target cost forecast and still be badly exposed on a particular compensation event because the Accepted Programme, the notice position and the cost build-up have drifted apart. That distinction is small in theory and expensive in practice.
That is also where the Accepted Programme starts losing its protective value, which when an Accepted Programme stops protecting a specialist contractor explores from the specialist contractor's side.
Pillar Three: Why real cost still becomes vulnerable
Disallowed Cost is often spoken about as though it were a dramatic sanction that appears only in extreme cases. That is too simple. On real projects, it often arrives more quietly.
It arrives when the cost record is real, but the explanation behind it has weakened.
A plant invoice may be entirely genuine. The equipment may well have been on site. But if the programme no longer shows the event, sequence change or access problem that kept it there, the commercial footing under that spend becomes softer.
The same is true of labour. The hours may be genuine. The people may have been needed. But if the programme and notice trail do not still explain why that extra labour sat where it did in the sequence, the Contractor is left proving spend without proving contractual consequence.
That is the point at which Defined Cost recovery begins to break down.
A more useful way to understand Disallowed Cost on NEC Options C and D is not as a punishment for one dramatic mistake. It is as the audit consequence of weak linkage. Once time logic and cost logic drift into separate stories, real cost starts becoming commercially vulnerable.
This is why I think the industry often discusses NEC cost recovery too narrowly. It is still usually framed as a QS issue, as though the commercial team's task is simply to gather the right invoices, timesheets and back-up. That matters, of course. But many failures happen before the QS ever sits down to build the case. They happen when the sequencing logic has already thinned out, when the programme has stopped evolving with the job, and when the explanation for the spend has become more intuitive than demonstrable.
In that sense, Disallowed Cost is often not the start of the commercial failure. It is the point at which an earlier internal fracture becomes visible.
On an Option C or D job, NEC Planning Solutions updates the programme every month, with a variance narrative that explains what moved and why, so the programme put forward for acceptance still explains the Defined Cost recorded under it, as part of its live project controls and reporting service.
Monthly support starts from £1,400 plus VAT.
Pillar Four: The price of hindsight in NEC Defined Cost
Northern Ireland Housing Executive v Healthy Buildings (Ireland) Ltd [2017] NIQB 43 remains worth mentioning, but only carefully. It should not be treated as a catch-all authority for every NEC valuation dispute. It was a Northern Ireland High Court decision on an NEC3 Professional Services Contract, not an NEC4 ECC target cost works contract, and commentators differ on how far it carries into NEC4. Still, it remains instructive because it shows what can happen once the contractual machinery drifts too far behind the work itself.
The core warning is not legalistic. It is commercial.
Once a project's change process has fallen badly out of step with the live job, hindsight starts gaining ground. In Healthy Buildings the quotation came after the work was done, not as a genuine forecast, and the court held on preliminary issues that it should be informed by the best information available on the actual cost and time. It ordered the consultant to disclose its records of both. That is the real lesson contractors should take from it.
The value of the case is not that it gives a slogan to quote in argument. The value is that it reminds contractors what happens when they lose the protection of a live, believable forecast. Once that happens, the room for forward-looking commercial logic narrows, and the room for retrospective scrutiny expands.
That is rarely a comfortable environment for the party whose programme and cost record have already stopped agreeing.
This is why NEC should not be treated as a contract that merely rewards compliance. It rewards timeliness of thought. It rewards parties who can keep the operational record and the commercial record sufficiently close to each other that the valuation of change remains a prospective exercise, not a post-mortem.
The author's view
On NEC Options C and D, profit is not protected only by building efficiently. In my view it is protected by keeping time and money in one believable story.
If the current Accepted Programme no longer explains the spend landing in the Schedule of Cost Components, the issue is rarely the quotation alone. The quotation is simply where the fracture becomes painful.
The real problem began earlier, when the Contractor allowed its own internal records to separate into different realities. One version of the job sat in the programme. Another sat in the cost ledger. A third sat in people's heads. By the time those versions needed to be reconciled under section 6 of the contract, the Contractor was already on the back foot.
That is why Defined Cost recovery breaks down. Not because the Contractor failed to spend the money. Not because the event was necessarily weak. It breaks down because the programme stopped forecasting the same reality that the cost record later tried to prove. By the time that becomes obvious, the margin has often already gone.
Defined Cost in NEC4: frequently asked questions
What is Defined Cost in NEC4?
Defined Cost is NEC4's measure of what the work cost the Contractor. On Options A and B it is the cost of the components in the Short Schedule of Cost Components. On Options C, D and E it is the cost of the components in the full Schedule, less Disallowed Cost, and Option F has its own definition. Compensation events are assessed on it, with the Fee added.
What is the difference between Defined Cost and the Fee?
Defined Cost is the cost the schedule recognises. The Fee is the fee percentage applied to it, and it covers what Defined Cost leaves out: clause 52.1 treats the Contractor's other costs, such as head office overheads, as included in the Fee, which also carries profit. NEC4 has one fee percentage, where NEC3 had separate percentages for direct and subcontracted work.
What is Disallowed Cost under NEC4?
Disallowed Cost is cost the Contractor incurred but the contract will not pay, and it earns no Fee. On Options C, D and E it includes cost the accounts and records do not justify, cost incurred only because a required early warning was not given, and resources not used, after allowing for reasonable availability and utilisation, or not taken away when the Project Manager asked. Option F's list is shorter.
How does the dividing date split Defined Cost in a compensation event?
Under clause 63.1 the change to the Prices is the effect on the actual Defined Cost of the work done by the dividing date, the forecast Defined Cost of the work not yet done, and the resulting Fee. Forecast is argued from the programme. Actuals are proved from records, so where the dividing date is the date of notification, a late notice moves more of the event into proof.
Why does Defined Cost recovery break down on NEC Options C and D?
It usually breaks down before any quotation is disputed, when the Contractor's own records stop describing the same job. The planner models one version, the QS prices another and site lives a third. Once the programme no longer explains why cost moved, spend starts to look like accumulation rather than consequence, and genuine cost becomes hard to recover.
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.
Arrange a consultation
Accepted Programme on your Option C or D job no longer explaining the Defined Cost building up under it? We will find where the programme and the cost record parted, and how to bring them back together. The first consultation is 30 minutes with Roman Bazelchuk, Director, confidential, with no documents needed in advance. Email info@necplanningsolutions.co.uk or call 0330 223 7709. Our specialist contractor planning support is set out here.
