How to Price a Variation Order: JCT and NEC Methods Explained

Learning how to price a variation order is one of the first things any quantity surveyor has to get right, because getting it wrong costs someone real money - either the Employer through overpayment, or the Contractor through undervaluation. The catch is that the correct method depends entirely on which standard form governs the project. JCT and NEC do not just use different clause numbers for the same idea; they start from opposite philosophies about when and how a variation should be priced.

Under a JCT contract, a variation is valued largely after the event, measured against a hierarchy of contract rates, fair allowances and, where nothing else fits, daywork. Under an NEC4 contract, the same instructed change becomes a compensation event, priced before the work happens through a Contractor's quotation built on forecast Defined Cost plus Fee. Two QSs on two projects, handed the same instruction, would follow entirely different procedures to arrive at a number - and different timescales for doing so.

This article puts the two methods side by side rather than teaching either one from scratch. If you need the full JCT valuation mechanics, our companion guide on how to price variations in JCT contracts covers clause 5.6 and 5.7 in depth; if you want the wider variation lifecycle across all forms, see our complete QS guide to variation orders. Here, the focus is comparative: the philosophy behind each approach, how each is actually applied, a worked example run through both methods, and the mistakes that catch out QSs moving between the two.

By the end you will be able to look at a contract, identify which pricing regime applies, and know exactly what evidence, timescale and negotiating posture that regime demands - whether you are valuing a straightforward rate-based variation or assessing a full compensation event quotation.

Two Different Philosophies: Why JCT and NEC Value Change Differently

The gap between the two methods isn't a drafting quirk - it reflects two different theories of how contracts should manage change. JCT treats a variation as a discrete measurement problem. The Architect or Contract Administrator instructs a change, the work is carried out, and the QS values it afterwards by reference to what is already in the contract bills or Schedule of Rates. Time and money are handled as separate strands: an extension of time under clause 2.29 and loss and expense under clause 4.23 run alongside the valuation, not as part of it. This keeps each strand procedurally simple but means three connected consequences of one instruction can end up argued through three different routes.

NEC4 rejects that separation deliberately. A compensation event bundles the cost effect, the time effect and the effect on any Key Date into a single assessment, agreed - in principle - before the work happens. The Contractor forecasts what the change will cost using Defined Cost plus Fee, and that forecast becomes the new Prices once accepted. Nothing is left to be reconstructed from site diaries months later. This is why NEC is often described as a management contract as much as a pricing contract: the quotation mechanism forces early conversations about cost and programme that JCT's retrospective valuation does not require.

• JCT: valuation happens after the work, using rates fixed at tender stage as the anchor point.
• NEC4: valuation happens before the work, using a forecast of what the work will actually cost to deliver.
• JCT: time and cost are assessed through separate mechanisms (EOT, loss and expense, valuation).
• NEC4: time and cost are assessed together in one compensation event quotation.

The JCT Approach: Valuation Rules in Brief

The clause 5.6/5.7 hierarchy

JCT's Standard Building Contract sets out its valuation rules at clause 5.6 (measurable work) and 5.7 (daywork), with the JCT Design and Build using the equivalent 5.4/5.5 numbering. The hierarchy runs in a fixed order. Where the varied work is of similar character to work already priced in the contract bills and is carried out under similar conditions, the original rates apply without adjustment. Where the work is similar in character but conditions have materially changed, or the quantity varies significantly from what was billed, the same rates are used but with a fair allowance added or deducted to reflect the difference. Where the work is not of a similar character at all, it is valued at fair rates and prices - effectively a new rate built up from first principles. Only where the work genuinely cannot be properly valued by measurement does it fall to daywork, priced on labour hours, plant time and materials plus a percentage addition, and reserved for short-duration, limited-scope items rather than substantial variations.

Why this is retrospective by design

Because the anchor point is the contract bill rates set at tender, the QS's job is essentially forensic: identify what was billed, decide which tier of the hierarchy applies, and measure what was actually done. Most JCT projects also fold this valuation into the ongoing interim valuation cycle rather than settling it as a standalone event, meaning a variation's final value is often not fully agreed until the final account. Some JCT contracts include the optional Schedule 2 Quotation procedure, which lets the Contractor submit an advance quotation for a variation before carrying it out - a deliberate borrowing of NEC-style forward pricing - but this remains the exception rather than the default route. For the full valuation mechanics, clause references and worked calculations, see our dedicated guide, how to price variations in JCT contracts.

The NEC Approach: Quotations, Defined Cost and Fee

Compensation events, not variations

NEC4 does not use the word variation at all in its core mechanism - it uses compensation event, a broader category covering instructed changes to the Scope alongside a list of other qualifying events at clause 60.1, from late access to unforeseen physical conditions. Once an event is notified (subject to the Contractor's 8-week time bar under clause 61.3), the Project Manager instructs the Contractor to submit a quotation, unless the effect is assessed by the Project Manager directly.

Defined Cost plus Fee

The quotation is built on Defined Cost - a defined term, not simply actual spend - calculated using the Shorter Schedule of Cost Components for priced Options A and B, or the fuller Schedule of Cost Components for the cost-reimbursable Options C, D and E. Defined Cost captures people, Equipment, Plant and Materials and subcontracted work, priced at the components set out in the contract, and excludes anything the contract treats as Disallowed Cost. A Fee percentage, fixed in the Contract Data, is then added on top to cover overheads and profit. Clause 63.1 introduces the dividing date: costs for work already done by that date are assessed on actual Defined Cost, while costs for work not yet done are forecast. The parties can also agree to price a compensation event using rates or a lump sum instead, giving NEC4 more flexibility than its NEC3 predecessor.

Strict timescales, both ways

The Contractor generally submits its quotation within one week of being instructed to do so, and the Project Manager must reply within two weeks - accepting it, giving reasons for non-acceptance, or in some circumstances instructing a resubmission. If the Project Manager misses that reply window and does not extend it, the Contractor's quotation can be treated as accepted by default, which is a powerful incentive for the Project Manager side to stay on top of the compensation event log.

Side-by-Side: Pricing the Same Change Under Both Methods

The table below sets the two methods against each other across the questions a QS actually has to answer when a variation lands: who prices it, what it's priced against, when it's priced, and what happens if the parties disagree.

Worked Example: One Instruction, Two Pricing Routes

Take a simple scenario: the design team instructs an extra 200m3 of excavation and disposal because unforeseen ground conditions require a deeper foundation than originally detailed. Assume the same physical works, priced under each contract in turn.

Under JCT

The QS first checks whether excavation and disposal of this type and depth is already priced in the contract bills. If the existing rate was built for similar ground conditions and a similar depth, that rate is applied directly to the additional 200m3, and the valuation is largely a measurement exercise. If the deeper excavation requires different plant, longer haul routes for disposal, or additional temporary works, the QS applies the existing rate with a fair allowance to reflect those changed conditions. If the ground conditions are different enough that no existing rate reasonably applies - rock rather than the clay originally billed, for example - the QS builds a fair rate from first principles: labour, plant and material costs plus overheads and profit. Either way, this valuation is usually finalised once the additional work is measured on site, and formally captured in the next interim valuation or the final account.

Under NEC4

The same instruction is a compensation event. Before the extra excavation starts, the Contractor prepares a quotation forecasting the Defined Cost of the additional work - people, Equipment and Plant, and any subcontracted excavation and disposal - using the rates and definitions in the Shorter Schedule of Cost Components, then adds the Fee percentage from the Contract Data. The quotation also states any effect on the Completion Date if the extra excavation is on the critical path. The Project Manager has two weeks to accept it, request changes, or assess it independently. Once accepted, the Prices and, if relevant, the Completion Date are changed immediately - before a single extra cubic metre is dug.

Choosing the Right Approach: What Actually Governs Your Pricing

In practice, a QS doesn't choose between the two methods - the contract chooses for them. The first job on any variation is confirming which form and which edition is in play, because bespoke amendments frequently alter the standard valuation or compensation event clauses, and Contract Data or Z clauses can add, remove or reweight provisions. On a JCT project, that means checking whether the optional Schedule 2 Quotation procedure has been adopted, since it changes a retrospective valuation into something closer to an advance quotation. On an NEC4 project, it means confirming which main Option (A to E) applies, because that determines whether Defined Cost is assessed against the Shorter Schedule of Cost Components or the full Schedule of Cost Components - a meaningful difference in what can and cannot be claimed.

This matters commercially, not just procedurally. A QS who assumes JCT-style retrospective valuation on an NEC4 project will find compensation events piling up unpriced and unquoted, with the Contractor's cash flow suffering and the Project Manager exposed to deemed acceptance of quotations nobody has scrutinised. A QS who assumes NEC4-style advance quotation on a standard JCT project will waste time trying to negotiate a figure the Architect or Contract Administrator is actually entitled to determine unilaterally under the valuation rules, absent an adopted Schedule 2 Quotation procedure. Five minutes spent confirming the applicable clauses at the start of a variation saves considerably more time arguing about the wrong process later.

• Read the actual clauses in your contract, not the standard form from memory - amendments are common on both JCT and NEC.
• On JCT, decide early which tier of the 5.6 hierarchy applies; it shapes what evidence you need to gather.
• On NEC4, build the compensation event log as soon as an instruction or clause 60.1 event arises - the timescales start immediately, not once you feel ready.
• On mixed portfolios, keep a one-page cheat sheet per form so the pricing method is never assumed from habit.

Common Mistakes When Pricing Variations Under Either Method

Most pricing disputes on both forms trace back to a handful of recurring errors, and they tend to run in opposite directions depending on which contract a QS is used to.

• Applying JCT habits to NEC4 - waiting until the work is finished to price it, instead of quoting the compensation event in advance as clauses 61-62 require.
• Applying NEC4 habits to JCT - treating the QS's valuation as negotiable in the way an NEC quotation is, rather than as a determination based on the clause 5.6 hierarchy.
• Missing the JCT similar-conditions test - defaulting to fair rates and prices when the existing bill rate, adjusted with a fair allowance, was actually the correct starting point.
• Confusing Defined Cost with actual cost under NEC4 - claiming costs that fall outside the Schedule of Cost Components definitions, or failing to exclude Disallowed Cost.
• Missing NEC4's reply timescales - letting the two-week Project Manager response window lapse without extending it, risking deemed acceptance of a quotation that hasn't been checked.
• Ignoring optional hybrid mechanisms - not recognising that a JCT Schedule 2 Quotation, once adopted, effectively imports NEC-style advance pricing into a JCT project.

The underlying lesson is the same in both directions: pricing method is a feature of the contract, not a personal preference or a habit carried over from the last project. Before pricing a single variation, confirm the form, the edition, any amendments, and - on NEC4 - the main Option in use. That five-minute check is what separates a valuation or quotation that survives scrutiny from one that becomes the next dispute.

Frequently Asked Questions

How do you price a variation order under a JCT contract?

You work through the clause 5.6 hierarchy: use existing contract bill rates if the work is similar in character and conditions, apply those rates with a fair allowance if conditions or quantity have changed significantly, use fair rates and prices if the work is genuinely dissimilar, or fall back to daywork under clause 5.7 if the work cannot be measured at all.

How do you price a compensation event under NEC4?

The Contractor submits a quotation forecasting the change to Defined Cost - using the Shorter Schedule of Cost Components under Options A and B, or the full Schedule of Cost Components under Options C, D and E - plus the Fee percentage stated in the Contract Data, along with any effect on the Completion Date.

What is the main difference between JCT and NEC when pricing a variation?

JCT values a variation retrospectively against contract rates once the work is measured, while NEC4 prices it prospectively before the work starts, through a Contractor's quotation based on forecast Defined Cost plus Fee. NEC also combines cost and time into one assessment; JCT keeps them separate.

Can a JCT contract use an NEC-style quotation approach?

Yes. The JCT Schedule 2 Quotation procedure is an optional mechanism that lets the Contractor submit an advance quotation for a variation before carrying it out, similar in spirit to an NEC compensation event quotation, though it remains an optional add-on rather than the default JCT method.

What happens if the Project Manager doesn't respond to an NEC4 quotation in time?

If the Project Manager fails to reply within the required period and does not extend it, the Contractor's quotation can be treated as having been accepted by default, which makes tracking the NEC4 timescales a critical discipline for the Project Manager's commercial team.

Is daywork the same thing as NEC's Defined Cost?

No. JCT daywork is a fallback valuation method for short-duration work that cannot be properly measured, priced on labour hours, plant time and materials plus a percentage addition. NEC's Defined Cost is a broader defined term covering the cost components of all the work in a compensation event, priced against a specific schedule in the contract, not just an exception mechanism.

Which method is fairer to the Contractor, JCT or NEC?

Neither is inherently fairer - they allocate risk differently. JCT's rate-based valuation gives the Contractor certainty from rates fixed at tender, but disputes often surface late, at final account. NEC's forecast-based quotation resolves price and time early, but shifts forecasting risk onto the Contractor and depends on both parties meeting tight response timescales.

Final Thoughts

Knowing how to price a variation order is really knowing which contract you're standing on. JCT's valuation hierarchy and NEC4's compensation event quotation are both coherent, well-tested systems - they simply start from different assumptions about when a price should be fixed and whether time and money belong in the same conversation. The QS who treats every variation the same way, regardless of form, is the one who ends up disputing figures at final account that could have been agreed in week two.

The practical takeaway is procedural discipline matched to the contract in front of you: measure and reference rates correctly under JCT, or forecast and quote on time under NEC4. Get the philosophy right first, and the arithmetic follows.

Want the full picture? Want the detail behind each method?

This guide compares the two approaches side by side - for the full JCT valuation mechanics, read How to Price Variations in JCT Contracts, and for the broader lifecycle of a variation on any project, see Variation Orders in Construction: A Complete QS Guide.