Commercial & Contract · Mandatory · Construction

Variation Instruction and Change Order

A formal instruction to the contractor to vary the works.

Last reviewed: 29 March 2026 — This guide reflects UK law as of this date. JCT / NEC / Contract remains current with no amendments enacted as of 29 March 2026. Next scheduled review: 29 March 2027.

Legal basis	JCT Standard Building Contract 2024 (Clause 3.14) + NEC4 Engineering and Construction Contract (Clause 60.1 & 61) + Express contract terms
JCT variations	Variations must be instructed in writing by the Contract Administrator — the contractor is not obliged to carry out work that has not been formally instructed
NEC4 compensation events	NEC4 does not use the term “variation” — changes are compensation events under Clause 60.1, requiring a formal Project Manager instruction
JCT 2024 updates	JCT 2024 introduces epidemic clauses and expanded ground conditions provisions, both of which may trigger variation instructions
CVI process	A Confirmation of Verbal Instruction (CVI) preserves the contractor's rights where instructions are given verbally on site

1. Variation Instruction

A variation instruction is the commercial trigger that authorises a change to the contracted scope of works. It is one of the most important documents in construction contract administration because it creates the contractual basis for additional cost, omitted work, or changes to the programme. Without a properly issued variation instruction, the contractor has no contractual entitlement to additional payment and the employer has no contractual mechanism to require changed work.

Under JCT 2024, variations are dealt with retrospectively — the Contract Administrator instructs a change under Clause 3.14, the contractor carries out the work, and the valuation follows under the valuation rules in Section 5. Under NEC4, the approach is prospective — the Project Manager instructs a compensation event under Clause 60.1, and the contractor is required to submit a quotation before the work is carried out wherever practicable. This fundamental difference in philosophy means that the variation instruction document serves a different purpose under each contract form, but the underlying principle is the same: no instruction, no entitlement.

JCT 2024 has introduced new grounds for variation including provisions relating to epidemics and expanded ground conditions. These additions reflect the lessons of recent years and mean that variation instructions may now be triggered by a wider range of circumstances than under previous editions. Contractors and contract administrators must be familiar with these new provisions to ensure that instructions are issued on the correct contractual basis.

Confirm verbal instructions in writing within 24 hours

Where an instruction is given verbally on site — which happens frequently in practice — the contractor should issue a Confirmation of Verbal Instruction (CVI) in writing within 24 hours. Under JCT, if the Contract Administrator does not dissent from the CVI within a reasonable period, the instruction is deemed to have been given in writing. Failing to confirm verbal instructions is one of the most common causes of disputes at final account stage because there is no written record of what was instructed.

2. Content

A properly drafted variation instruction must contain sufficient detail to identify the change, link it to the contract, and enable the contractor to price and programme the work. The following table sets out the essential content of a variation instruction document.

Field	Detail
Instruction number	Unique sequential reference number for the variation instruction (e.g. VI-001). Must be consistent with the project numbering system and cross-referenced in all subsequent correspondence, quotations, and valuations.
Date	Date the instruction is issued. This is critical for contractual time limits — under NEC4, the contractor must submit a quotation within 3 weeks of the instruction. Under JCT, the date establishes when the variation was instructed for valuation and programme purposes.
Issued by	Name, role, and organisation of the person issuing the instruction. Under JCT, only the Contract Administrator has authority to issue variation instructions. Under NEC4, only the Project Manager may instruct compensation events. Instructions issued by unauthorised persons have no contractual effect.
Contract reference	The specific contract clause under which the instruction is issued (e.g. JCT Clause 3.14, NEC4 Clause 60.1(1)). This establishes the contractual basis for the variation and determines the applicable valuation rules.
Description of variation	A clear, detailed description of the change to the works. Must be specific enough for the contractor to understand exactly what is required, what is being added, omitted, or changed. Vague descriptions lead to disputes.
Drawings and specifications	List of all revised drawings, specification clauses, and other documents that define the varied work. Drawing numbers, revision letters, and dates must be stated. The contractor must work to the documents listed in the instruction.
Approximate value	An estimate of the likely cost impact of the variation. This is not a binding valuation but assists with cost management and cash flow forecasting. Under NEC4, the contractor's quotation will establish the defined cost.
Programme impact	An initial assessment of whether the variation is likely to affect the programme, including any extension of time implications. Under NEC4, the quotation must include the programme impact. Under JCT, the contractor may separately claim an extension of time.
Valuation basis	The basis on which the variation will be valued — contract rates, fair rates, daywork, or other agreed method. Under JCT, the valuation rules in Clause 5.6 apply. Under NEC4, the variation is valued at defined cost plus the fee percentage.
Signature	Signature of the Contract Administrator (JCT) or Project Manager (NEC4) confirming the instruction. The instruction is not valid without the signature of the authorised person.

3. Common Mistakes

Allowing work to proceed without a formal instruction

One of the most damaging commercial mistakes a contractor can make is carrying out varied work without a written instruction in place. In practice, this happens frequently — the client or architect requests a change on site, the contractor proceeds in good faith, and the instruction is never formalised. At final account stage, the employer may dispute that the work was ever instructed, and the contractor is left with no contractual basis for payment. Under JCT, the contractor is not obliged to carry out work unless it has been instructed in writing by the Contract Administrator. Under NEC4, work carried out without a compensation event instruction has no contractual status. The commercial discipline of insisting on a written instruction before work starts is fundamental to protecting the contractor's financial position.

Verbal instructions without written follow-up

Verbal instructions are a daily reality on construction sites, but they create significant commercial risk if they are not confirmed in writing. The contractor should issue a Confirmation of Verbal Instruction (CVI) within 24 hours of receiving any verbal instruction that changes the scope, cost, or programme. Under JCT, if the Contract Administrator does not dissent from the CVI, the instruction is deemed to have been given. Under NEC4, the contractor should notify a compensation event under Clause 61.3 if the Project Manager has not formally instructed it. Failing to follow up verbal instructions in writing is a recurring cause of final account disputes and can result in the contractor absorbing costs that should properly have been paid as variations.

4. Frequently Asked Questions

Can the employer refuse to instruct a variation?▾

Under JCT, the power to instruct variations belongs to the Contract Administrator, not the employer directly. However, the employer funds the project and the Contract Administrator will generally act on the employer's instructions. The employer is not obliged to instruct any variation — it is entirely within the employer's discretion whether to change the scope of the works. If the contractor identifies a need for a change (for example, due to unforeseen ground conditions or a design issue), the contractor can request a variation instruction, but the Contract Administrator is not obliged to issue one unless the contract requires it. Under NEC4, the Project Manager instructs compensation events, and the employer can choose not to proceed with a proposed change. The key point is that a variation is a voluntary change to the works — the employer cannot be compelled to instruct one, but equally the contractor cannot be required to carry out changed work without a formal instruction.

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