Commercial & Contract · Best Practice · Construction

Extension of Time Claim

A claim for additional time to complete the works due to a relevant event.

Last reviewed: 29 March 2026 — This guide reflects UK law as of this date. JCT / NEC 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 2.26–2.29) + NEC4 Engineering and Construction Contract (Clause 60–65) + Express contract terms
Purpose	An extension of time (EOT) adjusts the completion date to account for employer-caused or neutral delay events, preventing the imposition of liquidated damages for delay that is not the contractor's fault
JCT Relevant Events	Include variations, late information, opening up and testing, adverse weather, epidemic (new in 2024), force majeure, civil commotion, and statutory undertakers' work
NEC4 time bar	Under NEC4, the contractor must notify a compensation event within 8 weeks of becoming aware of it — failure to notify within 8 weeks means the claim is time-barred
JCT 2024 response	The Contract Administrator has 8 weeks from receipt of sufficient particulars to give a decision on the contractor's extension of time application

1. Extension of Time

An extension of time claim is one of the most important documents in construction contract administration. Its purpose is twofold: it protects the contractor from liquidated damages for delay that is not the contractor's fault, and it preserves the employer's right to deduct liquidated damages for delay that is the contractor's fault. Without an extension of time mechanism, any employer-caused delay would set time at large, meaning the contractor would only need to complete within a reasonable time and the employer would lose the right to deduct liquidated damages entirely.

Under JCT 2024, the extension of time provisions are contained in Clauses 2.26 to 2.29. The contractor must notify the Contract Administrator of any delay event as soon as it becomes reasonably apparent that the progress of the works is being or is likely to be delayed. The contractor must provide particulars of the expected effects, including an estimate of the expected delay to the completion date. The Contract Administrator then has 8 weeks from receipt of sufficient particulars and the contractor's estimate to give a decision, either granting an extension of time, refusing it, or granting a shorter extension than claimed.

JCT 2024 has expanded the list of Relevant Events to include epidemics, reflecting the experience of the construction industry during the COVID-19 pandemic. This addition means that future epidemic-related delays may qualify for an extension of time, provided the contractor complies with the notification requirements. The 2024 edition also includes expanded provisions relating to ground conditions.

Under NEC4, delay is dealt with through the compensation event mechanism. Where a compensation event causes delay, the contractor's quotation must include the effect on the planned completion date. The critical difference is the NEC4 time bar: the contractor must notify a compensation event within 8 weeks of becoming aware of it. If the contractor fails to notify within 8 weeks, the event is deemed not to have happened, and the contractor loses all entitlement to additional time and cost. This is one of the strictest time bar provisions in UK construction contracts.

The extension of time claim is also the foundation for delay analysis. Whether using impacted as-planned, time impact analysis, windows analysis, or collapsed as-built methodology, the claim document must demonstrate the causal link between the delay event and the impact on the completion date. A claim that simply states a delay occurred without analysing its effect on the critical path is unlikely to succeed.

NEC4: notify within 8 weeks or the claim is time-barred

Under NEC4 Clause 61.3, if the contractor does not notify a compensation event within 8 weeks of becoming aware of it, the Project Manager is not required to consider it and the event is treated as if it had not occurred. This is an absolute time bar — there is no discretion and no exception. The contractor loses all entitlement to additional time, additional cost, and any adjustment to the completion date. The 8-week clock starts from the date the contractor became aware of the event, not from the date of the event itself. Contractors working under NEC4 must have rigorous systems in place to identify and notify compensation events promptly.

2. Content

An extension of time claim must set out the delay event, the contractual basis for the claim, the delay analysis, and the extension sought. The following table sets out the essential content of an extension of time claim document.

Field	Detail
Delay event	A clear description of the event causing or likely to cause delay to the works. Must be specific — not simply “late information” but identifying exactly what information was late, when it was due, when it was received, and what work was affected.
Notification	Date the delay was first notified to the Contract Administrator (JCT) or Project Manager (NEC4). Under JCT, notification must be given as soon as delay becomes reasonably apparent. Under NEC4, notification must be within 8 weeks of awareness. Include the reference number of the notification letter or email.
Contractual basis	The specific contract clause relied upon for the extension of time claim. Under JCT, this is the relevant Relevant Event in Clause 2.26 (e.g. Clause 2.26.1 for variations, Clause 2.26.2 for late instructions). Under NEC4, this is the relevant compensation event in Clause 60.1.
Delay analysis	The technical analysis demonstrating how the delay event affects the critical path and the completion date. This may include impacted as-planned analysis, time impact analysis, windows analysis, or collapsed as-built analysis depending on the complexity of the claim. The analysis must show the causal link between the event and the delay to completion.
Extension claimed	The number of days or weeks of extension of time being claimed. This figure must be derived from the delay analysis, not simply estimated. The extension claimed should represent the actual delay to the completion date caused by the event, net of any concurrent delay where applicable.
Programme extract	An extract from the project programme showing the activities affected by the delay event, the critical path, and the impact on the completion date. The programme should be the current accepted programme at the time the delay event occurred, not a retrospective reconstruction.
Supporting records	Contemporaneous records supporting the claim: site diaries, progress photographs, correspondence, meeting minutes, RFIs, drawing issue records, weather records (for adverse weather claims), and any other documents that evidence the delay event and its impact on progress.
Concurrent delay	An assessment of whether any contractor-caused delay was running concurrently with the employer-caused delay event. If concurrent delay exists, the claim should address how it has been dealt with. Under English law (Malmaison), the contractor is generally entitled to an extension of time even where concurrent delay exists, provided the employer-caused event is an effective cause of the delay.
Submitted by	Name, role, and signature of the person submitting the claim on behalf of the contractor, together with the date of submission. The claim should be submitted by or on behalf of a person with authority to make contractual notifications.

3. Common Mistakes

Not notifying delays as they arise

The most common and most costly mistake in extension of time claims is failing to notify delay events as they arise. Under JCT, the contractor must give notice as soon as it becomes reasonably apparent that progress is being or is likely to be delayed. Under NEC4, failure to notify within 8 weeks is an absolute time bar. In practice, many contractors are reluctant to submit delay notifications because they fear damaging the commercial relationship with the employer or the Contract Administrator. This is a false economy. A delay notification is a contractual requirement, not a complaint. Failing to notify means the contractor may be unable to claim an extension of time, may face liquidated damages for delay that was not the contractor's fault, and may lose the contemporaneous evidence that is essential for a successful claim. Delay notifications should be submitted promptly, factually, and without emotion.

Claiming extension of time without programme analysis

An extension of time claim that does not include a delay analysis demonstrating the impact of the delay event on the critical path is fundamentally deficient. Simply stating that a delay event occurred and claiming a number of days is not sufficient — the contractor must demonstrate the causal link between the event and the delay to the completion date. This requires programme analysis: identifying the affected activities, showing that they are on or near the critical path, and quantifying the delay to the completion date. Without this analysis, the Contract Administrator or Project Manager has no basis on which to assess the claim and is likely to reject it. The type of analysis used (impacted as-planned, time impact, windows, or collapsed as-built) should be proportionate to the complexity and value of the claim, but some form of programme-based analysis is essential for every extension of time claim.

4. Frequently Asked Questions

What is concurrent delay and how does it affect an extension of time claim?▾

Concurrent delay arises where two or more delay events occur at the same time, one of which is the employer's risk (a Relevant Event under JCT, or a compensation event under NEC4) and one of which is the contractor's risk (such as a shortage of labour or a sub-contractor delay). The question is whether the contractor is entitled to an extension of time when both events are operating simultaneously. Under English law, the leading authority is the Malmaison approach, which provides that where an employer-caused delay event and a contractor-caused delay event operate concurrently, and both are effective causes of the delay to completion, the contractor is entitled to an extension of time for the employer-caused event. The contractor does not lose the right to an extension simply because there is a concurrent contractor delay. However, the contractor must still demonstrate that the employer-caused event is an effective cause of the delay to the completion date — if the contractor delay alone would have caused the same delay regardless of the employer event, no extension is due. Concurrent delay is a complex area and the analysis must be carried out carefully using programme-based delay analysis methods.

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