Extension of time: the notice comes first
A good delay claim is lost more often on the notice than on the merits. Under AS 4000 the entitlement and the paperwork travel together, and the paperwork has a deadline.
QScope Team · 22 May 2026 · 6 min read
Under AS 4000 a contractor delayed by a qualifying cause can claim an extension of time, which moves the date for practical completion and shields against liquidated damages for that period. The entitlement is real, but it is conditional, and the first condition is a notice served on time.
What has to line up
- A qualifying cause of delay. A cause the contract recognises as entitling the contractor to more time, rather than one at the contractor's own risk.
- Effect on the critical path. The delay must actually push practical completion, not just disrupt a non-critical activity.
- A notice in time. Written notice of the delay within the period the contract requires, giving the cause and the likely effect.
Why the notice is the hinge
AS 4000 ties the claim to timely notice. Serve late and the Superintendent may be entitled to reduce or refuse the extension, however genuine the delay. This is not the Superintendent being difficult. It is the contract giving the principal a fair chance to see the delay while it is happening and to respond, rather than learning of it months later in a claim.
Notice, then substantiation
The first notice is not the whole claim. It flags the event. The substantiation follows: the programme showing the critical path, the records showing the cause, and the assessment of the days. Keeping the two separate matters, because the deadline bites on the notice, not on the fully worked-up claim. Notify inside the window, then build the case.
Concurrency and float
Where two causes of delay overlap, one at the contractor's risk and one at the principal's, the assessment gets harder and the records get more important. So does float: a delay that only eats spare time in the programme may not move practical completion at all. The assessment is about the completion date, not about any single late activity.
Time and money are separate questions
An extension of time protects the completion date and the position on liquidated damages. It does not by itself pay the delay costs. Prolongation and delay cost are a separate claim under the contract, assessed on their own basis. Winning the time does not automatically win the money, and the two should be pleaded and recorded as distinct entitlements.
The habit
Log every delay event the day it appears, against its notice deadline, and keep the programme current enough to show the critical path. An extension of time is an evidence exercise won in real time, not a story assembled at the end.
QScope logs each delay event against its notice deadline and tracks the extended date for completion, so an entitlement is never lost to a notice served too late.