What does NEC4 clause 60.1(18) mean?

It is the sweep-up event for the other side's defaults. Its purpose is to keep those breaches inside the contract's own procedure. The breach is notified, quoted and assessed like any other event. The 8-week bar, the decision under clause 61.4 and the Defined Cost basis all apply. To rely on the clause, show three things. First, an obligation in the contract, meaning the conditions, the Contract Data or the Scope, not a general hope of cooperation. Second, that the Client itself failed to meet it, not the Project Manager, the Supervisor or Others. On a subcontract, that is your main contractor. Third, that the failure is not already one of the other compensation events. If it is, that paragraph applies instead. So this clause only catches what the others leave. Examples are failing to give a consent only the other side can give, or to keep up an insurance the contract requires it to hold. Notify under clause 61.3 within 8 weeks of becoming aware of the breach. The change to the Prices, your contract price, is assessed under clause 63.1. It is the effect on actual Defined Cost up to the notification and forecast Defined Cost after it, plus the Fee. It is a cost-based assessment, not damages, so loss of profit on other work and similar items do not come in. Two things go wrong most. Something the Project Manager did is described as a Client breach, when those failures have their own paragraphs. Or the breach is notified in general terms, without naming the obligation broken. Any delay to the Completion Date is assessed separately under clause 63, and that is a job for your planner.