What happens if I miss the 8 week deadline for a compensation event?

Start with the wording, because the 8 week bar in the unamended NEC4 form does not catch everything. The bar applies to events the contractor should have notified: things like weather, ground conditions or third party interference. It does not apply to events arising from the Project Manager or Supervisor giving an instruction, issuing a certificate or changing an earlier decision, because those the Project Manager is required to notify, and the contractor's failure to notify them does not kill the entitlement. So the first salvage question is always which side of that line the event sits on: a change that was instructed but never processed by anyone is usually still alive. If the event genuinely sits on the barred side and the weeks have run, the honest position is that the contractual entitlement has lapsed, and what remains is negotiation: events already recorded in early warnings, minutes and programmes are hard for a Project Manager to pretend never happened, and many accounts settle with barred events priced at a discount rather than at zero. What does not work is silence followed by a final account surprise. Whatever the position, notify now rather than later: a late notification the other side must answer beats an event that only ever existed in your own files.

Say an earthworks subcontractor finds contaminated ground in February, deals with it, and first mentions money in June, week 16. If the contamination is an event it should have notified, the 8 week bar has closed over it, and its leverage is now the early warning it did raise and the Project Manager's own site diary, traded into a discounted settlement. But its second event, extra work from a site instruction that was never processed, survives untouched: instructions are the Project Manager's to notify, so the subcontractor notifies it in June and the machinery runs. One meeting, two events, opposite outcomes. The lesson is that a missed 8 weeks is not always fatal, but finding out which kind of event you hold should happen now, not at the final account.