What does NEC4 clause 60.1(1) mean?

It is NEC's version of a variation. The Scope is the description of your work and the limits on how you do it, including any design you supply. In the NEC4 main contract the Project Manager gives the instruction. On an NEC subcontract your main contractor does. To rely on this clause, show three things. There was an instruction. It came from your main contractor. And it changed the Scope as it stood. A drawing revision issued without an instruction does not count. Nor does a change you proposed to suit your own design. Because the event comes from its own instruction, your main contractor should notify it when it gives the instruction, and ask you to quote. If it does not, you notify under clause 61.3. The 8-week bar does not apply, because your main contractor should have notified it. The change to the Prices, your contract price, is assessed under clause 63.1. It is the effect of the instruction on actual Defined Cost for work done by the date of the instruction. Add forecast Defined Cost for work still to do, plus the Fee. So an omission cuts your price and an addition raises it, both with the risk allowances clause 63 requires. Two things go wrong most. The change is priced from the activity schedule or bill of quantities instead of from Defined Cost. Or your main contractor argues you caused the change, when the Scope itself was unclear. Any delay to the Completion Date is assessed separately under clause 63, and that is a job for your planner.