What Changed from NEC3 to NEC4

This chapter serves as a transition guide for practitioners moving from the third edition of the New Engineering Contract (NEC3) to the fourth edition (NEC4). The shift in terminology from Employer to Client and from Works Information to Scope is the most visible change, but the structural changes carry more administrative weight. The mutual trust obligation has been moved from clause 10.1 to a standalone clause 10.2 obligation. The Risk Register has been replaced by the Early Warning Register, which now carries one-week and two-week start-up deadlines under clause 15.2. Four substantive amendments restructure the compensation event framework, including the new dividing date that anchors actual against forecast cost in the assessment. Deemed acceptance is introduced for the programme, and the dual Fee has collapsed to a single Fee with fee-on-fee exposure across the Main Options. New material runs throughout. NEC4 introduces a contractual quality management system, four new secondary options with X15 substantively redrafted, a formalised Senior Representatives stage, the Option W3 Dispute Avoidance Board, and the clause 53 conclusive evidence provision. A summary table cross-references each change to the chapter that carries the detail.