Payment, Defined Cost and Disallowed Cost

This chapter sets out the payment mechanism of NEC4, from periodic assessment to the final account. The assessment cycle under clauses 50 and 51 is set out in turn, with the one-week certification window after each assessment date, the three-week payment window that follows, and the daily interest at clause 51.4 that runs when either deadline is missed. The amount due varies across the six Main Options. Defined Cost is built from the Schedule of Cost Components, qualified by the open-market test at clause 52.1, and on the cost-based Options, it is reduced by the Disallowed Cost categories that protect the Client. The clause 54 pain/gain share is set out with a worked example for Options C and D, and recurring disputes around the Fee are addressed. The chapter closes with the final assessment under clause 53, including the clause 53.3 conclusive evidence rule that closes the final account window.