How does NEC4 improve on NEC3 in terms of auditing Defined Cost?

The NEC4 cost-based contracts, i.e. main options C, D, E and F include a procedure for the Contractor to instigate a review and acceptance of its Defined Cost by the Project Manager. This new procedure should encourage the checking and agreement of Defined Cost and Disallowed Cost as the works or services are progressing, rather than leaving the exercise to the end. This brings much more cost certainty to the cost-based contracts which is better for both parties.