NEC3 ECC: Can you reopen a CE once the quotation has been accepted?

CEs for works which have delayed the works were assessed without time implications and agreed. Programmes were submitted and approved which moved the planned completion date beyond the contract Completion Date. Can the CEs be reopened to assess the additional costs for preliminaries for completion after the Completion Date?
Option A Priced Activity Schedule.

The short and simple answer is no.

Once implemented (and I’m assuming they have been due to your comment that they have been agreed) quotations cannot be revised – see clause 65.2.

The only exception to this is if the quotation was based on a PM’s assumption which has proven to be incorrect.