NEC4 Option B - application of credits for reduced/ omitted work after Completion

Having rejected the Contractor’s CE quotation for an event which arose from a PM instruction, the PM prepared its own assessment and issued this to the Contractor one day before its due date. During the period of assessment the PM also issued the Completion certificate for the project. Can the PM now:

  1. Apply reductions to the original contract sum/ BOQ for omissions related to this CE, but which it did not include in its assessment (now that the period of assessment is passed)?
  2. Apply reductions the original contract sum/ BOQ for the above or any omitted work, when it has not raised a CE for same prior to issue of the Completion certificate?