The PM descopes part of the works on a scheme running under ECC option A. Do I keep the item in the activity schedule and show my defined costs for the full works against my defined costs for descoped works and show the negative at the bottom of the activity schedule?
Under clause 54 the Contractor is allowed to submit a revised activity schedule if it no longer reflects how they plan to carry out the works. The only reasons not to accept that revised schedule is that it is not in line with the programme, does not add up to the right number or costs are not “evenly” distributed.
Any compensation event is normally added to the activity schedule - but in this case there probably needs to be an amendment to the original item as that will no longer be carried out (and the Contractor can not claim against it). The Contractor is fairly quiet on specifically how this should be done - but you would hope both Parties would be able to come to a sensible agreement as to how it should look to reflect the implemented compensation event.
Also worth pointing out that an instruction to change to WI that is a single line on the activity schedule you do not use that activity schedule rate UNLESS both Parties agree. It would be assessed from first principles using Defined Cost.