It depends partly on how the settlement is worded but it is not so much an issue with para 8 Schedule 4 but whether the apportionment between the various items is just and reasonable ie commercially defendable, under para 4 Schedule 4. A formal valuation is not strictly required but it sounds as though you are sufficiently concerned about the split to make it prudent to request some type of short-form or “desktop” or “drive-by” valuation to protect yourself in the event of a negligence claim and/or HMRC alleging improper behaviour.