6.—(1) Any transfer under regulations 12, 14 and 15 (except of retained dwellings) shall be for the amount (which may be a negative amount) determined in the final valuation.
(2) Any other transfer of property under these Regulations shall be for an amount (which may be a negative amount) equal to the price which, on the basis of the assumptions described in regulation 17(3), it would realise if sold on the open market by a willing vendor.