Valuation of construction service: builders must value flats given to landowners by comparable sale prices, following Board guidance. In tri partite development arrangements where a landowner transfers land or development rights to a builder in return for flats, the value of construction service to the landowner is to be determined by reference to the price of similar flats charged by the builder to other purchasers, using comparable sales nearest the date when land or rights are made available; service tax on such construction is payable when possession or rights in the flats are transferred by conveyance, allotment letter or similar instrument.