Service tax

is service tax payable on abbetment basis on the whole amount payable to the developer including the cost of undivided share of the land or only on the portion of the amount payable as per construction agreement which may be about 60 % of the total cost of the flat

can a buyer get into tgwo separate agreemnent one for sale of undivided share in gthe land and other one for construction of the apartment  and pay service tax only on consgtruction portion

thanks in advance