Mr/Ms. Srawat,
Under Section 3 of the Welfare Cess Act, these construction companies are liable to the levy of a Cess at a rate not exceeding two per cent, but not less than one per cent, of the cost of construction incurred. ... It is clear that the Cess can only be levied for the purposes of the BOCW Act
It has to be calculated from the invoice (exclusive of taxes)