VENSAV3150 - meaning of the “open market value of the supply of the materials” and the “cost of the total supply”
The “open market value of the supply of the materials” referred to the price that an installer of energy-saving materials would have had to pay (excluding VAT) to purchase the materials on the open market. In practice, this was normally the price that the installer pays its own supplier for the materials. The inclusion of the term “open market value” was intended to guard against the artificial undervaluation of materials.
The “cost of the total supply” was the total charge (excluding VAT) made to the customer (i.e. the total value of the supply of installing the energy-saving materials).