Valuation of free services: taxability arises when benefit substitutes consideration; substance over form determines taxable nexus. Services supplied without monetary consideration are ordinarily outside the charge to service tax where no value can be attributed; however, if a gratuitous supply confers a measurable benefit to the provider or substitutes for remuneration, it may be treated as consideration and brought within the taxable base, with evidentiary nexus, disclosure of perquisites, and indicators of planned evasion being decisive factual elements in valuation.