"The test is were the goods or services which were supplied to the taxpayer used or to be used for the purposes of any business carried on by him? The test is a subjective one: that is to say, the fact-finding tribunal must look into the taxpayer's mind as it was at the relevant time to discover his object. Where the taxpayer is a company, a relevant mind or minds are those of the person or persons who control the company or are entitled to and do act for the company. "