Telegraphic transfer buying rate governs tax deduction on foreign currency income payable outside India and in financial centres. For deduction of tax at source on income payable in foreign currency, the value in rupees is to be calculated at the telegraphic transfer buying rate on the date tax is required to be deducted. If that rate is not published, the last published rate may be used. The rule applies to income payable to an assessee outside India, to a Unit in an International Financial Services Centre, and to income paid by such a Unit to an assessee in India.