Valuation of money changing services: taxable value based on exchange rate differential or a prescribed presumptive percentage. Rule 2B prescribes that for money changing services involving Indian Rupees the taxable value equals the difference between the actual buying or selling rate and the Reserve Bank of India reference rate, multiplied by the currency units; if the RBI reference rate is unavailable a presumptive valuation applies as a fixed proportion of the gross Indian Rupees involved; where neither currency is INR, the taxable value is a presumptive fixed proportion of the lesser amount obtainable by converting either currency into INR at the RBI reference rate.