Section 21. Stock and marketable securities how to be valued.

Where an instrument is chargeable with ad valorem duty in respect of any stock or of any marketable or other security, such duty shall be calculated on 1[the market value of such stock or security.] 2[Provided that the market value for calculating the stamp-duty shall be, in the case of-- (i) options in any securities, the premium paid by the buyer; (ii) repo on corporate bonds, interest paid by the borrower; and (iii) swap, only the first leg of the cash flow.]