Under s 8A(1)(a) of the Income Tax Act 58 of 1962, the 'exercise of a right to acquire a marketable security' occurs when a taxpayer accepts an option or offer to acquire shares, thereby bringing into existence a binding contract of purchase and sale, and not when the contract is subsequently performed by payment of the purchase price and delivery of the shares. The section is concerned with the action by the taxpayer that gives rise to a binding contract under which the taxpayer will be entitled, subject to compliance with the contract terms, to acquire the marketable security, whether acquisition by transfer occurs immediately or is postponed to a future date. In interpreting tax legislation, courts must examine the words in their context, including the apparent purpose of the provision, relevant background material including legislative history, administrative practice by revenue authorities, and subsequent amendments to the legislation. Where parties conclude a genuine contract with postponed performance, the fact that it is structured to minimize tax liability does not render it a simulation - simulation requires that the transaction itself be dishonest or non-genuine, not merely tax-motivated.