The amount an uncovered (naked) option seller (writer) is required to deposit and maintain to cover his or her daily position valuation and reasonably foreseeable intraday price changes. See Margin Tutorial Merrill Lynch Direct Margin Tutorial. Note: Options involve risk and are not suitable for all investors. Clients should understand thoroughly the risks and opportunities associated with trading options and should read the document entitled Characteristics and Risks of standardised Options before engaging in any options transactions.