If cash margin is posted, the required deposit is the current market value of the option plus 4 percent of the value of the underlying foreign currency.  This requirement is reduced by any amount the option is out of the money, to a minimum requirement of the premium plus .75 percent of the value of the underlying foreign currency. These percentages can be changed by the exchanges based on currency volatility.  Thus, as the market value of the option changes, the margin requirement will change.  So an option writer faces daily cash flows associated with changing margin requirements.
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