I am with IB HK. For each future contract there is a margin requirement. Questions: Is this margin requirement need to be in cash or is it just an increase in the account initial/maintenance margin? For example if I have 100k ELV but 0 cash, will I be charged interest due to the margin requirement? I understand that if the position goes against me I will lose cash, but how about the initial margin? If the margin need to be in cash, how do I make sure I have enough cash, so that I don't need to pay interest to IB? Is the available cash reduced when I open the position?