This is incorrect. It's not that you need initial margin at the 'moment you purchase the contract', then the margin falls to maintenance level. At the moment you purchase the futures contract you only need to have the day margin that your broker requires. You need to have the Initial Margin ($4,500 for ES) when the market closes the first day you establish the position. 'initial Margin' and 'Overnight Margin' are often used interchangeably. If you meet the initial Margin that first day, your position then only requires Maintenance Margin ($3,600) to hang onto. However that doesn't really 'free up' $900 to use for new positions. It doesn't become 'margin excess'. It just gives you some leeway for that position to go against you before you have to liquidate or send more funds. If your equity falls below the $3,600 Maintenance Margin, you'll then be called upon to deposit funds to bring the equity back over the Initial Margin of $4,500. I think that covers it. Feel free to contact me directly if I can answer any more questions. Best regards,