Trading index futures requires to post the initial margin that adjusts according to market price fluctuations. Customers trading futures have to ensure there are sufficient balance to meet the initial margin requirements set by the exchange before opening new positions. Maintenance margin is 80% of the initial margin. If customers incur floating losses as they open positions and their account margin is below the maintenance margin, they must immediately deposit funds so that the margin is restored back to initial level or above, otherwise the securities brokers have the right to close the open positions on behalf of the clients without prior notice. The margin requirements of account is determined by the overall risk of the portfolio with different futures and options contracts using the calculation method called the Standard Portfolio Analysis of Risk (SPAN) by Hong Kong Exchanges and Clearing Limited. This method of calculation eliminates part of the margin requirements as a result of the hedging positions, so customers holding different combinations of futures and options contracts may be required to post more or less for the overall margin. Customers must therefore be aware whether their account balance can sufficiently meet the initial margin requirements set by the exchange.