There are two kinds of empty positions. One case is that after the futures customers close their positions, they still owe money to the futures exchange, that is, the account is floating, the tax revenue is reduced, and the profit and loss is higher than the total account funds, that is, the customer's equity is lower than 0.
Due to the rapid changes in the market, the deposit in the account can no longer maintain the original contract before the investor adds the deposit. This kind of margin "zeroing" caused by forced liquidation due to insufficient margin is commonly known as "short position", and the meaning of "short position" is the same as "short position".