When you sell options, you receive premium which will be used when placing an options buy order. If you have received a premium and you try to place a new options buy order, the required margin will show as zero if it's less than the premium you received. Here are the scenarios where this might happen:
Fresh options short premium credit received: If you receive a premium of ₹20,000 from selling options and the required margin for your new buy order is less than ₹20,000, the margin requirement will display as zero. Your order will still be placed successfully.
Premium received post intraday option positions closed: For example, if you receive ₹15,000 as a premium after closing intraday options positions and the required margin for a new buy order is ₹10,000, the margin requirement will show as zero.
Premium received after closing the carry forward options buy position: For example, if you receive ₹18,000 as a premium after closing a carry forward options buy position and the required margin for a new buy order is ₹12,000, the margin requirement will show as zero.
However, if the margin required for the new buy order is more than the premium received, the difference between the premium received and the required margin will be displayed in the order window and will be utilized from the available funds on placing the order.
For example, if you received a premium of ₹20,000 but the required margin for your new buy order is ₹25,000, the margin requirement displayed in the order window will be ₹5,000 (₹25,000 - ₹20,000), which will be utilized from your available funds on placing the order.