Post-Only Order is used by traders who would like to ensure that they could receive a maker rebate when this limit order is filled. In other words, this order can only be placed if it will enter the Order Book, rather than executed immediately. Orders in Order Book are regarded as market-making orders, as they provide liquidity to the market. On the other hand, orders that are filled immediately are regarded as market taking orders as they take liquidity from the market.
Even if one contract of the order can be executed immediately, this Post-Only order will be cancelled by the system automatically. Some traders prefer this type of order when they are sensitive about the transaction fees, especially large volume orders or using scalping strategy.
DueDEX users can tick the box beside "Post-Only" to initiate the feature when placing a Limit Order, Stop Limit Order or Take Profit Limit Order.
Post-Only Order Example
1. Without Post-Only selection
When a trader places an order to sell short of 1000 contracts at the price of US$8,484, at this market, 568 contracts will be filled immediately, and the other 432 contracts will enter into the Order Book. 568 contracts are regarded as market taking; therefore, a trading fee will be charged.
2. With Post-Only selection
(1) The same trader would like to place an order to sell short of 1000 contracts at the price of US$8,484, with Post-Only ticked. When he confirms this order, immediately, he will receive an error message notifying him that this order isn't placed at all.