There are Taker Fees and Maker Fees when trading on BitMEX. Taker Fees are charged when you are the taker in a trade and Maker Fees are charged when you are the maker.
“Taker'' is an order that trades at a market price, “Maker” is an order that trades at a limit price. When submitting orders, BitMEX assumes the highest fee based on the appropriate fee tier and locks the total order amount + fees.
For example, if a user places a buy order of 1 XBT at 40,000.00 USDT, the system will check if the user has sufficient balance to execute this trade, with the fee rate of 0.1%, the user will need to have at least 40,040.00 USDT in their wallet to submit this trade; if the actual fee amount when the order is filled is lower than the assumed fees, the residual will be refunded to the user.