When you enter a market order your trade will execute at the prevailing market price. A market order will be filled at the best available price at the time of entry, and can be used when execution speed is a priority over the price of execution.
Buying Power cushion for market orders
Your buying power is the money you have available to buy options. If you use limit orders, you can place any order(s) whose total price is below your buying power. Please note - if you use a market order, you must have buying power equal to at least 1.3x the price of the option. This ensures you can cover any increase in the option price due to a sudden market move upon placing your order.
For example, if an option is trading at $100 per contract, you would need $130 available in Buying Power to enter a market order.
The default order type is Market. To change any order from Market to Limit, simply click the arrow next to “Market” and toggle to limit. A pop-up window will appear, allowing you to pick a limit price.