A Day Order is a stipulation placed on an order to a broker to execute a trade at a specific price that expires at the end of the trading day if it is not completed. The main benefit of using this type of order is that it guarantees the trader will get their desired price, as long as the trade can be executed before the market closes for the day.If there is any slippage (the difference between where you want to buy/sell and where your order actually gets filled), then your order will automatically expire at market close. This feature can help protect traders from adverse moves in prices late in the trading session, which could cause them to miss out on their desired fill price.