A limit order doesn't become a market order, so you won't pay more or sell for less than you want. But if a price changes quickly, your order may not go through even if the price was actually at the limit for a time. A GTC has traditionally lasted until it was either filled or you cancelled it. But some firms now keep them on the books for only 90 days before they expire. A day order is canceled automatically if it isn't filled by the end of the trading day.
Discount brokers carry out transactions for clients, but typically offer more limited services.
Their fees, however, are usually much lower than full-service brokers'. And for experienced investors who trade often and in large blocks of stock, there are deep discount brokers , whose commissions are even lower. The cheapest way to trade securities, however, is usually with an online brokerage firm . Many established full-service and discount brokerage firms offer substantial discounts to their customers who buy and sell online. And other firms operate exclusively online.