What is after-hours trading?

A company reports its quarterly results at 4:15 PM. The stock closed at $60.00, but after hours it trades at $66.00 on the news. You place a limit order to sell 50 shares at $65.50. A trade reaches $65.50, and your order fills for $3,275.

A market order would have been riskier: with fewer buyers and sellers, the next trade can be far from the last one. The next morning the stock may open higher, lower or close to where it traded after hours.

On JagSim, a stock limit order can fill after the close, from 4:00 PM to 8:00 PM New York time (to 5:00 PM on a half day), if you tick "Fill during pre-market and after-hours" when you place it. Market orders and stop orders for stocks never fill outside the regular session; they wait for the next open. A Day order with the box ticked still ends at the next regular close. JagSim sees fewer trades after the close, and an order fills only on a trade it sees. How trading works on JagSim.

Reading the after-hours price as the next open. A few trades after the close can be far from where the stock opens in the morning.

Forgetting how thin it is. Fewer people trade after hours, so one order can move the price a long way and a limit may not fill.

What are the after-hours trading times?

In the US, usually 4:00 PM to 8:00 PM New York time, Monday to Friday. Each broker sets its own window inside that.

Why is after-hours trading riskier?

Fewer people trade, so the gap between the bid and the ask is wider and one trade can move the price a lot. News released after the close can also move a stock sharply.

Can I use a market order after hours?

Most brokers accept only limit orders outside regular hours. On JagSim, only a limit order with the extended-hours box ticked can fill then.

Does the after-hours price predict the next open?

Not reliably. It reflects the few trades made after the close, and the next morning's open can be higher, lower or the same.