Extended hours

Dealing in listed shares outside the venue's primary session, in a window before the opening auction and another after the close. Orders are matched on electronic venues rather than through the exchange's usual continuous book, the participants are mostly institutions and brokers offering access, and the windows and rules are set by each venue rather than being uniform across markets.

Conditions in those windows differ in kind, not just in degree. Far fewer orders rest at each price, so quoted spreads are wide, a modest order moves the price further than it would in the session, and a print can occur some distance from the last regular-session price without much behind it. Many order types are restricted to limit orders precisely because of this. The price printed in extended hours is not the official closing price of the share, which is struck in the closing auction.

The point that matters for a contract written on a share is that the contract can only be quoted while its underlying is being priced. Providers commonly quote such contracts during the primary session only, and some stand aside from the opening and closing auctions as well. Results and company announcements are frequently released into these windows for that reason, so a share can move substantially while a contract on it is not quotable, and the gap between the previous close and the next open is where that movement shows up.