Market-to-limit conversion in the pre-open session

Sun, 21 Jun 2026 00:00:00 +0000

Market-to-limit conversion in the pre-open session is the National Stock Exchange mechanism by which a market order placed during the pre-open call auction is first reckoned for the day’s equilibrium price and then, for any quantity that does not match in the auction, modified into a limit order priced at that discovered equilibrium price and carried into the normal market. The pre-open session runs from 9:00 to 9:15 before the continuous market opens, and its purpose is single-price discovery: the auction settles every pre-open trade at one equilibrium price, which becomes the day’s open. Because that auction matches at a single price rather than continuously, a market order cannot remain price-less once the auction ends; the exchange assigns it the equilibrium price so that any unmatched part can enter the continuous order book.

Market to Limit on WebNotes

Market-to-limit conversion in the pre-open session