Matching Orders

Order matching is the automated process by which a stock exchange's trading system pairs buy orders with sell orders for the same security — executing trades when a buyer's bid price meets or exceeds a seller's ask price. In India, NSE and BSE use an electronic limit order book matching system that operates on strict price-time priority — orders at better prices (higher bids, lower asks) are matched first, and among orders at the same price, earlier orders are matched before later ones. The exchange's matching engine continuously scans all outstanding orders in the order book and executes trades instantaneously whenever a compatible buy-sell pair is identified. During the pre-open call auction session (9:00 AM to 9:15 AM), all orders are accumulated and matched simultaneously at a single equilibrium price that maximises traded volume — a different process from the continuous matching during the regular session. The matching engine processes millions of orders per second on NSE, making it one of the fastest exchange systems globally. For investors, understanding order matching logic helps in selecting appropriate order types — market orders are matched immediately at the best available price, while limit orders wait in the book until a matching counterparty order arrives at the specified price.