The NSE trading system provides complete flexibility to members in the kinds of orders that can be placed by them. Orders are first numbered and time-stamped on receipt and then immediately processed for potential match. Every order has a distinctive order number and a unique time stamp on it. If a match is not found, then the orders are stored in different 'books'. Orders are stored in price-time priority in various books in the following sequence:

-Best Price
-Within Price, by time priority.

Price priority means that if two orders are entered into the system, the order having the best price gets the higher priority. Time priority means if two orders having the same price are entered, the order that is entered first gets the higher priority.

The Equities segment has following types of books:

Regular Lot Book
The Regular Lot Book contains all regular lot orders that have none of the following attributes attached to them.
- All or None (AON)
- Minimum Fill (MF)
- Stop Loss (SL)


Special Terms Book
The Special Terms book contains all orders that have either of the following terms attached:
- All or None (AON)
- Minimum Fill (MF)
Note: Currently, special term orders i.e. AON and MF are not available on the system as per the SEBI directives.


Negotiated Trade Book
The Negotiated Trade book contains all negotiated order entries captured by the system before they have been matched against their counterparty trade entries. These entries are matched with identical counterparty entries only. It is to be noted that these entries contain a counterparty code in addition to other order details.


Stop-Loss Book
Stop Loss orders are stored in this book till the trigger price specified in the order is reached or surpassed. When the trigger price is reached or surpassed, the order is released in the Regular lot book.

The stop loss condition is met under the following circumstances:
Sell order - A sell order in the Stop Loss book gets triggered when the last traded price in the normal market reaches or falls below the trigger price of the order.

Buy order - A buy order in the Stop Loss book gets triggered when the last traded price in the normal market reaches or exceeds the trigger price of the order.


Odd Lot Book
The Odd lot book contains all odd lot orders (orders with quantity less than marketable lot) in the system. The system attempts to match an active odd lot order against passive orders in the book. Currently, pursuant to a SEBI directive, the Odd Lot Market is being used for orders that have quantity less than or equal to 500 viz. the Limited Physical Market.


Spot Book
The Spot lot book contains all spot orders (orders having only the settlement period different) in the system. The system attempts to match an active spot lot order against the passive orders in the book. Currently the Spot Market book type is not in use.


Auction Book
This book contains orders that are entered for all auctions. The matching process for auction orders in this book is initiated only at the end of the solicitor period.

Market Types | Order Matching Rules | Order Conditions