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Trading System


NSE operates on the 'National Exchange for Automated Trading' (NEAT) system, a fully automated screen based trading system, which adopts the principle of an order driven market. NSE consciously opted in favour of an order driven system as opposed to a quote driven system. This has helped reduce jobbing spreads not only on NSE but in other exchanges as well, thus reducing transaction costs.

The NEAT system has four types of market. They are:

Normal Market

All orders which are of regular lot size or multiples thereof are traded in the Normal Market. For shares that are traded in the compulsory dematerialised mode the market lot of these shares is one. Normal market consists of various book types wherein orders are segregated as Regular lot orders, Special Term orders, Negotiated Trade Orders and Stop Loss orders depending on their order attributes.

Odd Lot Market

All orders whose order size is less than the regular lot size are traded in the odd-lot market. An order is called an odd lot order if the order size is less than regular lot size. These orders do not have any special terms attributes attached to them. In an odd-lot market, both the price and quantity of both the orders (buy and sell) should exactly match for the trade to take place. Currently the odd lot market facility is used for the Limited Physical Market as per the SEBI directives.

Auction Market

In the Auction Market, auctions are initiated by the Exchange on behalf of trading members for settlement related reasons. There are 3 participants in this market.

  • Initiator - the party who initiates the auction process is called an initiator
  • Competitor - the party who enters orders on the same side as of the initiator
  • Solicitor - the party who enters orders on the opposite side as of the initiator

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.

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.

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.

The best buy order is matched with the best sell order. An order may match partially with another order resulting in multiple trades. For order matching, the best buy order is the one with the highest price and the best sell order is the one with the lowest price. This is because the system views all buy orders available from the point of view of a seller and all sell orders from the point of view of the buyers in the market. So, of all buy orders available in the market at any point of time, a seller would obviously like to sell at the highest possible buy price that is offered. Hence, the best buy order is the order with the highest price and the best sell order is the order with the lowest price.

Members can proactively enter orders in the system, which will be displayed in the system till the full quantity is matched by one or more of counter-orders and result into trade(s) or is cancelled by the member. Alternatively, members may be reactive and put in orders that match with existing orders in the system. Orders lying unmatched in the system are 'passive' orders and orders that come in to match the existing orders are called 'active' orders. Orders are always matched at the passive order price. This ensures that the earlier orders get priority over the orders that come in later.

A Trading Member can enter various types of orders depending upon his/her requirements. These conditions are broadly classified into three categories: time related conditions, price-related conditions and quantity related conditions.

Time Conditions

DAY - A Day order, as the name suggests, is an order which is valid for the day on which it is entered. If the order is not matched during the day, the order gets cancelled automatically at the end of the trading day.

GTC - A Good Till Cancelled (GTC) order is an order that remains in the system until it is cancelled by the Trading Member. It will therefore be able to span trading days if it does not get matched. The maximum number of days a GTC order can remain in the system is notified by the Exchange from time to time.

GTD - A Good Till Days/Date (GTD) order allows the Trading Member to specify the days/date up to which the order should stay in the system. At the end of this period the order will get flushed from the system. Each day/date counted is a calendar day and inclusive of holidays. The days/date counted are inclusive of the day/date on which the order is placed. The maximum number of days a GTD order can remain in the system is notified by the Exchange from time to time.

IOC - An Immediate or Cancel (IOC) order allows a Trading Member to buy or sell a security as soon as the order is released into the market, failing which the order will be removed from the market. Partial match is possible for the order, and the unmatched portion of the order is cancelled immediately.

Note: Currently, GTC and GTD orders are not available on the system as per SEBI directives.

Price Conditions

Limit Price/Order – An order that allows the price to be specified while entering the order into the system.

Market Price/Order – An order to buy or sell securities at the best price obtainable at the time of entering the order.

Stop Loss (SL) Price/Order – The one that allows the Trading Member to place an order which gets activated only when the market price of the relevant security reaches or crosses a threshold price. Until then the order does not enter the market.

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. 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.

E.g. If for stop loss buy order, the trigger is 93.00, the limit price is 95.00 and the market (last traded) price is 90.00, then this order is released into the system once the market price reaches or exceeds 93.00. This order is added to the regular lot book with time of triggering as the time stamp, as a limit order of 95.00

Quantity Conditions

Disclosed Quantity (DQ)- An order with a DQ condition allows the Trading Member to disclose only a part of the order quantity to the market. For example, an order of 1000 with a disclosed quantity condition of 200 will mean that 200 is displayed to the market at a time. After this is traded, another 200 is automatically released and so on till the full order is executed. The Exchange may set a minimum disclosed quantity criteria from time to time.

MF - Minimum Fill (MF) orders allow the Trading Member to specify the minimum quantity by which an order should be filled. For example, an order of 1000 units with minimum fill 200 will require that each trade be for at least 200 units. In other words there will be a maximum of 5 trades of 200 each or a single trade of 1000. The Exchange may lay down norms of MF from time to time.

AON - All or None orders allow a Trading Member to impose the condition that only the full order should be matched against. This may be by way of multiple trades. If the full order is not matched it will stay in the books till matched or cancelled.

Note: Currently, AON and MF orders are not available on the system as per SEBI directives.

Updated on: 30/09/2019 12:00
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