Iceberg Order
An Iceberg Order is a large order on an exchange that is divided into a smaller displayed quantity visible in the public order book and a larger hidden reserve quantity that is automatically refreshed each time the displayed portion is fully executed, concealing the full extent of the participant's interest.
The iceberg metaphor is apt: just as only a fraction of an iceberg is visible above the water surface, an iceberg order reveals only a portion of its total size in the publicly displayed order book. This concealment is deliberate — large participants seeking to accumulate or distribute significant positions know that revealing their full size would move the market against them, as other traders would adjust their prices in anticipation of the large transaction.
The mechanics on NSE are straightforward. When placing an order, a participant specifies a Disclosed Quantity (DQ) that is less than the total order quantity. The exchange's system places only the DQ in the visible order book. As the displayed portion is executed, the system automatically replenishes it from the hidden reserve until the entire order is filled or the participant cancels.
From a market microstructure perspective, iceberg orders create a gap between displayed liquidity and actual liquidity. A market participant observing five-thousand shares offered at a particular price may be unaware that a ten-lakh-share sell iceberg is resting there, repeatedly refreshing. The order book appears to show thin supply, but every attempt to exhaust that supply results in automatic replenishment.
Order flow analysts watch for 'absorption' patterns that may indicate a hidden iceberg: repeated attempts by buyers to push price above a level, each time met by fresh supply at the same price despite the visible offer appearing small, suggest an iceberg seller is absorbing demand. Similarly, price that refuses to decline below a level despite visible bid depth appearing modest may indicate an iceberg buyer.
NSE rules specify a minimum Disclosed Quantity — typically at least 10 percent of the total order size or a minimum absolute quantity — to prevent the disclosed portion from being set so small that the order becomes effectively invisible. BSE has analogous requirements. Institutional brokers often advise clients on optimal iceberg sizing: too small a disclosed quantity triggers frequent book refreshes and may attract attention; too large a disclosed quantity defeats the concealment purpose.
Iceberg orders are widely used by mutual funds, insurance companies, and FPIs executing large equity trades on NSE to minimise market impact during portfolio construction and rebalancing.