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Market Intelligence › Basic Terminologies
Certainty of fill versus certainty of price — you never get both together
Published by The Retail Trader · JUL 22, 2026 · Order Flow
Every order picks one of two things: either a guaranteed price, or a guaranteed fill. You never get both together, and most bad fills come from not understanding this.
A market order says: fill it at whatever the best available price is. The fill is almost certain, but the price you get can be one you never expected.
A limit order says: fill only at this price or better. The price is certain, but the order may sit unfilled or may not fill completely.
The choice depends on liquidity, not habit:
• In a very liquid stock and a normal market, the cost of a market order is small.
• In an illiquid stock, a market order can be the most expensive decision — the spread itself is wide.
• A market order slips the most in the first minute after the open and right after big news.
• In an emergency exit, certainty of fill becomes more important — there you should not be stubborn with a limit.
Look at the depth window once before placing an order. If the gap between the best bid and the best ask is itself a large part of your expected profit, the maths of that trade is already broken before you choose the order type.
This article is for education only — it is not a buy or sell recommendation, makes no claim of guaranteed returns, and is not advisory. Rules, rates and mechanics are changed from time to time by the exchanges, SEBI and RBI, so verify every number yourself with your broker or an official source.