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Limit Orders

A limit order is an instruction to buy or sell only at a specified price or better, giving you full control of the price you accept but no guarantee that the order will ever be filled.

Quick answer: A limit order is an instruction to buy or sell only at a specified price or better, giving you full control of the price you accept but no guarantee that the order will ever be filled.

In simple words

A limit order says 'trade me only at this price or better, otherwise wait'. If you place a buy limit below the current price it rests in the order book until a seller comes to your price. You control exactly what you pay, but you might sit unfilled while the market walks away from you.

Purpose

Limit orders exist so a trader can control execution price, earn rather than pay the spread by providing liquidity, and place resting orders that work while unattended — the backbone of passive and market-making style execution.

Visual explanation

Limit Orders

A passive buy limit resting below the touch versus a marketable limit that crosses to fill immediately.

Order Types on the Price LadderMarket — fills now at best priceLimit — only at set price or betterStop — becomes market once triggeredPrice →Sell Limit (above)Buy Stop (trigger)Market priceBuy Limit (below)

Professional explanation

Price certainty, fill uncertainty

A limit order flips the market order's trade-off. You state the worst price you will accept — a buy limit fills at your price or lower, a sell limit at your price or higher — so the price is certain. What is uncertain is whether it fills at all. If the market never trades at your limit, the order simply rests and then expires, and you have missed the move entirely. This is the central risk of passive execution: opportunity cost, not a bad fill.

Passive versus marketable limits

A limit order is passive (liquidity-adding) when it is priced away from the touch — a buy below the best bid or a sell above the best ask — so it rests in the book and waits. It is marketable (liquidity-taking) when priced at or through the touch — a buy at or above the best ask — so it crosses the spread and fills immediately, behaving almost like a market order but with a price cap. The same order type serves opposite purposes depending only on where you set the price.

Queue position and price-time priority

The NSE matches on strict price-time priority: better-priced orders trade first, and among orders at the same price the one entered earliest trades first. When you post a passive limit, you join the back of the queue at your price level. Your fill probability depends on your position in that queue — every order ahead of you must be filled or cancelled before yours trades. Modifying an order's price, and on most systems increasing its quantity, loses your time priority and sends you to the back of the queue, which is why serious passive traders avoid needless amendments.

Why passive orders can be picked off

Resting a limit order is effectively writing a free option to the rest of the market: you will be filled precisely when someone wants to trade against you, which is often when information has just moved against your side. This adverse selection means a naively posted buy limit tends to fill just as the price is about to fall further. Market makers manage this by quoting tight two-sided prices, skewing quotes with inventory, and pulling quotes when they detect toxic flow.

Immediate-or-cancel and validity

Limit orders carry a validity: DAY (rests until the close), IOC (immediate-or-cancel — fills what it can right now and cancels the rest), or GTT-style persistent triggers offered at the broker layer on the NSE. An IOC limit is a common execution primitive for algos that want to take only what is available at their price without leaving a resting footprint. Understanding validity is part of controlling whether your order behaves passively or aggressively.

Modelling limit fills in a backtest

Backtesting limit orders honestly is harder than market orders because a fill is conditional. A common conservative rule is to assume a buy limit fills only if the bar's low trades strictly below your limit (not merely touches it), acknowledging queue position by requiring the price to trade through you. Assuming every touched limit fills is a subtle look-ahead-style optimism that overstates passive strategies, since in reality being at a price does not guarantee your place in the queue cleared.

Market order vs Limit order

AspectMarket orderLimit order
Fill certaintyNear-guaranteedNot guaranteed
Price certaintyNoneGuaranteed at limit or better
Spread costPays the spreadCan earn the spread if passive
Liquidity roleTakes liquidityAdds liquidity when passive
Speed to fillImmediateImmediate if marketable, else waits
Main riskSlippage / bad fillMissing the trade entirely
Queue positionNot applicableMatters — price-time priority
Best used forUrgent exits, liquid namesControlled entries, providing liquidity

Practical example

Illustrative example (Indian market)

Nifty is trading with a best bid of 24,998 and best ask 25,002. You believe fair value is nearer 24,995, so you post a passive buy limit at 24,996 for one lot (75). Your order rests just below the touch and waits. If the market dips and a seller crosses down to 24,996, you fill at 24,996 — 2 points better than the mid and having paid no spread. But if Nifty rallies to 25,050 without ever printing 24,996, your order never fills and you have missed a 50-point move; your cost was zero rupees but a real opportunity. Had you instead priced the buy limit at 25,002 (a marketable limit), you would have filled immediately against the ask, capped at 25,002.

On the NSE, retail 'GTT' (Good Till Triggered) orders at brokers like Zerodha are a client-side wrapper: the limit order is only pushed to the exchange when a trigger condition is met, because the exchange itself does not natively hold multi-day resting orders for retail. This matters for algos — a GTT is not a true resting book order and will not hold queue priority the way a live DAY limit does.

Advantages

  • Full control of the execution price — you never pay worse than your limit
  • Can earn the spread and even a rebate-like edge by providing liquidity passively
  • Rests unattended, so it works signals while you are away
  • Marketable limits give near-market speed with a worst-price safety cap

Limitations

  • No guarantee of a fill — the market can move away and leave you flat
  • Passive orders suffer adverse selection: you fill when the move is against you
  • Queue position is fragile; modifying price or size costs your time priority
  • Opportunity cost of a missed trade is invisible on the contract note but very real
  • Partial fills can leave an awkward residual quantity to manage

Why it matters in practice

  • Passive limit execution is how strategies reduce or eliminate spread cost, materially improving net returns for high-turnover systems
  • Fill probability, not just price, becomes a first-class variable an execution engine must model

Common mistakes

  • Assuming a resting limit will fill because the price 'reached' it, ignoring the queue ahead of you
  • Repeatedly modifying a limit's price, which resets time priority and pushes you to the back of the queue each time
  • Setting a buy limit so far below the market that it never fills, then wondering why the signal was missed
  • Backtesting limits as filled whenever the bar merely touches the price, overstating passive-strategy returns
  • Forgetting a passive fill happens when the market is moving against you, and treating the fill price as a bargain
  • Confusing a broker GTT wrapper with a true exchange-resting limit that holds queue priority

Professional usage

Quantitative execution teams treat the passive-versus-aggressive choice as a continuous decision, not a binary one. They post passive limits to capture spread when urgency is low and the alpha is durable, then become marketable — crossing the spread — as a deadline approaches or the signal risks decaying. Sophisticated desks model fill probability as a function of queue position, spread and volatility, and route child orders accordingly. The governing idea is that a limit order is a bet on both price and time, and both sides of that bet must be priced.

Key takeaways

  • A limit order guarantees price but not a fill — the opposite trade-off to a market order.
  • Passive limits can earn the spread but suffer adverse selection and queue risk.
  • Price-time priority means your place in the queue, and needless amendments, decide your fill.
  • Model limit fills conservatively in backtests — require the price to trade through you, not just touch it.

Frequently asked questions

What is a limit order?
A limit order is an instruction to trade only at a specified price or better. A buy limit fills at your price or lower and a sell limit at your price or higher, so you control the price but accept that the order may never fill.
Why did my limit order not fill even though the price reached it?
Because being at a price is not the same as clearing the queue at that price. Orders match on price-time priority, so every order entered ahead of yours at that level must fill first; if the price only touched your level briefly, the depth there may never have reached you.
What is the difference between a passive and a marketable limit order?
A passive limit is priced away from the touch so it rests and adds liquidity, waiting to be filled. A marketable limit is priced at or through the touch so it crosses the spread and fills immediately, behaving like a market order but with a worst-price cap.
What is queue position and why does it matter?
Queue position is where your order sits among all orders at the same price, ordered by time of entry. It matters because orders ahead of you must be filled or cancelled before yours trades, so a better queue position directly raises your probability of getting filled.
Does modifying a limit order lose my place in the queue?
Changing the price always resets your time priority and sends you to the back of the queue at the new level. On most exchanges increasing quantity also loses priority, while reducing quantity usually keeps it, which is why disciplined passive traders modify as little as possible.
Can a limit order earn the spread?
Yes. If you post a passive buy limit at the bid and sell at the ask, and both fill, you capture the bid-ask spread instead of paying it. This is the core of market-making style execution, though it carries adverse-selection risk.
What is adverse selection on a resting limit order?
It is the tendency for your passive order to fill precisely when the market is about to move against you, because informed traders trade against stale quotes. In effect a resting limit is a free option you have written to the rest of the market.
What is an IOC limit order?
An Immediate-Or-Cancel limit fills as much as it can at your price right now and cancels any remainder instead of resting. Algorithms use it to take available liquidity at a chosen price without leaving a visible resting order in the book.
Is a limit order guaranteed to fill?
No. A limit order guarantees the price but not the fill. If the market never trades at your limit, or the queue ahead of you is never cleared, the order simply expires unfilled and you miss the trade.
When should I use a limit order instead of a market order?
Use a limit order when controlling price matters and you can tolerate missing the trade — for patient entries, illiquid instruments where a market order would fill badly, or when you want to provide liquidity and capture the spread.
How do I backtest limit orders realistically?
A conservative rule is to fill a buy limit only when the bar's low trades strictly below your price, and a sell limit only when the high trades strictly above, so the price must move through you. Filling on a mere touch overstates how often passive orders actually execute.
What is a GTT order on the NSE and is it a real resting limit?
A Good Till Triggered order is a broker-side wrapper that pushes a limit order to the exchange only when a trigger price is hit. It is not a native multi-day exchange order, so it does not hold live queue priority the way a DAY limit that is already resting in the book does.
Can a limit order fill partially?
Yes. If only part of the quantity at your price is available, the order can fill partially and rest for the remainder (or cancel it, if IOC). Managing that residual quantity is a normal part of limit-order execution.
Why might a passive limit be a bad idea for a fast signal?
Because a signal whose edge decays quickly can evaporate while your passive order waits unfilled. If the cost of missing the trade exceeds the spread you hoped to save, a marketable limit or market order is the better choice.

Voice search & related questions

Natural-language questions people ask about Limit Orders.

What is a limit order in plain words?
It is an order to buy or sell only at your chosen price or better. You control the price, but the trade might never happen if the market does not come to you.
Why didn't my limit order fill?
The price may have touched your level but not cleared the queue ahead of you, or the market moved away before reaching you. A limit only fills when someone actually trades at your price with your order first in line.
What is the difference between a limit and a market order?
A limit order controls price but may not fill, while a market order fills now but at any price. One protects your price, the other protects your fill.
Can I make money from the spread with a limit order?
Yes, if you post passively and both your buy and sell fill, you earn the spread instead of paying it. But you take on the risk of filling when the market turns against you.
Should I keep changing my limit price to get filled?
Be careful — every price change sends you to the back of the queue and can hurt your fill chances. Chasing the market with constant edits often backfires.
When is a limit order better than a market order?
When price control matters more than certainty of filling, such as patient entries or thin instruments where a market order would fill badly.

Sources & references

    Last reviewed 11 July 2026. Educational content only — not investment advice. Markets and rules change; verify current conventions with SEBI, NSE/BSE and your broker.

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    Educational content only — not investment advice. Examples use illustrative numbers and simplified models. Algorithmic trading and derivatives involve substantial risk. See our Risk Disclosure and SEBI Disclaimer.