What is a limit order?
Lesson 43 · practical guide
A limit order buys or sells only at a specified price or better. It controls price but not execution. A market order prioritises execution but can fill unexpectedly in a fast or thin market.
What you will learn
Use limit orders to control price, while accepting that execution is not guaranteed.
Key terms
- Limit order — an order to buy or sell only at a chosen price or better.
- Fill — an executed part or all of an order.
- Time in force — how long an order remains active.
Follow these steps
- Choose the limit from your plan, not from a random number on the screen.
- Check size, spread, tick size, minimum order and time-in-force settings.
- Know what happens if the order is partially filled or expires.
- Never assume a limit order protects against a gap after execution or against the asset losing value.
Practical advice
A buy limit can prevent paying above your chosen price, but it can also remain unfilled while the market moves away. Execution control and market risk are different problems.
Long-form explainer
The full guide
Read this lesson as a chapter: understand the mechanism, test the assumptions and apply the idea with a clear risk limit.
A limit order controls price, not execution
A limit order buys or sells only at the chosen price or better. This can protect you from accepting a fast, unfavourable quote, but it also means the order may fill partly or not at all. The order's time in force determines how long it remains active, and market conditions can change while it waits.
A visible limit price is not necessarily a fair value. The order book can be thin, cancelled or moved by other participants. The fill may be partial, and fees can differ depending on whether your order adds or removes liquidity. Read the venue's exact rules before relying on a label.
Use the order as part of the plan
Decide the maximum acceptable price, the order size, the time limit and what you will do if the order does not fill. Avoid chasing the market by repeatedly moving the limit without changing the thesis. For larger orders, consider how each portion may affect price and whether the order can be observed.
After execution, compare the intended price with the average fill, spread, fees and slippage. This record shows whether your order method helped or merely delayed the decision. Good execution is measured against the plan and liquidity available at the time.
What usually goes wrong
The first mistake is assuming a limit order will be filled. It controls price, not execution, and a buy limit placed below the market can sit unfilled while the price moves away permanently. The second error is the opposite: using market orders for everything because they always execute. In a thin book, particularly outside main trading hours or in a volatile moment, the fill can be far from the price displayed, and that difference is a real cost even though no fee line shows it.
People also leave resting orders they have forgotten about. An order placed weeks ago can execute after the reasoning behind it has stopped being true, which is how positions appear that nobody intended to hold. A further mistake is placing orders at obvious round numbers where everyone else places them, and being filled only when the market is moving through that level decisively. The final failure is ignoring order types that would fit better: a stop-limit or a post-only order exists precisely for the situation where price control and execution matter differently.
How it works
A limit buy can remain unfilled or partially fill. Check time-in-force, post-only rules and whether it persists after a session. A stale order can execute after the original reason is gone, so cancel orders that no longer fit.
A limit price does not remove asset risk: negative news can arrive immediately after the fill. Execution is always a trade-off between price control and certainty.
Worked example
Numbers make an idea concrete. Here is a small, illustrative one — not a forecast.
With a €20.10 sell price and €19.90 buy price, a €19.90 limit buy controls the maximum but may not fill; a market buy may fill at €20.10 or worse.
Before you act
Run through these questions before you commit any money or make a decision based on this lesson:
- Do I value price control over speed?
- What about gaps or partial fills?
- When does the order expire?
- Will the reason still exist later?
Practice this lesson
Reading is a start; doing the exercise is what makes the idea stick.
Use a simulated order book for market, limit and stop orders. Record spread, fill status, execution and new risks.
Further reading
Educational content only: This guide is not personal financial, legal or tax advice. Markets involve risk, including the possible loss of capital. Verify current rules, fees and product availability in your country.