A limit order is an instruction to buy or sell only at a specific price or better. For a buy, you set the maximum you are willing to pay. For a sell, you set the minimum you are willing to accept. The order will not execute at a worse price.
This contrasts with a market order, which aims to execute immediately at the best available prices, wherever they are. With a limit you control price. With a market order you prioritise speed.
What happens in the order book
Exchanges hold a live queue of bids and offers called the order book. Buy limits sit on the bid side, sell limits sit on the ask side. Orders are matched using price-time priority, which simply means better prices are matched first, and within the same price, the orders that arrived earlier go ahead of later ones.
If you place a buy limit below the current ask, it will rest in the book waiting for sellers to meet your price. If you place a sell limit above the current bid, it will rest waiting for buyers. If your limit crosses the spread, it becomes a marketable limit order and can trade straight away. For example, if the best ask is 100.20 and you submit a buy limit at 100.50, you will typically buy immediately at the best prices up to 100.50. You might even receive price improvement if better prices are available than your limit.
Execution can be full or partial. If there is not enough volume at acceptable prices, you might get part of your order executed now and leave the remainder resting. Each executed piece is recorded as a fill with its own size and price.
Buy and sell examples you will recognise
Imagine a share quoting 100.00 bid and 100.20 ask.
- Buy limit below the market: You set a buy limit at 99.80. Nothing happens until sellers appear at 99.80 or better. If the price dips to 99.80, you may get filled depending on queue position and available size.
- Sell limit above the market: You set a sell limit at 100.80. It will rest until buyers are willing to pay 100.80 or higher. If the price rises, you can be filled at 100.80 or better.
- Marketable buy limit: You place a buy limit at 100.50 while the ask is 100.20. The order sweeps available offers between 100.20 and 100.50. If only half your size is available up to 100.50, the filled half trades now and the rest sits as a bid at 100.50.
The key idea is right in the name. Your limit sets the worst price you will accept, and the system will try to do better when possible.
Time-in-force options and order qualifiers
A limit order also needs instructions for how long it should stay active and how it should behave. Common time-in-force choices include:
- Day. Active for the trading day, then expires if not filled.
- GTC (good till cancelled). Stays open until you cancel it or until a broker-defined cut-off. Exact expiry rules can vary by provider.
- IOC (immediate or cancel). Fill whatever can execute now, cancel the rest.
- FOK (fill or kill). Fill the entire order now at your limit or better, or cancel it entirely.
Some venues also offer qualifiers such as post only, which ensures your order adds liquidity rather than taking it. Names and precise behaviour differ by broker and exchange, so check the platform’s definitions before you rely on a setting.
Partial fills, queues and why limits do not fill
Limit orders fail to execute for straightforward reasons: the market never trades at your price, there is not enough volume when it does, or you are too far back in the time queue. Even if the price touches your level, a rush of earlier orders at the same price can be filled ahead of you, leaving your order untouched.
Order routing also matters. In markets with multiple venues, your broker decides where to send your order. Different venues may display different liquidity, hidden orders or auction periods. Providers may also internalise orders or use smart routers. All of this can affect how quickly a resting limit gets attention, and the behaviour can vary by provider.
Halts, auctions, price limits and odd-lot rules can further affect execution. In short, the price print alone does not guarantee a fill. Volume and queue position do the heavy lifting.
Limits vs market and stop orders
A market order is for urgency. You accept the prevailing prices to get the trade done now, which exposes you to slippage if the book is thin or moving fast. A limit order controls that slippage by setting a cap for buys or a floor for sells, but you may miss the trade if the market moves away.
Stops are about triggering. A stop market order becomes a market order once the stop level is reached. A stop-limit order becomes a limit order once triggered. The trade-off with stop-limit is similar to a regular limit: you remove the risk of an unexpectedly bad fill but you introduce the risk of no execution at all, especially through gaps.
Many traders use a mix. They might enter with a resting buy limit near perceived support, then use a stop market to exit if the thesis fails. Others use marketable limit orders that cross the spread to grab liquidity while still capping the worst acceptable price.
Costs, slippage and when limits make sense
Limit orders are popular because they give price control. They can help avoid overpaying in fast markets or in thinly traded shares. They also let you stage into positions by placing several orders at different prices rather than one large market order that could move the price.
On some exchanges, adding liquidity can qualify for lower fees than taking liquidity, though fee schedules vary widely. In crypto and certain equity venues, maker-taker models reward resting orders and charge for marketable ones. Your actual costs depend on the venue, instrument and your broker’s pricing.
There is a risk side. If a limit buy sits well below the market, you might never get in. If a sell limit sits well above, you might watch a rally peak just below your level. For exits, a strict limit can fail to execute during a sharp gap, leaving you with continued exposure when you wanted out. Choosing the right level and time-in-force is therefore central to using limits well.
Typical use cases include staging entries around support or resistance, trading news with a price cap, placing iceberg or post-only orders to avoid taking, and working larger orders over time. In very liquid instruments, the trade-off narrows because spreads are tight and depth is deep. In illiquid names or outside regular hours, the protection from a limit often matters more.
One practical tip. If you want your order to rest and not execute immediately, set buy limits at or below the current bid and sell limits at or above the current ask. If you place a buy limit above the best ask, or a sell limit below the best bid, you are effectively submitting a marketable limit and it can execute right away up to your price.
Limit orders work across stocks, ETFs, futures and many crypto markets, but the fine print differs by provider and venue. Always check how your platform handles time-in-force, routing, auctions and partial fills before relying on a specific behaviour.