# Limit Order

Buy at a chosen maximum price or sell at a chosen minimum price.

A limit order trades only at your chosen price or better, even if that means waiting or not filling.

## What it does

A **limit order** gives you control over the worst price the order may accept. A Limit buy can execute at its limit price or lower, while a Limit sell can execute at its limit price or higher.

If eligible liquidity is not available, the order can remain open, fill partially, or end without a fill according to its [time-in-force instruction](https://testnet.polyester.com/docs/user-docs/trade/order-types/time-in-force-and-post-only).

## How it works

| Side | Price boundary                                    | Example                                                   |
| ---- | ------------------------------------------------- | --------------------------------------------------------- |
| Buy  | The order cannot pay more than the limit price    | A buy at 99,000 USDT can fill at 99,000 USDT or lower     |
| Sell | The order cannot accept less than the limit price | A sell at 101,000 USDT can fill at 101,000 USDT or higher |

A Limit order can rest in the Order Book, but it can also execute immediately when its price crosses available liquidity. Add [post-only](https://testnet.polyester.com/docs/user-docs/trade/order-types/time-in-force-and-post-only) when it must add liquidity instead of executing immediately as a taker.

> **A limit price does not guarantee a fill**
>
> The market may never reach your price, or only part of the requested quantity may become available there.

## When to use it

- **Use it when your price boundary matters most.** Choose a Limit order when you will buy only at or below a maximum price, or sell only at or above a minimum price.
- **Avoid it when you need to trade immediately.** Choose a Market order when attempting execution now matters more than waiting for one price or better.

Choose the limit price, time-in-force, and post-only setting based on whether the order may wait, take liquidity immediately, or must remain maker-only.

## Example

Let's say Bitcoin is currently trading at **100,000 USDT**. You want to buy **0.01 BTC**, but only if the price falls to **99,000 USDT or lower**. Because that maximum price matters more to you than buying immediately, you choose a Limit order.

1. You submit a Limit buy for 0.01 BTC at 99,000 USDT.
2. The best available ask is still above 99,000 USDT, so the order waits in the Order Book.
3. Bitcoin falls and 0.006 BTC becomes available at 99,000 USDT, partially filling the order.
4. The remaining 0.004 BTC later fills at 98,950 USDT, which is better than your limit price.

**Result:** You buy 0.01 BTC for 989.80 USDT before fees, at an average price of 98,980 USDT. The order never pays more than 99,000 USDT per BTC.

*These are example prices and available quantities. If the market never reaches the limit, the order may remain open or end without filling.*

## What to watch

- A Limit order is not guaranteed to fill.
- Partial fills can leave quantity open in the Order Book.
- A crossing Limit order can execute immediately as a taker.
- Time-in-force determines what happens to unfilled quantity.
- Use a [Market Order](https://testnet.polyester.com/docs/user-docs/trade/order-types/market-order) when trading immediately matters more than one fixed price.