> For the complete documentation index, see [llms.txt](https://elysia.gitbook.io/elysia-perps/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://elysia.gitbook.io/elysia-perps/trading/order-types.md).

# Order Types

All orders go onto the same **central limit order book**, where they match by price and then time. Elysia Perps offers limit and market orders, plus fill-or-kill and reduce-only variants.

## Limit orders

A **limit order** sets the price you're willing to trade at. The portion that can fill immediately does so as a **taker**; any remainder rests on the order book as a **maker** order until it fills or you cancel it. (Limit orders are *good-till-cancel*: they stay live until filled or cancelled.)

* Buy limit: fills at your price **or better** (lower).
* Sell limit: fills at your price **or better** (higher).

### Price improvement

If your limit price is better than the best available price on the other side, you fill at the **better** price, not your limit:

* A buy limit at $96,000 against a best ask of $95,100 fills at **$95,100**, so you pay less than your limit.
* A sell limit at $94,000 against a best bid of $94,900 fills at **$94,900**, so you receive more than your limit.

## Market orders

A **market order** fills immediately against the best available prices and **cancels any unfilled remainder**. It never rests on the book. (Market orders are *immediate-or-cancel*.)

* A market order is always a **taker**.
* The price you set acts as a **slippage limit**: the worst price you'll accept. The order fills through the book up to that limit and cancels the rest, so a thin book can leave a market order partially filled.

## Fill-or-Kill (FOK)

A **fill-or-kill** order fills **completely and immediately, or is rejected entirely**, with no partial fills. Use it when you want all-or-nothing execution.

## Reduce-Only

A **reduce-only** order can only **shrink or close an existing position**. It can never open or increase one. It's the safe way to take profit or cut a position without accidentally flipping to the other side.

A reduce-only order is accepted only if:

1. you already have a position in that market,
2. the order is on the **opposite** side of that position, and
3. its size is **not larger** than the position.

Because it only reduces risk, a reduce-only order locks **no additional margin**. It is also **exempt from the $1 minimum-notional floor** that normal orders must meet. It only has to clear the market's minimum order size (0.00001 BTC on BTC-PERP-EL). This lets you close out a small remaining position even when its notional is under $1. See [Order size and price limits](/elysia-perps/trading/markets.md#order-size-and-price-limits).

## Maker vs. taker

|      | Taker                                                      | Maker                                  |
| ---- | ---------------------------------------------------------- | -------------------------------------- |
| What | Removes liquidity (market orders, instantly-filled limits) | Adds liquidity (a resting limit order) |
| Fee  | 0.05%                                                      | 0.02%                                  |

Fees are covered in **Mechanics → Fees**.

## Self-trade prevention

If your own order would match against another of *your* resting orders, the protocol cancels **both sides** of the overlap instead of trading. No trade, no fee, and no position change results from a self-match. It simply prevents you from trading with yourself.

## Where to go next

* How leverage and margin work: [Margin & Leverage](/elysia-perps/trading/margin-and-leverage.md).
* How a position evolves as orders fill: [Positions](/elysia-perps/trading/positions.md).


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