> For the complete documentation index, see [llms.txt](https://docs.yellow.pro/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.yellow.pro/perpetual-trading/contract-specifications.md).

# Contract Specifications

Every perpetual order is checked against the contract's rules **before it's accepted**. An order that breaks any rule is **not created** — the platform blocks it at submission, so it never enters the order book or your Order History. **If you're unable to place an order, one of the rules below is the most likely reason.** This page lists the rules and the current values for each perpetual contract.

## Order Validation Rules

| Rule                   | What it means                                                                       | You can't place the order if…                                    |
| ---------------------- | ----------------------------------------------------------------------------------- | ---------------------------------------------------------------- |
| **Tick size**          | The smallest allowed price increment. Your price must be an exact multiple of it.   | Price is not a multiple of the tick size.                        |
| **Step size**          | The smallest allowed amount increment. Your amount must be an exact multiple of it. | Amount is not a multiple of the step size.                       |
| **Minimum order size** | The smallest amount (in the base asset) you can trade.                              | Amount is below the minimum.                                     |
| **Maximum order size** | The largest amount (in the base asset) per order.                                   | Amount is above the maximum.                                     |
| **Minimum notional**   | The smallest order *value* (price × amount, in USDT).                               | Order value is below the minimum notional.                       |
| **Price band**         | A limit price must stay within a range around the reference (mark) price.           | Price is below **50%** or above **150%** of the reference price. |
| **Maximum leverage**   | The highest leverage allowed on the contract.                                       | Selected leverage exceeds the maximum.                           |
| **Available margin**   | You must have enough free margin to open or increase the position.                  | Available margin is insufficient.                                |

{% hint style="info" %}
The **price band** is why a limit order placed far from the current price can be blocked even when its price is otherwise valid. It prevents fat-finger orders and trades at unrealistic prices.
{% endhint %}

## Contract Specifications

| Contract         | Min order | Max order     | Step size | Tick size | Price band              | Min notional | Max leverage | Maintenance margin |
| ---------------- | --------- | ------------- | --------- | --------- | ----------------------- | ------------ | ------------ | ------------------ |
| **BTCUSDT-PERP** | 0.001 BTC | 1,000,000 BTC | 0.001     | 0.1       | 50% – 150% of reference | 1 USDT       | 100×         | 0.5%               |
| **ETHUSDT-PERP** | 0.001 ETH | 1,000,000 ETH | 0.001     | 0.01      | 50% – 150% of reference | 1 USDT       | 100×         | 0.5%               |

The **maintenance margin rate (MMR)** is the fraction of position notional you must keep to avoid liquidation. See [Margin & Leverage](/perpetual-trading/margin-and-leverage.md) and [Liquidation & Mark Price](/perpetual-trading/risk-and-liquidation/liquidation-and-mark-price.md) for how leverage and maintenance margin affect your positions.

## Market-order slippage tolerance

A market order opens immediately at the best available price, so the fill price can differ from the mark price shown at submission. To stay funded if it fills at a worse price, a market order reserves about **5% extra initial margin** on top of the normal requirement.

## Worked Examples

<details>

<summary>Price not aligned to tick size</summary>

You place a limit order on **BTCUSDT-PERP** at **60,000.05**. The tick size is **0.1**, so the price must end at a multiple of 0.1 (e.g. `60,000.0` or `60,000.1`). You won't be able to place it — round your price to the tick size and try again.

</details>

<details>

<summary>Limit price outside the price band</summary>

With BTC trading around **60,000**, you place a limit buy at **20,000** — below **50%** of the reference price (30,000). The order falls outside the price band, so it's blocked. Place the order within the allowed range around the current price.

</details>

<details>

<summary>Amount below the minimum / not aligned to step size</summary>

You try to open a **0.0005 BTC** position on BTCUSDT-PERP. The minimum order size is **0.001** and the step size is **0.001**, so `0.0005` is both too small and not a valid increment. Use `0.001`, `0.002`, and so on.

</details>

## Related Articles

* [Margin & Leverage](/perpetual-trading/margin-and-leverage.md)
* [Liquidation & Mark Price](/perpetual-trading/risk-and-liquidation/liquidation-and-mark-price.md)
* [FAQ](/perpetual-trading/faq.md)