> ## Documentation Index
> Fetch the complete documentation index at: https://developer.buildmarkets.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Dollar Amount & Fractional Orders

> How the FIX Gateway supports dollar-amount notional orders and fractional share quantities, both as Market orders only.

## Overview

The Buildmarkets FIX Gateway enables two specialized order types for more flexible trading.

### Dollar Amount Orders

These orders let you specify a dollar value instead of share quantity. Key requirements: Tag 38 (OrderQty) must be `0`; Tag 40 (OrdType) must be `1` (Market only); Tag 152 (CashOrderQty) contains the dollar amount. "When `OrderQty=0` and `CashOrderQty` is set, the gateway converts the dollar amount into the appropriate share" quantity using current market pricing. A $100 order on a $228 stock would execute as approximately 0.4386 shares.

**Example message:**

```
8=FIX.4.4|35=D|49=CLIENT1|56=BROKERX|11=ORD12345|55=AAPL|54=1|38=0|40=1|60=20250430-14:22:30.000|152=100|10=123|
```

### Fractional Orders

These accept decimal share quantities in Tag 38 (OrderQty), such as `0.5` for half a share. Market order type (`OrdType=1`) is required.

**Example message:**

```
8=FIX.4.4|35=D|49=CLIENT1|56=BROKERX|11=ORD12345|55=AAPL|54=1|38=0.5|40=1|60=20250430-14:22:30.000|10=123|
```

## Constraints

Both order types must be Market orders only — Limit, Stop, and Stop Limit orders are not supported. The REST API offers equivalent functionality through the `OrderQuantity` parameter.