The **IS (Implementation Shortfall) trajectory** is designed to **minimize the difference between the arrival price** (the price at order submission) **and the average execution price**. It dynamically **adjusts the execution schedule** to balance **market impact and timing risk**, making it particularly useful in **volatile or illiquid markets** where slippage is a concern.
#### **How Implementation Shortfall Works**
* Traders set an **aggressive execution profile**, **front-loading** a larger portion of the order to reduce **timing risk**.
* The engine **opportunistically places limit orders** to optimize costs but will **use market orders when necessary** to maintain execution speed.
* The trajectory follows a **VWAP (Volume Weighted Average Price) approach** with [**Alpha Tilt**](/creating-and-submitting-orders/advanced-settings/alpha-tilt.md) **set to 1**, ensuring **faster initial execution** while balancing cost efficiency.
#### **When to Use Implementation Shortfall**
* **Volatile Market Conditions** – Ideal for **reducing slippage** when price movements are unpredictable.
* **Urgent Trades** – Best for scenarios where **immediate execution** is prioritized over cost.
* **Illiquid Markets** – Helps traders **navigate limited liquidity** while minimizing timing risk.
#### **Implementation Shortfall Limitations**
* **Higher Market Impact** – The **aggressive front-loading** increases the likelihood of influencing market prices.
* **Potentially Higher Costs** – Frequent use of **market orders** may result in **higher taker fees**.
* **Less Suitable for Passive Strategies** – Not ideal if the goal is to **minimize visibility** and maintain a **low-profile market presence**.
This trajectory is best suited for traders who **need fast execution** in **volatile or illiquid markets**, ensuring **reduced slippage while managing execution costs**.
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