What is slippage?

If the price at which your order was executed does not match the price that was requested, slippage occurs. This occurs when the market moves to the detriment of your trade and the price originally entered is no longer available after the order has been processed by the broker. Slippage can occur at any time and has two main causes. The first cause is high volatility in the market. The second cause is gapping in the market. This occurs when the market moves up or down rapidly, with little or no intermediate trading.