Slippage

What Is Slippage?

Slippage is the difference between the price an investor expected when placing a trade and the actual price received when the order was executed. It happens when the quoted or last-seen price changes before the order is filled, or when there is not enough depth at the expected price to complete the order. Slippage can work for or against the investor, but most discussions focus on negative slippage because that is the form that raises trading cost.

Slippage is a real trading friction, not just a charting inconvenience. It is one of the main reasons investors can see an acceptable quoted price on screen and still receive a worse actual fill.

Key Takeaways

• Slippage is the gap between the expected trade price and the execution price.
• It is more common in fast-moving or less liquid markets.
• Market orders are especially exposed because they prioritize execution over price control.
• Slippage is different from a bid-ask spread, although both affect trading cost.
• Execution quality and best execution help determine how much slippage investors face in practice.

How Slippage Happens

Trade execution is usually quick, but it is not perfectly instantaneous. By the time an order reaches the market, the quoted price may have changed. Even if the quote has not moved, the visible price may have been available only for a limited number of shares. If the order is larger than that available size, the remaining portion may execute at worse prices.

This is why slippage tends to become more noticeable during sharp volatility, around major news releases, or in securities with weak liquidity. It can also affect orders placed outside normal market hours, when price discovery is often less orderly.

Positive Slippage and Negative Slippage

Negative slippage means the investor receives a worse price than expected. A buyer pays more than intended, or a seller receives less than intended. Positive slippage means the opposite: the order is filled at a better price than expected. Both are possible because the market is still moving while the trade is being processed.

In practice, investors worry more about negative slippage because it behaves like an extra hidden trading cost. It can quietly reduce return even when the visible commission is low or zero.

Slippage Versus the Bid-Ask Spread

The spread is a known market cost at a point in time. Slippage is the additional difference that can arise when the order is actually executed. Both contribute to transaction costs, but slippage is the more variable and less predictable part.

How Order Type Changes Slippage

Order type changes how exposed the investor is to slippage. A market order is designed to get the trade done, so it accepts whatever price is available when the order reaches the market. A limit order can reduce unwanted price drift by refusing to trade beyond a specified threshold, but it introduces the possibility that the order will not fill. A stop order can also experience slippage because once it triggers, it becomes a market order.

This is why slippage cannot be evaluated in isolation. It sits inside the broader tradeoff between execution certainty and price certainty.

How Investors Try To Reduce Slippage

Investors often try to reduce slippage by trading more liquid securities, placing orders during normal market hours, avoiding unusual volatility when possible, and using order types that fit the trading goal. Breaking a very large order into smaller pieces can also help in some situations because it reduces pressure on the available quote size.

Broker routing quality matters as well. The broker's handling of order flow, access to execution venues, and overall execution process can influence whether the investor receives a price close to the quoted market or something materially worse.

The Bottom Line

Slippage is the difference between the expected trade price and the price actually received when the order is executed. It matters because it can quietly increase trading cost, especially in volatile or illiquid markets and especially when investors use order types that prioritize speed over price control.