Education

Why Your Fill Price Can Differ From the Price on Screen

By Walid Mograbi · 2026-04-17 · 2 min read

The quote on screen is a moment in time, not a promise. Your final fill depends on market speed, liquidity, spread, and the way your order reaches the market.

Why this matters

Many new traders believe the price they see on the screen is the price they will receive. In real markets, that number is only a quote at a moment in time. The final fill can differ because the order still has to travel, match, and consume whatever liquidity is available when it arrives.

What slippage actually means

Slippage is the gap between the price you expected and the price you actually received. It becomes more visible when markets move quickly, when liquidity is thinner, or when the order size is larger than the resting liquidity near the quote. This is not always a hidden fee. Often it is simply how price discovery works in a live market.

Practical example

Imagine you see a price near 100 and press buy during a fast move. If the best available sell orders are lifted before your order reaches the market, your execution may happen at 100.20 or 100.40 instead. The screen was not necessarily wrong. It was simply no longer current by the time your order was matched.

Common mistakes to avoid

Treating the last visible price like a guarantee.
Ignoring liquidity and spread when placing a larger order.
Assuming fast movement means easy execution.
Confusing slippage with proof that the market is manipulated every time.

Quick checklist

Ask what type of order you are using.
Check whether the market is moving unusually fast.
Remember that larger size can move through multiple price levels.
Separate what you saw on screen from what the market could actually fill.

Key takeaway

The screen shows an opportunity snapshot, not a promise. A trader who understands liquidity and execution quality will read the market more realistically than a trader who judges everything from the last printed price.