Why Does My Fill Price Differ From the Price on the Chart?

A price line on a chart is a record of the last trade. Somebody bought and somebody sold at that number. How long ago depends on the feed.

Your order has no interest in that trade. It meets the quotes standing in the market when it arrives: the ask if you are buying, the bid if you are selling.

Four reasons the numbers part

The spread. Every stock has a bid below and an ask above. The last trade can have happened at either one, or between them, so the chart price can sit a cent or several cents away from where you will actually transact. Sellers get the mirror image. A market sell meets the bid, which sits below the chart whenever the last print was at the ask.

The data. Some charts use delayed data, and some basic feeds draw on a limited set of venues. A delayed chart can be showing you a price the market left behind minutes earlier, and in a moving stock that alone explains a large gap between what you saw and what you got.

Aggregation. A one-minute candle closes on the last trade of that minute. It hides everything that happened inside it, including the brief lift in the ask that your market order happened to meet.

Time. Between your click and the execution, the quote can change. In a fast stock that interval is enough.

A spread worked through

None of those fills is an error. Each one is what a correctly executed market order looks like against a two-sided quote, and the chart, by design, shows none of that, because it only records completed trades and says nothing about the bids and offers that were waiting on either side when your order arrived.

The midpoint, 18.42 here, is a useful mental reference. It is rarely a price you can trade at with a market order.

Where price improvement comes from

The NBBO is the best bid and best offer across the US exchanges. Some fills land inside it. When that happens the execution report may label the difference as price improvement.

How much improvement you get, and how often, depends on how your order is routed. Retail orders at many brokers go to wholesalers, a practice tied to payment for order flow, and the improvement figures brokers publish are their own claims, which you can read but cannot easily verify from one fill.

How to check a fill

Open the execution report for the order. It should show the exact execution time, the fill price and, at many brokers, the quote at the time of execution.

Then look at time and sales for the same second. Find trades printed near your fill price. If your fill matches prices that were trading then, the order was filled at the market; if it sits well away from anything printed around that timestamp, ask your broker to explain it.

For larger orders, compare your average fill with the day’s VWAP. It gives you a rough benchmark of whether you paid more or less than the average share that traded, although it says little about a single small order.

One habit helps more than any of this. Look at the bid and the ask before you send an order, because that pair, and only that pair, is the price you are about to deal with.