A partial fill happens when only part of your order executes. The remaining quantity stays open (pending) or is cancelled, depending on your order settings and the market’s available liquidity.
In plain English: “I asked for 10 units, but only 6 were available right now.”
Partial fills are normal in real markets. The key is understanding when they matter and how to manage them.
Markets are built on available liquidity at each price level. If your order size is bigger than what’s available at your price, it may fill in pieces.
On exchange-traded markets, partial fills are visible because the order book is real. In OTC products (like many CFDs), the broker may internalise or source liquidity from providers — which can change how partial fills appear.
Partial fills can change execution quality and trade management:
For small retail sizes on liquid instruments, partial fills are often rare. They become more common in thin markets, large size, or high volatility.
When an order fills in parts at different prices, your platform typically shows a single average entry/exit price. This is usually a volume-weighted average price (VWAP).
Average Price = (Fill1Price × Fill1Size + Fill2Price × Fill2Size + …) ÷ (Total Size)
This ensures bigger fills influence the average more than smaller fills.
Your stop-loss distance, risk per trade, and performance metrics are based on the average price. If you ignore this, your risk calculations can be wrong.
You place a buy limit for 1,000 shares at £10.00. At £10.00, only 400 shares are available immediately.
Result: you have a smaller position than planned, which changes your risk and target calculations.
Partial fills are not always “bad”, but if you want fewer of them:
If your strategy depends on exact size and price, avoid trading during high volatility and keep sizes modest until you understand your platform’s execution behaviour.
Try answering before expanding the model answers.
Not enough liquidity available for your full size at your price (or during your execution window).
As one position with an average (volume-weighted) entry/exit price.
Trade more liquid instruments, reduce order size, avoid volatile periods, or use IOC/FOK where available.
If you can explain these points, you understand why partial fills occur and how to manage them sensibly.
They can happen with both. Limit orders may partially fill at the limit price if limited size is available there. Market orders can fill across multiple price levels, which can also appear as multiple fills.
Sometimes. On some venues/brokers, multiple fills can mean multiple commission charges or slightly different fees. On others, costs are aggregated. Check your broker’s fee model.
First, confirm your actual position size and average price. Then check your stop-loss and take-profit sizes. Finally, decide whether to leave the remainder working, amend it, or cancel it.
Not always. You can reduce the likelihood by trading liquid markets and sizing appropriately. On some venues you can use FOK to prevent partial fills, but that increases no-fill risk.
Partial fills happen when the market cannot execute your full order size at your price (or during your execution window). They are a normal liquidity effect and become more common with larger sizes, thin markets, and volatility.
The key is to manage the consequences: confirm your filled size, check your average price, and ensure your risk controls match the actual position.
Remaining lessons in this set: Good Till Cancelled (GTC) (done), Fill or Kill (done), and any platform-specific variations you want to add next.