Partial Fill

A partial fill occurs when the market can only supply some of your order's size at your price; you receive the shares that were available, and the remainder either keeps working or cancels, depending on the order's time-in-force and instructions. It is the routine outcome of placing size in a thin book.

Partials create a decision, not just an execution. Holding a fraction of your intended position changes the risk math: your planned stop now protects a smaller position, and completing the position later usually means paying up. An immediate-or-cancel (IOC) instruction fills what it can instantly and kills the rest, which at least makes the leftover explicit.