Trading glossaryReviewed 16 July 2026
Definition
A fill is the executed portion of an order, identified by quantity, price, time, and other transaction details reported by the executing venue.
In market context
An order can fill completely in one transaction or receive several partial fills at different prices. The average execution price combines those fills, while unfilled quantity may remain pending, expire, or be cancelled according to the instruction. Reviewing fills matters because the final position, fees, and P&L are based on executed quantities rather than the amount originally requested by the account.
Source
Use the primary source for fuller regulatory or market context.