Definition
A fill occurs when an order actually trades, rather than merely being accepted or triggered. An order can have one fill or several. Execution records commonly state the quantity, price, time, and fee associated with each fill.
How It Works
If a hypothetical order buys 1 unit at 100 USDT and another at 102, it has two fills and a quantity-weighted average price of 101 USDT before fees. The order is fully filled only when its entire requested quantity has executed. A trigger notification alone does not prove that this happened.
Key Considerations
Check fills rather than the original order price when calculating cost and exposure. Cancellation affects only an eligible unfilled remainder. Execution on a custodial exchange updates account balances; it does not necessarily mean an external blockchain withdrawal or final bank transfer has taken place.