What it means
A partial fill occurs when the available counterparty volume at your requested price is less than your order size. Your order fills for whatever volume is available; the remainder either rests in the book (limit orders) or cancels (IOC orders), depending on time-in-force. Common on large orders in less-liquid pairs or during off-hours.
Why it matters
Partial fills break any strategy that assumes 'fill or no fill' binary execution. For position sizing, partial fills mean the actual realized exposure is smaller than planned — and any stop/take-profit sized to the full position is now mis-scaled. For algorithmic strategies, partial-fill logic is a required feature, not an edge case.
How to use it
For each order, decide upfront whether partial fills are acceptable (limit-based scaling in/out: yes) or unacceptable (fixed-size entries: no, use IOC). Adjust bracket orders to match the actual filled size after partials. For large orders, prefer scaling in via multiple smaller limits over single block orders.
Want a worked example or a deeper dive? Ask Rocky how this concept applies to your specific watchlist or trade idea.
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