Partial Fill
The execution of only part of an order's quantity, with the remainder either resting in the book or cancelled.
Formula
Filled Quantity < Order Quantity, with the unfilled balance either resting or cancelled per the order's validity
Unit
shares
In depth
Partial fills are the normal state of affairs for any order larger than the depth at its price, and each fill can occur at a different price, producing a blended average. This matters for cost accounting, since brokers charging per execution multiply the fee, and for tax, since each lot carries its own acquisition date under first-in-first-out. Traders who mentally treat a position as complete before checking the fill quantity end up with unhedged or undersized exposure. All-or-none and immediate-or-cancel instructions exist precisely to control what happens to the unfilled balance.
Worked example
An order for 2,000 shares fills 800 at ₹250.10 and 500 at ₹250.30, leaving 700 open. The position is 1,300 shares at an average of (800 x 250.10 + 500 x 250.30) / 1,300 = ₹250.18, not the 2,000 shares intended.
Illustrative figures, chosen so the arithmetic is easy to follow. Not a live price and not a valuation of any company.
Educational reference only
This entry explains what “Partial Fill” means. It is not investment advice and not a recommendation to buy or sell any security. Any numbers above are illustrative, not live prices, and nothing here predicts price direction or rates a stock. Consider your own circumstances and consult a SEBI-registered investment adviser before acting.