What it means
Ordinary limit orders can sit on an exchange for hours and fill in pieces as buyers and sellers appear. A fill or kill order removes both of those features, demanding the full quantity in a single moment and cancelling itself if the market cannot supply it.
The whole decision happens in the instant the order reaches the exchange. Traders reach for it when partial execution creates a real problem rather than a minor inconvenience.
If you need 20,000 shares to complete a hedge and only 8,000 arrive, you are left holding an unbalanced position and still have to buy the rest, probably at a worse price. Cancelling cleanly and trying again is often the better outcome.
It also serves as a discreet way of testing available liquidity without leaving a footprint. An order that appears and vanishes within a second reveals far less about a large buyer's intentions than one that rests visibly on the order book for twenty minutes.
Institutional desks use this deliberately when building or unwinding sizeable positions. Fill or kill sits alongside two similar instructions that are easy to confuse.
Immediate or cancel accepts a partial fill and cancels the remainder, while all or none demands the full quantity but is willing to wait rather than cancel. Fill or kill is simply the combination of both conditions, all of it and right now.
The obvious cost is a lower chance of trading at all, and in a thin market a fill or kill order may be cancelled repeatedly without ever executing. That is the intended trade-off: the instruction buys certainty about the shape of the trade at the price of certainty about whether it happens.
In highly liquid large-cap shares the difference is negligible, while in small caps and less-traded bonds it can be the difference between trading and not.
In practice
Real-world examples.
Example
A hedge fund needs to short 50,000 shares of a mid-cap company as the second leg of a pairs trade it has just entered. It uses fill or kill so that a partial fill cannot leave the strategy half built and directionally exposed.
Example
A corporate treasurer buying back company shares under a defined mandate wants a single clean block rather than a trail of small executions that would complicate the disclosure. She instructs the broker to work a fill or kill order at a specified limit.
Example
A trader in a thinly traded bond issues three fill or kill orders across a morning, all of which are cancelled for lack of size. The repeated cancellations tell him the market is far thinner than the screen prices suggested, and he revises his exit plan accordingly.
Think of it
“Fill or kill means all or nothing, right now-complete fill or automatic cancel.
Formula
Calculation
Order value if executed = quantity x limit price
A fund manager places a fill or kill order to buy 20,000 shares at a limit price of $18.50. If the order executes in full, the cost is 20,000 x $18.50 = $370,000 before commission.
When the order reaches the exchange, only 12,000 shares are available at $18.50 or better. Under a normal limit order the trader would take those 12,000 shares for 12,000 x $18.50 = $222,000 and wait for the rest. Under a fill or kill instruction the entire order is cancelled instead, the manager buys nothing, and no commission is paid.
The manager retries an hour later when 24,000 shares are showing at $18.50. This time the full 20,000 executes and the cost is exactly $370,000, with the remaining 4,000 shares of supply left untouched on the book.Case study
Seen in the real world.
The following scenario is fictional and offered only as an illustration. Redhill Convertible Fund, an invented boutique fund, ran a strategy that required buying a convertible bond and simultaneously shorting the underlying equity in a fixed ratio. Its dealing desk had habitually used ordinary limit orders on the equity leg.
Over one volatile quarter the fictional desk was left with partial equity hedges on eleven separate occasions, and the unhedged exposure that resulted cost the fund an estimated $310,000 as prices moved before the balance could be filled. A review concluded that the losses came not from bad price selection but from accepting incomplete executions.
Redhill's illustrative response was to make fill or kill the default on every hedging leg above 10,000 shares. The desk's execution rate fell noticeably and traders complained about missed opportunities, but the tracking error between the two legs of the strategy narrowed sharply over the following two quarters.
Watch out
Common mistakes.
- Using fill or kill for routine orders in liquid shares, where it adds no benefit and occasionally cancels a perfectly good trade for no reason.
- Confusing fill or kill with immediate or cancel, when the latter is happy to take a partial fill and only the former insists on everything.
- Interpreting a cancelled fill or kill order as evidence the price was wrong, when it usually only means the size was not there at that instant.
Questions
People also ask.
Does a cancelled fill or kill order cost anything?
Usually nothing beyond the time spent, since brokers generally charge commission only on executed trades, though platform terms vary.
Can retail investors use fill or kill?
Most mainstream brokers offer it, but it is rarely useful for small orders in liquid shares because the full quantity is almost always available anyway.
What is the difference between fill or kill and all or none?
All or none insists on the full quantity but will wait on the order book for it, while fill or kill insists on the full quantity immediately and cancels if it cannot get it.
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