What is the effect of a cancelled stock order on a stock and the market?
"That article, like almost any article written by a non-expert and quoting only ""research"" from lobbying groups, hugely misses the point. The vast majority of orders that end up being cancelled are cancelled as a standard part of exchanges' official market-maker programs. Each exchange wants you and me to know that it has liquidity -- that when we go to buy or sell some stock, there will be someone waiting on the other side of the trade.  So the exchange pays (via lowered fees or even rebates) hundreds of registered market makers to constantly have orders resting in each product's order book within a few ticks of the current NBBO or the last trade price.  That way, if everyone else should suddenly disappear from the market, you and I will still be able to trade our shares for a price somewhat close to the last trade price. But market makers who are simply acting in this ""backstop"" role don't actually want to have their orders filled, because those orders will almost always lose them money. So as prices rise and fall (as much as tens of times per second), the market makers need to cancel their resting orders (so they don't get filled) and add new ones at new prices (so they meet their obligations to the exchange).  And because the number of orders resting in any given product's order book is vastly larger than the number of actual trades that take place in any given time period, naturally the number of cancellations is also going to hugely outweigh the number of actual trades.  As much as 97% to 3% (or even more). But that's completely fine! You and I don't have to care about any of that.  We almost never need the market makers to be there to trade with us.  They're only there as a backstop.  There's almost always plenty of organic liquidity for us to trade against.  Only in the rare case where liquidity completely dries up do we really care that the registered market makers are there.  And in those cases (ideally) the market makers can't cancel their orders (depending on how well the exchange has set up its market maker program). So, to answer your question, the effect of standard order cancellation on a stock is essentially none.  If you were to visualize the resting orders in a product's book as prices moved up and down, you would essentially see a Gaussian distribution with mean at the last trade price, and it would move up and down with the price.  That ""movement"" is accomplished by cancellations followed by new orders. P.S. As always, keep in mind that your and my orders almost never actually make it to a real stock exchange anymore.  Nowadays they are almost always sent to brokers' and big banks' internal dark pools.  And in there you and I have no idea what shenanigans are going on.  As just one example, dark pools allow their operators and (for a fee) other institutional participants access to a feature called last look that allows them to cancel their resting order as late as after your order has been matched against it! :( Regarding the question in your comment ... If Alice is sending only bona fide orders (that is, only placing an order at time T if, given all the information she has at time T, she truly wants and intends for it to be filled) then her cancellation at a later time actually adds to the effectiveness of and public perception of the market as a tool for price discovery (which is its ultimate purpose). [In the following example imagine that there are no such things as trading fees or commissions or taxes.] Let's say Alice offers to buy AAPL at $99.99 when the rest of the market is trading it for $100.00.  By doing so she is casting her vote that the ""fair value"" of a share of AAPL is between $99.99 and $100.00. After all, if she thought the fair value of a share of AAPL was higher --  say, between $100.00 and $100.01 -- then she should be willing to pay $100.00 (because that's below fair value) and she should expect that other people in the market will not soon decide to sell to her at $99.99. If some time later Alice does decide that the fair value of AAPL is between $100.00 and $100.01 then she should definitely cancel her order at $99.99, for exactly the reason discussed above.  She probably won't get filled at $99.99, and by sitting there stubbornly she's missing out (potentially forever) on the possibility to make a profit. Through the simple act of cancelling her $99.99 order, Alice is once again casting a vote that she no longer thinks that's AAPL's fair value.  She is (very slightly) altering the collective opinion of the entire market as to what a share of AAPL is worth.  And if her cancellation then frees her up to place another order closer to her perceived fair value (say, at $100.00), then that's another vote for her honest optinion about AAPL's price. Since the whole goal of the market is to get a bunch of particpants to figure out the fair value of some financial instrument (or commodity, or smart phone, or advertising time, etc.), cancellations of honest votes from the past in order to replace them with new, better-informed honest votes in the present can only be a good thing for the market's effectiveness and perceived effectiveness. It's only when participants start sending non-honest votes (non bona fide orders) that things start to go off the rails.  That's what @DumbCoder was referring to in his comment on your original question."
Context is key here. Futures don't really have to do with a time in the future in this context.  Futures are a capital market (futures market), just like Stocks are a market (stock market). Both capital markets have the ability to affect each other. Up until 30 years ago there was a separate use for the futures market, but in the days since they are MOSTLY used for stock derivatives (financial futures are the most widely traded contracts since 1980, hugely eclipsing the commodity futures that the market was designed for.)  So there is overlap and one affect the other, I'm not going to go into too much detail here but basically the futures market trades 24 hours a day, 6.5 days of the week and the  stock market trades 8-12 hours a day, 5 days a week.  So when the stock market closes, the futures market is still running will react and effect the broad stock market.  Hope that gets you started in your research "EDIT: It was System Disruption or Malfunctions August 24, 2015 2:12 PM EDT   Pursuant to Rule 11890(b) NASDAQ, on its own motion, in conjunction   with BATS, and FINRA has determined to cancel all trades in security   Blackrock Capital Investment. (Nasdaq: BKCC) at or below $5.86 that   were executed in NASDAQ between 09:38:00 and 09:46:00 ET. This   decision cannot be appealed. NASDAQ will be canceling trades on the   participants behalf. A person on Reddit claimed that he was the buyer. He used Robinhood, a $0 commission broker and start-up.  The canceled trades are reflected on CTA/UTP and the current charts will differ from the one posted below.  It is an undesired effect of the 5-minute Trading Halt.  It is not ""within 1 hour of opening, BKCC traded between $0.97 and $9.5"".  Those trades only occurred for a few seconds on two occasions.  One possible reason is that when the trading halt ended, there was a lot of Market Order to sell accumulated.  Refer to the following chart, where each candle represents a 10 second period. As you can see, the low prices did not ""sustain"" for hours.   And the published halts." Your three options are: Options 2 and 3 are obviously identical (other than transaction costs), so if you want to keep the stock, go for option 1, otherwise, go for option 3 since you have the same effect as option 2 with no transaction costs.  The loss will likely also offset some of the other short term gains you mentioned. "I'm adding to @Dilip's basic answer, to cover the additional points in your question.  I'll assume you are referring to publicly traded stock options, such as those found on the CBOE, and not an option contract entered into privately between two specific counterparties (e.g. as in an employer stock option plan). Since you are not obligated to exercise a call option you purchased on the market, you don't need to maintain funds on account for possible exercising.  You could instead let the option expire, or resell the option, neither of which requires funds available for purchase of the underlying shares. However, should you actually choose to exercise the call option (and usually this is done close to expiration, if at all), you will be required to fund your account much like if you bought the underlying shares in the first place.  Call your broker to determine the exact rules and timing for when they need the money for a call-option exercise. And to expand on the idea of ""cancelling"" an option you purchased: No, you cannot ""cancel"" an option contract, per se.  But, you are permitted to sell the call option to somebody else willing to buy, via the market.  When you sell your call option, you'll either make or lose money on the sale – depending on the price of the underlying shares at the time (are they in- or out- of the money?), volatility in the market, and remaining time value.  Once you sell, you're back to ""no position"".  That's not the same as ""cancelled"", but you are out of the trade, whether at profit or loss. Furthermore, the option writer (i.e. the seller who ""sold to open"" a position, in writing the call in the first place) is also not permitted to cancel the option he wrote.  However, the option writer is permitted to close out the original short position by simply buying back a matching call option on the market.  Again, this would occur at either profit or loss based on market prices at the time.  This second kind of buy order – i.e. made by someone who initially wrote a call option – is called a ""buy to close"", meaning the purchase of an offsetting position.  (The other kind of buy is the ""buy to open"".) Then, consider: Since an option buyer is free to re-sell the option purchased, and since an option writer (who ""sold to open"" the new contract) is also free to buy back an offsetting option, a process known as clearing is required to match remaining buyers exercising the call options held with the remaining option writers having open short positions for the contract.  For CBOE options, this clearing is performed by the Options Clearing Corporation.  Here's how it works (see here): What is the OCC? The Options Clearing Corporation is the sole issuer of all securities   options listed at the CBOE, four other U.S. stock exchanges and the   National Association of Securities Dealers, Inc. (NASD), and is the   entity through which all CBOE option transactions are ultimately   cleared. As the issuer of all options, OCC essentially takes the   opposite side of every option traded. Because OCC basically becomes   the buyer for every seller and the seller for every buyer, it allows   options traders to buy and sell in a secondary market without having   to find the original opposite party.   [...]   [emphasis above is mine] When a call option writer must deliver shares to a call option buyer exercising a call, it's called assignment.  (I have been assigned before, and it isn't pleasant to see a position called away that otherwise would have been very profitable if the call weren't written in the first place!) Also, re: ""I know my counter party cannot sell his shares"" ... that's not strictly true.  You are thinking of a covered call.  But, an option writer doesn't necessarily need to own the underlying shares.  Look up Naked call (Wikipedia).  Naked calls aren't frequently undertaken because a naked call ""is one of the riskiest options strategies because it carries unlimited risk"".  The average individual trader isn't usually permitted by their broker to enter such an order, but there are market participants who can do such a trade. Finally, you can learn more about options at The Options Industry Council (OIC)." They put their stock on the market that people then purchased, if they don't put that stock out there then I suspect those people will just buy the stock from somewhere, so really no harm was caused to any individual that would have been prevented otherwise.   It's not great, and shouldn't be done as market asssumtry isn't good. I think the punishments for if aren't to right any sort of wrongdoing, it's to act as a deterrent. The short answer to your question is yes.  Company performance affects stock price only through investors' views. But note that selling for higher and lower prices when the company is doing well or poorly is not an arbitrary choice.  A stock is a claim on the future cash flows of the firm, which ultimately come from its future profits.  If the company is doing well, investors will likely expect that there will large cash flows (dividends) in the future and be willing to pay more to hold it (or require more to sell it).   The price of a stock is equal what people think the future dividends are worth.  If market participants started behaving irrationally, like not reacting to changes in the expected future cash flows, then arbitrageurs would make a ton of money trading against them until the situation was rectified. There are a few scenarios I see possible:  1. Risk parameters in the algo were set very conservatively. Putting quotes out and canceling them is very common.   2. It was looking to exploit situations where someone rips through the book with a market order.  3. It was reacting too slowly to signals, and chasing opportunities that had already passed.   Other comments: What do you believe front running is? Your version differs from the textbook definition.   Quote taxes are more effective than minimum order durations. I wrote about how that works in a previous post in this thread. As stock prices have declined, the net worth of people has come down. Imagine owning a million shares of a stock worth $100/share. This is worth $100,000,000. Now, if the stock is suddenly trading at $50/share then some would say you have lost $50,000,000. The value of the stock is less. The uncertainty is always there as there are differences between one day's close and another day's open possibly. The sale price is likely to be near the last trade is what is being used here. If you place a market order to sell your stock, the price may move between the time the order is placed and when it is filled. There are limit orders that could be used if you want to control the minimum price you get though you give up that the order has to be filled as otherwise people could try to sell shares for millions of dollars that wouldn't work out well. The opening price is derived from new information received. It reflects the current state of the market. Opening Price Deviation (from Investopedia): Investor expectation can be changed by corporate announcements or   other events that make the news. Corporations typically make   news-worthy announcements that may have an effect on the stock price   after the market closes. Large-scale natural disasters or man-made   disasters such as wars or terrorist attacks that take place in the   afterhours may have similar effects on stock prices. When this   happens, some investors may attempt to either buy or sell securities   during the afterhours. Not all orders are executed during after-hours trading. The lack of   liquidity and the resulting wide spreads make market orders   unattractive to traders in after-hours trading. This results in a   large amount of limit or stop orders being placed at a price that is   different from the prior day’s closing price. Consequently, when the   market opens the next day, a substantial disparity in supply and   demand causes the open to veer away from the prior day’s close in the   direction that corresponds to the effect of the announcement, news or   event. Does the market automatically assume a rescheduled call means something major, like the auditors aren't signing the financials, is going on? Yes. (If so, why?) People - including investors - are emotional. And suspicious. And paranoid. Financial discussions tend to make everything sound like a cold, clinical science, and to some degree that is true. But you should never look past something much more simple - people are people. And of course, once all is said and done, acts like a reschedule often do mean something is up. So you've now got a nice mix of fact and emotion.   Does it mean that 95% of the shares' holders are insiders who all decided to sell when they learned about whatever is causing the delay in the con call? No. See Littleadv's answer. Volatility typically decreases when stocks rise except pending news events or fast markets.  It has a great impact of the premium of the option. I hate attributing an event like this to a single cause.  That implies that the market is an orderly system where everything operates smoothly.  I prefer to see it as much chaotic. When I see a drop like that happen, I'd say that there were a lot of sellers of stocks and all the buyers were bidding less and less for those few minutes.  Perhaps the catalyst for that was a typo or a strange order.  But in the end all the participants in the market responded by bidding down stocks, not just one person.  It takes sides to complete a trade. I know my model is a bit simplistic...  I'd be happy if someone corrected me :-) Ideally, stock price reflects the value of the company, the dividends it is expected to pay, and what people expect the future value of the company to be. Only one of those (maybe one and a half) is related to current  sales, and not always directly. Short-term motion of a stock is even less directly linked, since it also reflects previous expectations. A company can announce disappointing sales and see its stock go up, if the previous price was based on expecting  worse news. If you are in a position to have information that will impact the shares of a stock or index fund and you use that information for either personal gain or to mitigate the losses that you would have felt then it is insider trading.  Even if in the end your quiet period passes with little or no movement of the stocks in question.  It is the attempt to benefit from or the appearance of the attempt to benefit from inside information that creates the crime.  This is the reason for the quiet periods to attempt to shield the majority of the companies employees from the appearance of impropriety, as well as any actual improprieties. With an index you are running a double edged sword because anything that is likely to cause APPLE to drop 10% is likely to give a bump to Motorola, Google, and its competitors.  So you could end up in jail for Insider trading and lose your shirt on a poor decision to short a Tech  ETF on knowledge that will cause Apple to take a hit.  It is certainly going to be harder to find the trade but the SEC is good at looking around for activity that is inconsistent with normal trading patterns of individuals in a position to have knowledge with the type of market impact you are talking about. Insiders (those who are aware of non-public material information, not necessarily employees) are the ones who actually cannot sell once they learned about whatever, by law. Martha Stewart went to jail for that. Any such deviation from the norm triggers abnormal response and avalanche of rumors, so by default investors assume something bad and try to minimize the loss. When dealing with a tiny company (market cap of less than 15M) with a tiny market volume (6.2M), the swings can be very significant. For such a small company, it is safe to assume that something happened that lead them to delay the conference call, and since they didn't tell what happen, investors assume the worst. It might end up as the CEO and CFO having bad stomach after celebrating 100% growth in revenue they were going to announce, but you'll have to wait and see....