Usage of a sell stop order
It depends to some extent on how you interpret the situation, so I think this is the general idea. Say you purchase one share at $50, and soon after, the price moves up, say, to $55. You now have an unrealized profit of $5. Now, you can either sell and realize that profit, or hold on to the position, expecting a further price appreciation. In either case, you will consider the price change from this traded price, which is $55, and not the price you actually bought at. Hence, if the price fell to $52 in the next trade, you have a loss of $3 on your previous profit of $5. This (even though your net P&L is calculated from the initial purchase price of $50), allows you to think in terms of your positions at the latest known prices. This is similar to a Markov process, in the sense that it doesn't matter which route the stock price (and your position's P&L) took to get to the current point; your decision should be based on the current/latest price level.
"Well, they don't have to enter a market order. I was just saying that for your benefit.   In practice what will really happen is they'll say to themselves   ""I want ABC for no more than 70.00""  The current bid is at 69.60 They'll use a limit order on 10,000 shares. If anyone offers them more than 70.00 the computer program they're using will not accept.  However, the shares won't be bought all at once. A limit order for 10,000 shares will be spit into 1,000 shares at 69.70 and 10,000 for 69.65  The HFT can then make a reasonable guess someone is buying in bulk. So then the HFT sends out a sell order saying ""10 shares at 70.10"". The guy doesn't want that so they do it over again at 70.09  Eventually they notice when the guy accepts at 70.00  So now they knew this guy is willing to pay that. Then HFT buys all the shares they can. ALL SHARES, not just the amount the guy wants. They buy it all at 69.95, which is higher than the 69.70 the guy just paid or whatever.  They then sell it all back to the guy at 70.00  The guy has no choice because all the shares are now gone. He has to pay his highest price.   Once the guy gets his order the HFT just dumps the rest of the shares back at the price they bought them at.  edit: Another way to pull this off is to just literally build your own exchange. Then you can do all of this without any clever tricks. You can just outright give yourself preference over everyone else because you can truly decide what order the trades are being executed." Stop order is shorter term for stop-loss order.  The point being that is intended as a protective measure.  A buy stop order would be used to limit losses when an investor has sold a stock short.  (Meaning that they have borrowed stock and sold it, in hopes that they can take advantage of a decline in the stock's price by replacing the borrowed stock later at a cheaper price.  The idea is to limit losses due to a rising stock price.)  Meanwhile, a sell stop order would be used to limit losses on a stock that an investor actually owns, by selling it before the price declines further. The important thing to keep in mind about stop orders is that they turn into market orders when the stop price is reached.  This means that they will be filled at the best available price when the order is actually executed.  In fast moving markets, this can be a price that is quite different from the stop price. A limit order allows an investor to ensure that they do not buy/sell a stock at more/less than the specified amount. The thing to keep in mind is that a limit order is not guaranteed to execute. A stop-limit order is a combination of a stop-loss order and limit order, in that it becomes a limit order (instead of a market order) when the stop price is reached. Links to definitions: Stop order Stop-limit order Limit order Market order Do not use a stop loss order as a long-term investor.  The arguments in favor of stop losses being presented by a few users here rely on a faulty premise, namely, that there is some kind of formula that will let you set your stop such that it won't trigger on day-to-day fluctuations but will trigger in time to protect you from a significant loss in a serious market downturn.  No such formula exists.  No matter where you set your stop, it is as likely to dump you from your investment just before it begins climbing again as it is to shield you from continued losses.  Each time that happens, you will have sold low and bought high, incurring trading fees into the bargain.  It is very unlikely that the losses you avoid in a bear market (remember, you still incur the loss up until your stop is hit; it's only the losses after that that you avoid) will make up the costs of false alarms. On top of that, once you have stopped out of your first investment choice, then what?  Will you reinvest in some other stock or fund?  If those investments didn't look good to you when you first set up your asset allocation, then why should they look any better now, just because your primary investment has dropped by some arbitrary[*] amount?  Will you park the money in cash while you wait for prices to bottom out?  The market bottom is only apparent in retrospect.  There is no formula for calling it in real time. Perhaps stop loss orders have their uses in active trading strategies, or maybe they're just chrome that trading platforms use to attract customers.  Either way, using them on long-term investments will just cost you money in the long run.  Forget the fancy order types, and manage your risk through your asset allocation.  The overwhelming likelihood is that you will get better performance, and you will spend less time worrying about your investments to boot. [*] Why are the stop levels recommended by the formulae invariably multiples of 5%?  Do the market gods have a thing for round numbers? Brokerage firms must settle funds promptly, but there's no explicit definition for this in U.S. federal law. See for example, this article on settling trades in three days. Wikipedia also has a good write-up on T+3. It is common practice, however. It takes approximately three days for the funds to be available to me, in my Canadian brokerage account. That said, the software itself prevents me from using funds which are not available, and I'm rather surprised yours does not. You want to be careful not to be labelled a pattern day trader, if that is not your intention. Others can better fill you in on the consequences of this. I believe it will not apply to you unless you are using a margin account. All but certainly, the terms of service that you agreed to with this brokerage will specify the conditions under which they can lock you out of your account, and when they can charge interest. If they are selling your stock at times you have not authorised (via explicit instruction or via a stop-loss order), you should file a complaint with the S.E.C. and with sufficient documentation. You will need to ensure your cancel-stop-loss order actually went through, though, and the stock was sold anyway. It could simply be that it takes a full business day to cancel such an order. "The question mentions a trailing stop. A trailing stop is a type of stop loss order. It allows you to protect your profit on the stock, while ""keeping you in the stock"". A trailing stop is specified as a percentage of market price e.g. you might want to set a trailing stop at 5%, or 10% below the market price. A trailing stop goes up along with the market price, but if the market price drops it doesn't move down too. The idea is that it is there to ""catch"" your profit, if the market suddenly moves quickly against you. There is a nice explanation of how that works in the section titled Trailing Stops here. (The URL for the page, ""Tailing Stops"" is misleading, and a typo, I suspect.)" You will lose out on your spread, you always pay a spread. Also, if you are looking at a strategy for using stop losses, try taking into account the support lines if you are going long. So, if the stock is on an upward trend but is dropping back from profit taking, your best best is to take a position closest to the next support line. You place your stop just below the support. this will give you the best chance of a winning position as most technical analysts will have looking towards the support as a buy back area. Obviously, in a bear market the opposite is true.  If you have taken your position and the market move past the first resistance line, then bring your stop to just below that line as once resistance is broken, it then becomes support. You then have a profitable position with profit locked in. Leave the position to break the next resistance and repeat. "[This is the simple solution.](http://market-ticker.org/akcs-www?singlepost=3041628)  ""Since the Securities and Exchange Act requires that all orders must be intended to execute there's a simple way to prevent this sort of nanosecond game, where any part of the strategy involves ""flashing"" an order that isn't really intended to execute and thus clear through the exchange: Force all orders to be valid for two full seconds or until executed.""" The price doesn't have to drop 5% in one go to activate your order. The trailing aspect simply means your sell trigger price will increase if the current value increases (it will never decrease). You have no guarantees. The stock may last have traded at $100 (so, the market price is $100), but is currently in free-fall and nobody else will be willing to buy it for any more than $80. Or heck, maybe nobody will be willing to buy it at all, at any price. Or maybe trading on this stock will be halted. Remember, the market price is just what the stock last traded at. If you put in a 'market order', you are ordering your broker to sell at the best available current price. Assuming someone's willing to buy your stock, that means you'll sell it. But if it last traded at $100, this doesn't guarantee you'll sell at anything close to that. From the non-authoritative Investopedia page: A stop-limit order will be executed at a specified price, or better, after a given stop price has been reached. Once the stop price is reached, the stop-limit order becomes a limit order to buy or sell at the limit price or better. So once the stop price has been breached, your limit order is placed and will be on the order books as a $9 ask. For a vanilla stop order, a market order will be placed and will be filled using the highest active bid(s). The order book looks fine, if it were a liquid market. However, a bid that matches with an ask will always be met on a first come first serve basis. There's no other way to do it.   Most traders don't like doing that because they want to try to get a lower price. HFT don't have to worry about meeting the ask because they're just going to pass that cost on to the guy on the hook.   By the time the HFT makes the buy they already know the guy wants to buy at 70.00  They did not know that at the time they placed the buy order. If the buy order from the HFT hasn't been cancelled it means they already found someone.  How? By testing the market with sell orders at the same time they were sending buy orders.  They keep a little bit of stock in reserve to perform these tests. "Yes it is possible, as long as the broker you use allows conditional orders. I use CMC Markets in Australia, and they allow free conditional orders either when initially placing a buy order or after already buying a stock. See the Place New Order box below:  Once you have selected a stock to buy, the number of shares you want to buy and at what price you can place up to 3 conditional orders. The first condition is a ""Place order if..."" conditional order. Here you can place a condition that your buy order will only be placed onto the market if that condition is met first.  Say the stock last traded at $9.80 and you only want to place your order the next day if the stock price moves above the current resistance at $10.00. So you would Place order if Price is at or above $10.00. So if the next day the price moves up to $10 or above your order will be placed onto the market. The second condition is a ""Stop loss"" conditional order. Here you place the price you want to sell at if the price drops to or past your stop loss price. It will only be placed on to the market if your buy order gets traded. So if you wanted to place your stop loss at $9.00, you would type in 9.00 in the box after ""If at or below ?"" and select if you want a limit or market order. The third condition is a ""Take profit"" conditional order. This allows you to take profits if the stock reaches a certain price. Say you wanted to take profits at 50%, that is if the price reached $15.00. So you would type in 15.00 in the box after ""If at or above ?"" and again select if you want a limit or market order. These conditional orders can all be placed at the time you enter your buy order and can be edited or deleted at any time. The broker you use may have a different process for entering conditional orders, and some brokers may have many more conditional orders than these three, so investigate what is out there and if you are confused in how to use the orders with your broker, simply ask them for a demonstration in how to use them." On most exchanges, if you place a limit order to sell at 94.64, you will be executed before the market can trade at a higher price. However most stocks in the US trade across several exchanges and your broker won't place your limit order on all exchanges (otherwise you could be executed several times). The likeliest reason for wht happened to you is that your order was not on the market where those transactions were executed. Reviewing the ticks, there were only 8 transactions above your limit, all at 1:28:24, for a total 1,864 shares and all on the NYSE ARCA exchange. If your order was on a different exchange (NYSE for example) you would not have been executed. If your broker uses a smart routing system they would not have had time to route your order to ARCA in time for execution because the market traded lower straight after. Volume at each price on that day: "There are two distinct questions that may be of interest to you. Both questions are relevant for funds that need to buy or sell large orders that you are talking about. The answer depends on your order type and the current market state such as the level 2 order book. Suppose there are no iceberg or hidden orders and the order book (image courtesy of this question) currently is:  An unlimited (""at market"") buy order for 12,000 shares gets filled immediately: it gets 1,100 shares at 180.03 (1,100@180.03), 9,700 at 180.04 and 1,200 at 180.05. After this order, the lowest ask price becomes 180.05 and the highest bid is obviously still 180.02 (because the previous order was a 'market order'). A limited buy order for 12,000 shares with a price limit of 180.04 gets the first two fills just like the market order: 1,100 shares at 180.03 and 9,700 at 180.04. However, the remainder of the order will establish a new bid price level for 1,200 shares at 180.04. It is possible to enter an unlimited buy order that exhausts the book. However, such a trade would often be considered a mis-trade and either (i) be cancelled by the broker, (ii) be cancelled or undone by the exchange, or (iii) hit the maximum price move a stock is allowed per day (""limit up""). Funds and banks often have to buy or sell large quantities, just like you have described. However they usually do not punch through order book levels as I described before. Instead they would spread out the order over time and buy a smaller quantity several times throughout the day. Simple algorithms attempt to get a price close to the time-weighted average price (TWAP) or volume-weighted average price (VWAP) and would buy a smaller amount every N minutes. Despite splitting the order into smaller pieces the price usually moves against the trader for many reasons. There are many models to estimate the market impact of an order before executing it and many brokers have their own model, for example Deutsche Bank. There is considerable research on ""market impact"" if you are interested. I understand the general principal that when significant buy orders   comes in relative to the sell orders price goes up and when a   significant sell order comes in relative to buy orders it goes down. I consider this statement wrong or at least misleading. First, stocks can jump in price without or with very little volume. Consider a company that releases a negative earnings surprise over night. On the next day the stock may open 20% lower without any orders having matched for any price in between. The price moved because the perception of the stocks value changed, not because of buy or sell pressure. Second, buy and sell pressure have an effect on the price because of the underlying reason, and not necessarily/only because of the mechanics of the market. Assume you were prepared to sell HyperNanoTech stock, but suddenly there's a lot of buzz and your colleagues are talking about buying it. Would you still sell it for the same price? I wouldn't. I would try to find out how much they are prepared to buy it for. In other words, buy pressure can be the consequence of successful marketing of the stock and the marketing buzz is what changes the price." Yes, you can do this buy placing a conditional order to buy at market if the price moves to 106 or above. Once the price hits 106 your market order will hit the market and you will purchase the stock at 106 or above. You can also place a tack profit order at 107 linked to your initial conditional buy order, so that once you buy order is executed and you buy at 106, a take profit order will be executed only if the price reaches 107 or above.  If the price never reaches 106, neither your market buy order or take profit order will hit the market and you won't buy or sell anything.