How will a limit order be executed when the stock market opens if there is a large change from the price of the day before?
The next day the market opens trading at 10.50, You haven't specified whether you limit order for $10.10 is to buy or sell. When the trading opens next day, it follows the same process of matching the orders. So if you have put a limit order to buy at $10.10 and there is no sell order at that price, your trade will not go through. If you have placed a limit sell order at $10.10 and there is a buyer at or higher price, it would go through. The Open price is the price of the first trade of the day.
Should do it through a limit auction book.   Management and shareholders pre ipo submit sealed limit sell orders. Buyers submit sealed limit buy orders, nobody can see where the price is going.  At 9AM, the price is calculated and whomever fills get filled and ta da everyone is trading at 9:30 when the market is open. I'd add, this is actually the way any stock opens every day, i.e. the closing price of the prior day is what it is, but the opening price will reflect whatever news there was prior to the day's open. If you watch the business news, you'll often see that some stock has an order imbalance and has not opened yet, at the normal time. So, as Geo stated, those who were sold shares at the IPO price paid $38, but then the stock could open at whatever price was the point where bid and ask balanced.   I snapped a screen capture of this chart on the first day of trading, the daily charts aren't archived where I can find them. This is from Yahoo Finance. You can see the $42 open from those who simply wanted in but couldn't wait, the willingness of sellers to grab their profit right back to what they paid, and then another wave of buying, but then a sell-off. It closed virtually unchanged from the IPO price. This all happens at once and quickly. Not in order.  So the HFT floods the exchange with orders. This is independent of anything. They would be doing this no matter what. Simply in anticipation of finding someone who will want what they're trying to buy.   They then notice someone wants what they have a buy order for. They, at the same time, cancel all orders that don't fit this criteria. At the same time, they're testing this guy to see what his price is. So while they're testing this guy they're cancelling all orders that are above his strike price for that stock. They let the right order go through, for a lower price. If they can't get a lower price, they just forget it. However, they probably can because they were in line first. They're buying before this guy and AFTER they know what he wants to pay.    Then, they sell it to him. "Stock price is set to the price with the highest transaction volume at any given time.  The stock price you cited was only valid in the last transaction on a specific stock exchange. As such it is more of an ""historic"" value. Next trade will be done with the next biggest volume. Depending on the incoming bids and asks this could be higher or lower, but you can assume it will not be too far off if there is no crash underway. Simple example stock exchange:" Your order may or may not be executed.  The price of stock can open anywhere.  Often yesterday's close is a good indication of today's open, but with a big event overnight, the open may be somewhere quite different.  You'll have to wait and see like the rest of us.  Also, even if it doesn't execute at the open, the price could vary during the day and it might execute later. The sentiment is because between closing and opening a lot can happen, and between opening and the time your order actually goes through, even more can happen.  An after-hours trade has an extra amount of short-term risk attached; the price of a stock at the opening bell is technically the same as its price as of the closing the previous trading day, but within a tenth of a second, which is forever in a computerized exchange, that price may move drastically one way or the other, based on news and on other markets. The sentiment, therefore, is simple; if you're trading after-hours, you're trading risky. You're not trading based on what the market's actually doing, you're trading based on what you think the market will do in the morning, and there's still more math going on every second in the privately-held supercomputers in rented cubes in the NYSE basement than you could do all night, digesting this news and projecting what it's going to do to the stocks. Now, if you've done your homework and the stock looks like a good long-term buy, with or without any after-hours news, then place the order at 3 in the morning; who cares what the stock's gonna do at the opening bell. You're gonna hold that stock for the next ten years, maybe; what it does in 5 seconds of opening turmoil is relatively minor compared to the monthly trends that you should be worrying about. "What you are saying is a very valid concern.  After the flash crash many institutions in the US replaced ""true market orders"" (where tag 40=1 and has no price) with deep in the money limit orders under the hood, after the CFTC-SEC joint advisory commission raised concerns about the use of market orders in the case of large HFT traders, and concerns on the lack of liquidity that caused market orders that found no limit orders to execute on the other side of the trade, driving the prices of blue chip stocks into the pennies.  We also applaud the CFTC requesting comment regarding whether it is   appropriate to restrict large order execution design that results in   disruptive trading. In particular, we believe there are questions   whether it is ever appropriate to permit large order algorithms that   employ unlimited use of market orders or that permit executions at   prices which are a dramatic percentage below the present market price   without a pause for human review So although you still see a market order on the front end, it is transformed to a very aggressive limit in the back end. However, doing this change manually, by selling at price 0 or buying at 9999 may backfire since it may trigger fat finger checks and prevent your order from reaching the market.  For example BATS Exchange  rejects orders that are priced too aggressively and don't comply with the range of valid prices.  If you want your trade to execute right now and you are willing to take slippage in order to get fast execution, sending a market order is still the best alternative." It depends on how you place your stop order and the type of stop orders available from your broker. If you place a stop market order and the following day the stock opens below your stop your stock will be stopped out at or around the opening price, meaning you can potentially end up with quite a large gap. If you place a stop limit order, say you place your stop at $10.00 with a limit price of $9.90, and if the price opens below $9.90, say at $9.50, your limit sell order of $9.90 will be placed onto the market but it will not be executed until the price goes back up to $9.90 or above. The third option is to place a Guaranteed Stop Loss, and as specified you are guaranteed your stop price even if the price gaps down below your stop price. You will be paying an extra fee for the Guaranteed Stop Loss Order, and they are usually mainly available with CFD Brokers (so if you are in the USA you might be out of luck). Opening - is the price at which the first trade gets executed at the start of the trading day (or trading period). High - is the highest price the stock is traded at during the day (or trading period). Low - is the lowest price the stock is traded at during the day (or trading period). Closing - is the price at which the last trade gets executed at the end of the trading day (or trading period). Volume - is the amount of shares that get traded during the trading day (or trading period). For example, if you bought 1000 shares during the day and another 9 people also bought 1000 shares each, then the trading volume for the day would be 10 x 1000 = 10,000. "For any large company, there's a lot of activity, and if you sell at ""market"" your buy or sell will execute in seconds within a penny or two of the real-time ""market"" price.  I often sell at ""limit"" a few cents above market, and those sell within 20 minutes usually.  For much smaller companies, obviously you are beholden to a buyer also wanting that stock, but those are not on major exchanges.  You never see whose buy order you're selling into, that all happens behind the curtain so to speak." In general, how does a large open market stock sale affect prices? A very general answer, all other things being equal, the price will move down. However there is nothing general. It depends on total number of shares in market and total turn over for that specific shares. The order book for the day etc. What is the maximum percentage of a company you could sell per day before the trading freezes, and what factors matter? Every stock exchange has rules that would determine when a particular stock would be suspended from trading, generally a 10-20% swing [either ways]. Generally highly liquid stock or stock during initial listing are exempt from such limits as they are left to arrive the market price ...  A large sell order may or may not swing the price for it to get suspended. At times even a small order may do ... again it is specific to a particular stock. In general stock markets are very similar to that, however, you can also put in limit orders to say that you will only buy or sell at a given price. These sit in the market for a specified length of time and will be executed when an order arrives that matches the price (or better). Traders who set limit orders are called liquidity (or price) makers as they provide liquidity (i.e. volume to be traded) to be filled later. If there is no counterparty (i.e. buyer to your seller) in the market, a market maker; a large bank or brokerage who is licensed and regulated to do so, will fill your order at some price. That price is based on how much volume (i.e. trading) there is in that stock on average. This is called average daily volume (ADV) and is calculated over varying periods of time; we use ADV30 which is the 30 day average. You can always sell stocks for whatever price you like privately but a market order does not allow you to set your price (you are a price taker) therefore that kind of order will always fill at a market price. As mentioned above limit orders will not fill until the price is hit but will stay on book as long as they aren't filled, expired or cancelled. A stop-loss order becomes a market order when a trade has occurred at or below the trigger price you set when creating the order. This means that you could possibly end up selling some or all of your position at a price lower than your trigger price. For relatively illiquid securities your order may be split into transactions with several buyers at different prices and you could see a significant drop in price between the first part of the order and the last few shares. To mitigate this, brokers also offer a stop-limit order, where you set not only a trigger price, but also a minimum price that you are will to accept for your shares. This reduces the risk of selling at rock bottom prices, especially if you are selling a very large position. However, in the case of a flash crash where other sellers are driving the price below your limit, that part of your order may never execute and you could end up being stuck with a whole lot of shares that are worth less than both your stop loss trigger and limit price. For securities that are liquid and not very volatile, either option is a pretty safe way to cut your losses. For securities that are illiquid and/or very volatile a stop-limit order will prevent you from cashing out at bottom dollar and giving away a bargain to lurkers hanging out at the bottom of the market, but you may end up stuck with shares you don't want for longer than originally planned. It's up to you to decide which kind of risk you prefer. There are a couple of things you could do, but it may depend partly on the type of orders your broker has available to you. Firstly, if you are putting your limit order the night before after close of market at the top of the bids, you may be risking missing out if bid & offer prices increase by the time the market opens the next day. On the other hand, if bid & offer prices fall at the open of the next day you should get your order filled at or below your limit price. Secondly, you could be available at the market open to see if prices are going up or down and then work out the price you want to buy at then and work out the quantity you can buy at that price. I personally don't like this method because you usually get too emotional, start chasing the market if prices start rising, or start regretting buying at a price and prices fall straight afterwards. My preferred method is this third option. If your broker provides stop orders you can use these to both get into and out of the market. How they work when trying to get into the market is that once you have done your analysis and picked a price that you would want to purchase at, you put a stop buy order in. For example, the price closed at $9.90 the previous day and there has been resistance at $10.00, so you would put a stop buy trigger if the price goes over $10, say $10.01. If your stop buy order gets triggered you can have either a buy market order or a limit order above $10.01 (say $10.02). The market order would go through immediately whilst the limit order would only go through if the price continues going to $10.02 or above. The advantage of this is that you don't get emotional trying to buy your securities whilst sitting in front of the screen, you do your analysis and set your prices whilst the market is closed, you only buy when the security is rising (not falling). As your aim is to be in long term you shouldn't be concerned about buying a little bit higher than the previous days close. On the other hand if you try and buy when the price is falling you don't know when it will stop falling. It is better to buy when the price shows signs of rising rather than falling (always follow the trend). "if it opens below my limit order  What exactly are you trying to achieve here? If your limit order is for 100 and the stock opens ""below"" your limit order, say 99, then it is obviously going to buy it automatically.  also place a stop loss on the same order  Most brokers allow limit + stop loss order at the same time on same order.  What I conclude from your question is that you're with a broker that is using obscure technology. Get a better broker or maybe, retry phrasing your question correctly."