Why doesn't buy at open get the official open price?
"There is no official price. There is only the price a seller is willing to offer and a buyer is willing to accept at that moment. It tends to be close to the price negotiated for the last such sale, but that's just market statistics, not anything actively managed or guaranteed. ""Past performance is no guarantee of future results;"" this buyer and seller may not agree with the previous pair. Especially when the market has been closed overnight but real-world events have continued to occur."
Depending on your strategy, it could be though there is also something to be said for what kind of order are you placing: Market, limit or otherwise? Something else to consider is whether or not there is some major news that could cause the stock/ETF to gap at the open.  For example, if a company announces strong earnings then it is possible for the stock to open higher than it did the previous day and so a market order may not to take into account that the stock may jump a bit compared to the previous close.  Limit orders can be useful to put a cap on how much you'll pay for a stock though the key would be to factor this into your strategy of when do you buy. If the share is listed on a stock exchange that creates liquidity and orderly sales with specialist market makers, such as the NYSE, there will always be a counterparty to trade with, though they will let the price rise or fall to meet other open interest.  On other exchanges, or in closely held or private equity scenarios, this is not necessarily the case (NASDAQ has market maker firms that maintain the bid-ask spread and can do the same thing with their own inventory as the specialists, but are not required to by the brokerage rules as the NYSE brokers are).  The NYSE has listing requirements of at least 1.1 million shares, so there will not be a case with only 100 shares on this exchange. If you're talking about an ETF trading on Arca, it's probably because of the opening auction: The match price is the price that maximizes the volume that can be executed within the Auction Collars. The Core Open Auction will use the match price closest to the closing price of the previous trading day (based on normal market hours) if more than one indicative match price is valid. The core opening auction doesn't really take the opening session activity into account, as you can see - the market runs an auction and whatever price clears the most volume, within certain limits, is the opening print. "Most of the time* you're selling to other investors, not back to the company. The stock market is a collection of bid (buy offers) and asks (sell offers). When you sell your stock as a retail investor at the ""market"" price you're essentially just meeting whatever standing bid offers are on the market.  For very liquid stocks (e.g. Apple), you can pretty much always get the displayed price because so many stocks are being traded. However during periods of very high volatility or for low-volume stocks, the quoted price may not be indicative of what you actually pay.  As an example, let's say you have 5 stocks you're trying to sell and the bid-side order book is 2 stocks for $105, 2 for $100, and 5 for $95. In this scenario the quoted price will be $105 (the best bid price), but if you accept market price you'll settle 2 for 105, 2 for 100, and 1 for 95. After your sell order goes through, the new quoted price will be $95. For high volume stocks, there will usually be so many orders near the midpoint price ($105, in this case) that you won't see any price slippage for small orders.  You can also post limit orders, which are essentially open orders waiting to be filled like in the above example. They ensure you get the price you want, but you have no way to guarantee they'll be filled or not.  Edit: as a cool example, check out the bitcoin GDAX on coinbase for a live example of what the order book looks like for stocks. You'll see that the price of bitcoin will drift towards whichever direction has the less dense order book (e.g. price drifts upwards when there are far more bids than asks.)" I assume you're talking about a sell order, not a buy order. When you place a limit sell order, your order is guaranteed to be placed at that price or higher.  If the market is currently trading much higher than the price of your sell order, then your mistakenly low limit order will be essentially a market order, and will be filled at  the current bid price. So the only way this is a problem is if you want to place a limit sell that is much higher than the current market, but mistakenly place a limit lower than the current market. "Stocks prices are determined whenever a buyer and seller agree to trade at a given price. The company (you use AAPL as an example) doesn't set its own stock price. Rather, the investors set the price every time it trades. There's no ""official"" price -- just the last trade. Likewise, you can offer to trade a stock at whatever price you want: that's the definition of a limit order. You might not find a willing buyer or seller at that price, but you can certainly open an order. Stock quotes that you get from your broker or a finance web site reflect the price as last traded. These quotes are updated throughout the trading day and the frequency and delay varies amongst quote providers. Like Knuckle-Dragger suggests in the comments, there are ways to get real-time quotes. It's often more helpful to think in terms of bid/ask instead of ""official price"". See this question for details." I think the best answer that doesn't make the buyer look like a moron is this. Buyer had previously sold a covered call.  They wanted to act on a different opportunity so they did a closing buy/write with a spread of a couple cents below asking for the stock, but it dipped a couple cents and the purchase of those options to close resolved at 4 cents due to lack of sellers. In general a stock can open at absolutely any price with no regard for the closing price or after hours price the previous day. The opening price will be determined by the best bid and offer made by people who decide to trade the next day.  Some of the those people may have put orders in on a prior day that are still on the books and matter, but there's a lot of time overnight for people to cancel orders and enter new ones, which is especially likely to happen if there was substantive news overnight. As for what you can do in your case, you have the same options that you always had:  Sell or hold.  If you're selling, you can sell after hours, in the pre-open hours, or during the trading day.  There's nothing we can say about this case that's really any different than we can say about any other stock on any other day. You're assuming options traded on the open market. To close open positions, a seller buys them back on the open market. If there's little on offer, this will drive the price up. 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. The simple answer: The opening price is the price of the first trade of the day and the closing price is the price of the last trade of the day.  And since the stock price change from trade to trade they are usually different. The price gaps up because the offer is for a price above the current price. Therefore people want to buy now before the price jumps to the offer level. Of course it does depend on the tone of the announcement,  which party is making the announcement, and are they announcing an offer or a deal. If the price is $10, and the offer is for $12; then the price may quickly jump. The early buyers will make the most quick money. They hope that the deal is done quickly, or if not the final price ends up higher.  There are risks. The company could reject the offer. The due diligence could expose a problem. The regulators could reject the deal based on anti-trust issues. The deal could take many months to complete. Or the final deal could be for shares in the new company.  The risks are one reason people sell after the deal/offer is announced. In other cases the seller finally is seeing a profit, or a smaller loss and wants out while they can. "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." "Prices reflect all available information. (Efficient markets hypothesis) A lot can happen between the time a stock closes on one day and opens on another. Particularly in a heavily traded stock such as IBM. Basically, you have a different ""information set"" the following day, which implies a different price. The instances where you are most likely to have a stock where the price opens at the same price is at the previous close is a thinly traded stock on which you have little information, meaning that the ""information set"" changes less from day to day." "Some technical indicators (e.g. Williams %R) indicate whether the market is overbought or oversold.   ... Every time a stock or commodity is bought, it is also sold. And vice versa. So how can anything ever be over-bought or over-sold? But I'm sure I'm missing something. What is it? You're thinking of this as a normal purchase, but that's not really how equity markets operate. First, just because there are shares of stock purchased, it doesn't mean that there was real investor buyer and seller demand for that instrument (at that point in time).  Markets have dedicated middlemen called Market Makers, who are responsible to make sure that there is always someone to buy or sell; this ensures that all instruments have sufficient liquidity.  Market Makers may decide to lower their bid on a stock based on a high number of sellers, or raise their ask for a high number of buyers. During an investor rush to buy or sell an instrument (perhaps in response to a news release), it's possible for Market Makers to accumulate a large number of shares, without end-investors being involved on both sides of the transaction.  This is one example of how instruments can be over-bought or over-sold. Since Williams %R creates over-bought and over-sold signals based on historical averages of open / close prices, perhaps it's better to think of these terms as ""over-valued"" and ""under-valued"".  Of course, there could be good reason for instruments to open or close outside their expected ranges, so Williams %R is just a tool to give you clues... not a real evaluation of the instrument's true value."