What is an “at close order” in the stock market?
Usually backtests for (long-term) strategies are evaluated on a end-of-day basis where you only consider close prices. If your strategy performs well in these backtests, hopes are that if you use a market-on-close (MOC) order your performance will not diverge too much from the backtest. The fact that it won't diverge much is important if you keep backtesting the strategy along with the real trading to see regime changes or similar.  If you used end-of-day prices for the backtests but some arbitrary intraday market order, you'd have some difficulties to explain deviations between the two. What it is:  MOC orders can be submitted during the day, but they won't be executed until shortly before the market (or more precise the current session) closes. Investopedia defines it in the following way: It's essentially a market order that doesn't get entered until the last minute (or thereabouts) of trading. With this type of order you are not necessarily guaranteed the closing price but usually something very similar, depending on the liquidity in the market and bid-ask for the security in question. Traders who believe that a security or market will move more heavily during the last few minutes of trading will often place such an order in the hopes of having their order filled at a more desirable price.
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. "A market sell order will be filled at the highest current ""bid"" price. For a reasonably liquid stock, there will be several buy orders in line, and the highest bid must be filled first, so there should a very short time between when you place the order and when it is filled.   What could happen is what's called front running. That's when the broker places their own order in front of yours to fulfill the current bid, selling their own stock at the slightly higher price, causing your sale to be filled at a lower price.  This is not only unethical but illegal as well. It is not something you should be concerned about with a large broker.   You should only place a market order when you don't care about minute differences between the current ask and your execution price, but want to guarantee order execution. If you absolutely have to sell at a minimum price, then a limit order is more appropriate, but you run the risk that your limit will not be reached and your order will not be filled. So the risk is a tradeoff between a guaranteed price and a guaranteed execution." "That's the way the markets work in THEORY. In actual fact, markets are subject to ""real world"" pressures. That is, there are so many things going on in the market that the end of the ""Lined In"" lock up is just one of many. To produce the result you describe, traders would have to hold cash in reserve for this so-called ""contingency"" to buy at the end of the lock-up. In most cases, they wouldn't want to because of everything else that is going on.  To use a real world analogy, would you want to wait until the last possible moment before going to the bathroom? Or would you go now while you had the chance? That's what the decision about ""holding cash in reserve for a contingency"" is like." 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. "The SEC regulation on insider trading is ""engage in the purchase and sale of any security on the basis of material non public information"".  The case I remember off the top of my head is Kodak developing an instant photo camera in the 1970s, and about 4 months before Kodak made this knowledge public, the CBOE had to close options trading on Polaroid because they had an excessive buildup of uncovered short positions." 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. 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. The Limit Order are matched based on amount and time. The orders are listed Highest to Lowest on the Buy Side. The orders are listed Lowest to Highest on the Sell Side. If there are 2 Sell orders for same amount the order which is first in time [fractions of milliseconds] is first.  The about is the example as to how the orders would look like on any exchange.  Now the highest price the buyer is ready to pay is 20.21 and the lowest price a seller is ready to sell for is 20.25. Hence there is no trade. Now if a new Buy order comes in at 20.25, it matches with the sell and the deal is made. If a new Buy order comes in at 20.30, it still matches at 20.25. Similarly if a Sell order come in at 20.21, it matches and a deal is made. If a Sell order come in at 20.11, it still matches 20.21.   Incase of market order, with the above example if there is a Buy order, it would match with the lowest sell order at 20.25, if there is not enough quantity , it would match the remaining quantity to the next highest at 20.31 and continue down. Similarly if there is a Sell market order, the it would match to the maximum a seller is ready to buy, ie 20.21, if there is not sufficient buy quantity at 20.21, it will match with next for 20.19   If say there are new buy order at 20.22 and sell orders at 20.24, these will sit first the the above queue to be matched. In your above example the Lowest Sell order was at 20.10 at time t1 and hence any buy order after time t1 for amount 20.10 or greater would match to this and the price would be 20.10. However if the Buy order was first ie at t1 there was a buy order for 20.21 and then at time later than t1, there is a sell order for say 20.10 [amount less than or equal to 20.21] it would match for 20.21. Essentially the market looks at who was the first to sell at lower price or who was the first to buy at higher price and then decide the trade.  Edit [To Clarify xyz]: Say if there is an Sell order at $10 Qty 100. There is a buyer who is willing to pay Max $20 and is looking for Qty 500. Your key assumption that the Buyer does not know the current SELL price of $10 is incorrect. Now there are multiple things, the Buyer knows the lowest Sell order is at $10, he can put a matching Buy order at $10 Qty 100, and say $11 Qty 100 etc. This is painful. Second, lets say he puts a Buy order at $10 Qty 100, by the time the order hits the system someone else has put the trade at $10 and his order is fulfilled. So this buyer has to keep looking at booking and keep making adjustments, if its a large order, it would be extremely difficult and frustrating for this Buyer. Hence the logic of giving preference. The later Buy order says ... The Max I can pay is $20, match eveything at the current price and get the required shares. "My broker offers the following types of sell orders: I have a strategy to sell-half of my position once the accrued value has doubled.  I take into account market price, dividends, and taxes (Both LTgain and taxes on dividends).  Once the market price exceeds the magic trigger price by 10%, I enter a ""trailing stop %"" order at 10%.  Ideally what happens is that the stock keeps going up, and the trailing stop % keeps following it, and that goes on long enough that accrued dividends end up paying for the stock.  What happens in reality is that the stock goes up some, goes down some, then the order gets cancelled because the company announces dividends or something dumb like that. THEN I get into trouble trying to figure out how to re-enter the order, maintaining the unrealized gain in the history of the trailing stop order.  I screwed up and entered the wrong type of order once and sold stock I didn't want to. Lets look at an example. a number of years ago, I bought some JNJ -- a hundred shares at 62.18.  - Accumulated dividends are 2127.75  - My spreadsheet tells me the ""double price"" is 104.54, and double + 10% is 116.16.  - So a while ago, JNJ exceeded 118.23, and I entered a Trailing Stop 10% order to sell 50 shares of JNJ.  The activation price was 106.41.  - since then, the price has gone up and down...  it reached a high of 126.07, setting the activation price at 113.45.  - Then, JNJ announced a dividend, and my broker cancelled the trailing stop order.  I've re-entered a ""Stop market"" order at 113.45.  I've also entered an alert for $126.07 -- if the alert gets triggered, I'll cancel the Market Stop and enter a new trailing stop." "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.)" "Limited Price is probably equivalent to the current par value of a ""limit order"". Markets move fast, and if the commodity is seeing some volatility in the buy and sell prices, if you place an ordinary buy order you may not get the price you were quoted. A ""limit order"" tells your broker or whomever or whatever is making the order on your behalf that you will pay no more than X yuan. While the market is below that price, the trader will attempt to get you the quantity you want, but if they can't get you your full order for an average price less than the limit, the whole thing is rolled back. You can set a limit at any price, but a limit order of 1 yuan for a pound of sterling silver will likely never be executed as long as the market itself is functioning. So, you are being provided with a ""par value"" that they can guarantee will be executed in the current market. Entrustment prices are probably prices offered to the managers of trust funds. A trust is simply a set of securities and/or cash which is placed under the nominal control of a third party, who then must in good faith attempt to fulfill the goals of the actual owner of the securities with regards to growth or retention of value. Trustees almost never speculate with the money they control, but when they do move money it's often a sizeble chunk (hundreds of thousands or millions of dollars instead of a few thousand dollars here and there). So, in return for the long-term holdings, large buys and sells, and thus the reduced cost of maintaining a business relationship with the broker, the broker may offer better prices to trust fund managers." "During the day, market and limit orders are submitted at any time by market participants and there is a bid and an ask that move around over time.  Trades occur whenever a market order is submitted or a limit order is submitted that at a price that matches or exceeds an existing limit order.  If you submit a market order, it may consume all best-price limit orders and you can get multiple prices, changing the bid or ask at the same time.  All that stuff happens during the trading day only. What happens at the end of the day is different.  A bunch of orders that were submitted during the day but marked as ""on close"" are aggregated with any outstanding limit orders to create a single closing price according to the algorithm established by the exchange.  Each exchange may handle the details of this closing event differently.  For example, the Nasdaq's closing cross or the NYSE's closing auction. The close is the most liquid time of the day, so investors who are trading large amounts and not interested in intraday swings will often submit a market-on-close or limit-on-close order.  This minimizes their chance of affecting the price or crossing a big spread.  It's actually most relevant for smaller stocks, which may have too little volume during the day to make big trades, but have plenty at the close.  In short, the volume you see is due to these on-close orders. The spike in volume most likely has no special information about what will happen overnight or the next day.  It's probably just a normal part of the market for illiquid stocks." Close-end funds just means there's a fixed number of shares available, so if you want to buy some you must purchase from other existing owners, typically through an exchange. Open-end funds mean the company providing the shares is still selling them, so you can buy them directly from the company.  Some can also be traded on exchanges as well. "The ""price"" is the price of the last transaction that actually took place. According to Motley Fool wiki: A stock price is determined by what was last paid for it. During market hours (usually weekdays from 9:30AM-4:00PM eastern), a heavily traded issue will see its price change several times per second. A stock's price is, for many purposes, considered unchanged outside of market hours. Roughly speaking, a transaction is executed when an offer to buy matches an offer to sell. These offers are listed in the Order Book for a stock (Example: GOOG at Yahoo Finance).  This is actively updated during trading hours. This lists all the currently active buy (""bid"") and sell (""ask"") orders for a stock, and looks like this:  You'll notice that the stock price (again, the last sale price) will (usually*) be between the highest bid and the lowest ask price. * Exception: When all the buy or sell prices have moved down or up, but no trades have executed yet." "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.)"