Why can't I open multiple sell orders?
From the message you report, it sounds like you are trying to sell the same shares twice, you have two open sell orders for the same shares. Either you have accidentally entered two sell orders, or the web site is having a technical problem. I'm not a customer of Fidelity so I can't say what their web site looks like, but there should be some screen that shows your open orders. If looking there doesn't resolve the issue, call customer service.
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. As others have stated, the current price is simply the last price at which the security traded. For any given tick, however, there are many bid-ask prices because securities can trade on multiple exchanges and between many agents on a single exchange. This is true for both types of exchanges that Chris mentioned in his answer. Chris' answer is pretty thorough in explaining how the two types of exchanges work, so I'll just add some minor details. In exchanges like NASDAQ, there are multiple market makers for most relatively liquid securities, which theoretically introduces competition between them and therefore lowers the bid-ask spreads that traders face. Although this results in the market makers earning less compensation for their risk, they hope to make up the difference by making the market for highly liquid securities. This could also result in your order filling, in pieces, at several different prices if your brokerage firm fills it through multiple market makers. Of course, if you place your order on an exchange where an electronic system fills it (the other type of exchange that Chris mentioned), this could happen anyway.  In short, if you place a market order for 1000 shares, it could be filled at several different prices, depending on volume, multiple bid-ask prices, etc. If you place a sizable order, your broker may fill it in pieces regardless to prevent you from moving the market. This is rarely a problem for small-time investors trading securities with high volumes, but for investors with higher capital like institutional investors, mutual funds, etc. who place large orders relative to the average volume, this could conceivably be a burden, both in the price difference across time as the order is placed and the increased bookkeeping it demands.  This is tangentially related, so I'll add it anyway. In cases like the one described above, all-or-none (AON) orders are one solution; these are orders that instruct the broker to only execute the order if it can be filled in a single transaction. Most brokers offer these, but there are some caveats that apply to them specifically. (I haven't been able to find some of this information, so some of this is from memory).  All-or-none orders are only an option if the order is for more than a certain numbers of shares. I think the minimum size is 300 or 400 shares.  Your order won't be placed until your broker places all other orders ahead of it that don't have special conditions attached to them.  I believe all-or-none orders are day orders, which means that if there wasn't enough supply to fill the order during the day, the order is cancelled at market close.  AON orders only apply to limit orders. If you want to replicate the behavior of a market order with AON characteristics, you can try setting a limit buy/sell order a few cents above/below the current market price. "You can place the orders like you suggested.  This would be useful in a market that is moving quickly where you want to be reasonably sure of execution but don't want the full exposure of a market order.  This won't jump your spot in the queue though in the sense that you won't get ahead of other orders that are ""ready"" for execution just because you have crossed the spread aggressively." I'm talking about day trading here. Automated day trading never worked for me. But I will also admit I am terrible at automated day trading. I'm sorry if the premise of my post sounds off. I know it sounds like I'm being an idiot by not going the automated route, but it works for me and that's why I'm going to stick with my own techniques. Why change it if it's working? Buy and sell orders always include the price at which you buy/sell. That's how the market prices for stocks are determines. So if you want to place a buy order at 106, you can do that. When that order was fulfilled and you have the stock, you can place a sell order at 107. It will be processed as soon as someone places a buy order at 107. Theoretically you can even place sell orders for stocks you haven't even bought yet. That's called short selling. You do that when you expect a stock to go down in the future. But this is a very risky operation, because when you mispredict the market you might end up owing more money than you invested. No responsible banker will even discuss this with you when you can not prove you know what you are doing. Sounds to me like you're describing just how it should work.  Ask is at 30, Bid is at 20; you offer a new bid at 25.  Either: Depending on liquidity, one or the other may be more likely. This Investorplace article on the subject describes what you're seeing, and recommends the strategy you're describing precisely. Instead of a market order, take advantage of the fact that the options world truly is a marketplace — one where you can possibly get a better price just by asking. How does that work? If you use a limit order (instead of a market order) when opening a position, you can tell your broker how much you are willing to pay to enter a trade. For example, if you enter a limit price of $1.15, you can see whether the market-maker will bite. You will be surprised at how many times you will get your price (i.e., $1.15) instead of the ask price of $1.30. If your order at $1.15 is not filled after a few minutes, you can modify your order and pay the ask price by entering a market order or limit order at the ask price (that is, you can tell your broker to pay no more than $1.30). No you can't, as you would have to have a different order for each security. Usually the bigger the order the more the brokerage you would also pay. "Yes there is, it is called a One-Cancels-the-Other Order (OCO). Investopedia defines a OCO order as: Definition of 'One-Cancels-the-Other Order - OCO' A pair of orders stipulating that if one order is executed, then the   other order is automatically canceled. A one-cancels-the-other order   (OCO) combines a stop order with a limit order on an automated trading   platform. When either the stop or limit level is reached and the order   executed, the other order will be automatically canceled. Seasoned   traders use OCO orders to mitigate risk. I use CMC Markets in Australia, and they allow free conditional and OCO 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 next two conditional orders form part of the OCO Orders. 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 30%, that is if the price reached $13.00. So you would type in 13.00 in the box after ""If at or above ?"" and again select if you want a limit or market order. Once you have bought the stock if the stop order gets triggered then the take profit order gets cancelled automatically. If on the other hand the take profit order gets triggered then the stop loss order gets cancelled automatically. These OCO conditional orders can be placed either at the time you enter your buy order or after you have already bought the stock, and they can be edited or deleted at any time. The broker you use may have a different process for entering conditional and OCO orders such as these." I'd say yes, and hope that my anecdotal evidence serves as proof. My IRA is not a margin account. It can't be.  I attempt to create a covered call, buying a stock at say $20, and selling a call for $4, for net $16 cost. The account only had $1610 at the time, and the trades go through just fine. Yes, I needed to enter as a limit order, at the same time, a single order with the $16 debit limit.  If this is not enough proof, I'd be curious - why not? The option proceeds must clear, of course, which it does. 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: A stock is only worth what someone is willing to pay for it. If it trades different values on different days, that means someone was willing to pay a higher price OR someone was willing to sell at a lower price.  There is no rule to prevent a stock from trading at $10 and then $100 the very next trade... or $1 the very next trade. (Though exchanges or regulators may halt trading, cancel trades, or impose limits on large price movements as they deem necessary, but this is beside the point I'm trying to illustrate). Asking what happens from the close of one day to the open of the next is like asking what happens from one trade to the next trade... someone simply decided to sell or pay a different price.  Nothing needs to have happened in between. Set a good till cancel GTC order, and partial fills will just roll over to the market session if it doesn't fill completely during the first market session It is a very low probability that each share will only be taken one at a time. It isn't a low probability that it will fill in two or three orders, but this is all a factor of how liquid the stocks you bought are. Also your limit order price is also a factor in this "I assert that it's simply not possible for them to place an order that gets ahead of yours (the first step in ""sell it back to you at a higher price""). They only know your order was placed after it reaches the exchange and gets filled." TD will only sell the stock for you if there's a buyer. There was a buyer, for at least one transaction of at least one stock at 96.66. But who said there were more? Obviously, the stocks later fell, i.e.: there were not that many buyers as there were sellers. What I'm saying is that once the stock passed/reached the limit, the order becomes an active order. But it doesn't become the only active order. It is added to the list, and to the bottom of that list. Obviously, in this case, there were not enough buyers to go through the whole list and get to your order, and since it was a limit order - it would only execute with the limit price you put. Once the price went down you got out of luck.  That said, there could of course be a possibility of a system failure. But given the story of the market behavior - it just looks like you miscalculated and lost on a bet. "First, as @littleadv mentions, and as I've pointed out before, anyone who participates in a market using limit orders (which, by the way, should be every non-professional investor) is by definition a market maker.  So, I will assume that your question pertains both to official market makers and to ""retail investors"" using limit orders. When you remark that there are such ""tight spreads"" in ""liquid assets"", what you are really saying is ""wow, look at all the market makers in these products!""  That's the benefit of electronic trading and algorithmic traders -- millions of participants each with their own opinion of the value of a financial instrument, trying to find people who have very specifically opposing opinions of the value of that same instrument.  This is called price discovery, and is the entire point of financial markets. So, you ask why are there all these market makers present to create such tight spreads in assets like SPY?  Answer: Because they can make money in these markets: Imagine (towards a contradiction) that market makers thought they couldn't make money by offering tight spreads in SPY, and so SPY had a wider spread than it actually does.  For example, say the highest bid for SPY was $99.98 and the lowest ask was $100.01.  Now imagine that a market maker with perfect knowledge of the future came along knowing that he would be able to sell SPY for $100.01 in 5 minutes.  Then he would load up as many buy orders as he could for $100.00 or lower.  (He wouldn't bid $100.01 or higher because those trades would not be profitable according to his information -- at least not 5 minutes from now.)  So the spread had previously been $0.03 and then suddenly it was $0.01, all because a market maker with better information came along and realized he could make money by creating a tighter market! Now, nobody has perfect knowledge of the future, which is why markets are never infinitely tight or infinitely liquid.  Each market maker has to weigh possible profits against the probability that those profits will actually turn into losses.  But if one market maker decides not to participate in a particular instrument, there's bound to be another market maker who will happily take his place.  So the very fact that there are so many market participants with resting buy/sell orders for SPY right now is proof that there are market makers able to make money doing so.  If they could not make money, they wouldn't be there, and the spread would be wider. 10-15 years ago, before electronic trading and algorithmic trading, the number of market participants was far lower, and the spreads were far wider, meaning retail investors like you and me had a much harder time making money.  The only people making money were the institutional investors, the brokers, and the exchanges.  Now that all these new millions of players are present in the market, retail investors like you and me get to participate and make money too."