Can a broker refuse to place my limit-orders?
Ethereum trades are not subject to the same rules as securities are. Thats the primary flaw in your assessment. Yes, cryptocurrency is a free trading arena where you can actually take advantage of market inefficiencies yourself 24 hours a day, 7 days a week, at massive profits. The equity securities markets are not like that, and can't be used as a comparison. If you have a preference for flexibility, then it is already clear which markets work better for you. Market makers can make stub quotes, brokers can easily block their retail customers from doing it themselves. Even the dubious market manipulation excuse is reference to a sanction exclusive to the equity markets. The idea that it went through a week earlier probably triggered the compliance review. Yes, a broker can refuse to place your limit order.
"I think for this a picture is worth a thousand words.  This is a ""depth chart"" that I pulled from google images, specifically because it doesn't name any security.  On the left you have all of the ""bids"" to buy this security, on the right you have the ""asks"" to sell the security.  In the middle you have the bid/ask spread, this is the space between the highest bid and the lowest ask.  As you can see you are free to place you order to the market to buy for 232, and someone else is free to place their order to the market to sell for 234.  When the bid and the ask match there's a transaction for the maximum number of available shares.  Alternatively, someone can place a market order to buy or sell and they'll just take the current market price. Retail investors don't really get access to this kind of chart from their brokers because for the most part the information isn't terribly relevant at the retail level." "I've alway thought that it was strange, but the ""price"" that gets quoted on a stock exchange is just the price of the last transaction. The irony of this definition of price is that there may not actually be any more shares available on the market at that price. It's also strange to me that the price isn't adjusted at all for the size of the transaction. A transaction of just 1 share will post a new price even if just seconds earlier 100,000 shares traded for a different price. (Ok, unrealistic example, but you get my point.) I've always believed this is an odd way to describe the price. Anyway, my diatribe here is supposed to illustrate the point that the fluctuations you see in price don't really reflect changing valuations by the stock-owning public. Each post in the exchange maintains a book of orders, with unmatched buy orders on one side and unmatched sell orders on the other side. If you go to your broker and tell him, ""fill my order for 50,000 shares at market price"", then the broker won't fill you 50,000 shares at .20. Instead, he'll buy the 50 @ .22, then 80 @ .23, then 100 @ .30, etc. Because your order is so large compared to the unmatched orders, your market order will get matched a bunch of the unmatched orders on the sell side, and each match will notch the posted price up a bit. If instead you asked the broker, ""open a limit order to buy 50000 shares at .20"", then the exchange will add your order to the book: In this case, your order likely won't get filled at all, since nobody at the moment wants to sell at .20 and historically speaking it's unlikely that such a seller will suddenly appear. Filling large orders is actually a common problem for institutional investors: http://www.businessweek.com/magazine/content/05_16/b3929113_mz020.htm http://www.cis.upenn.edu/~mkearns/papers/vwap.pdf (Written by a professor I had in school!)" "Always use limit orders never market orders. Period. Do that and you will always pay what you said you would when the transaction goes through. Whichever broker you use is not going to ""negotiate"" for the best price on your trade if you choose a market order.  Their job is to fill that order so they will always buy it for more than market and sell it for less to ensure the order goes through. It is not even a factor when choosing between TradeKing and Scottrade. I use Trade King and my friend uses ScottTrade.  Besides the transaction fee (TK is a few $$ cheaper), the only other things to consider are the tools and research (and customer service if you need it) that each site offers. I went with TK and the lower transaction fee since tools and research can be had from other sources. I basically only use it when I want to make a trade since I don't find the tools particularly useful and I never take an analyst's opinion of a stock at face value anyway since everybody always has their own agenda." "I place a trade, a limit order on a thinly traded stock. I want to buy 1000 shares at $10. The current price is $10.50. Someone places a market order for 500 shares. Another trader has a limit order for $10.10 for 400 shares. His order fills, and I get 100 at my price. I wait another day to see if I get any more shares. This is just an example of how it can work. I can place my order as ""all or none"" if I wish to avoid this." Is this due to the delay?  Yes, but the delay is caused by your broker and its affiliates.  Trailing Stop Order is not exchange native, meaning that the broker is responsible for keeping track of whether the stop price has been reached, and the broker is responsible for sending the subsequent Market Order to the exchange.  For certain exchange, even Stop Order or Stop Limit Order is not exchange native.  Is it common to be so different? No, only in times of extreme volatility. To answer your question in its entirety there's more information we need (exchange, session, traded security, order type, etc.). Most exchanges support partial fills, that is your order will be partially executed and modified.  In your example, you'd get an execution of 10 shares at $100, and your order ticket will be modified to $100 for 990 shares. Like John Bensin explained, there are ways to prevent partial filling through order modifiers (e.g. Fill-or-Kill). My addition here is, there are also ways to prevent the other bit, i.e. do the partial fill but don't keep a modified order in the system.  You'd have to mark the order Immediate-or-Cancel (IoC).  In your case you'd be partially filled (10 @$100) and that's it.  For the remaining 990 shares you'd have to enter a new order. 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. "Yes.  I heard back from a couple brokerages that gave detailed responses. Specifically: In a Margin account, there are no SEC trade settlement rules, which means there is no risk of any free ride violations. The SEC has a FAQ page on free-riding, which states that it applies specifically to cash accounts. This led me to dig up the text on Regulation T which gives the ""free-riding"" rule in §220.8(c), which is titled ""90 day freeze"". §220.8 is the section on cash accounts. Nothing in the sections on margin accounts mentions such a settlement restriction. From the Wikipedia page on Free Riding, the margin agreement implicitly covers settlement. ""Buying Power"" doesn't seem to be a Regulation T thing, but it's something that the brokerages that I've seen use to state how much purchasing power a client has. Given the response from the brokerage, above, and my reading of Regulation T and the relevant Wikipedia page, proceeds from the sale of any security in a margin account are available immediately for reinvestment. Settlement is covered implicitly by margin; i.e. it doesn't detract from buying power. Additionally, I have personally been making these types of trades over the last year. In a sub-$25K margin account, proceeds are immediately available. The only thing I still have to look out for is running into the day-trading rules."