Are limit orders safe?
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. Limit orders are generally safer than market orders. Market orders take whatever most-favorable price is being offered. This can be especially dangerous in highly volatile stocks which have a significant spread between the bid and ask. That being said, you want to be very careful that you enter the price you intend into a limit order. It is better to be a bit slower at entering your orders than it is to make a terrible mistake like the one you mention in your question.
"The SEC reference document (PDF) explains order types in more detail. A fill-or-kill order is neither a market order nor a limit order; instead it's something in between. A market order asks to be filled at the best available price, whatever that price might be when the order gets to the exchange.  Additionally, if there are not enough counterparties to fill the order at the best available price, then part of the order may be filled at a worse price.  This all happens more or less immediately; there's no way to cancel it once it has been placed. A limit order asks to be filled at a particular price, and if no counterparties want to trade at that price right now, then the order will just sit around all day waiting for someone to agree on the price; it can be canceled at any time. A fill-or-kill order asks to be filled at a particular price (like a limit order), but if that price or a better one is not currently available then the order is immediately canceled.  It does not accept a worse price (the way a market order does), nor does it sit around waiting (the way a limit order does).  Since the exchange computes whether to ""fill"" or ""kill"" the order as soon as it is arrives, there's also no way to cancel it (like a market order)." "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." 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. The Key aspect is the risk of market orders;   You should be worried about point 2 & 3 when you are doing market orders. From the non-authoritative Investopedia page: A stop-limit order will be executed at a specified price, or better, after a given stop price has been reached. Once the stop price is reached, the stop-limit order becomes a limit order to buy or sell at the limit price or better. So once the stop price has been breached, your limit order is placed and will be on the order books as a $9 ask. For a vanilla stop order, a market order will be placed and will be filled using the highest active bid(s). "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." From your question, I am guessing that you are intending to have stoploss buy order. is the stoploss order is also a buy order ?  As you also said, you seems to limit your losses, I am again guessing that you have short position of the stock, to which you are intending to place a buy limit order and buy stoploss order (stoploss helps when when the price tanks). And also I sense that you intend to place buy limit order at the price below the market price. is that the situation?  If you place two independent orders (one limit buy and one stoploss buy). Please remember that there will be situation where two orders also get executed due to market movements. Add more details to the questions. it helps to understand the situation and others can provide a strategic solution. The Bank Secrecy Act of 1970 requires that banks assist the U.S. Gov't in identifying and preventing money laundering. This means they're required to keep records of cash transactions of Negotiable Instruments, and report any such transactions with a daily aggregate limit of a value greater than (or equal to?) $10,000. Because of this, the business which is issuing the money order is also required to record this transaction to report it to the bank, who then holds the records in case FinCEN wants to review the transactions. EDITED: Added clarification on the $10,000 rule If you want your order to go through no matter what then you should be using market orders rather than limit orders. With limit orders you may get the price you are after or better but you are not guaranteed to get your order transacted. With a market order you are guaranteed to get you order transacted but may get a price inferior to what you were after. Most times this should only be a few cents but can get much larger in a fast moving or less liquid market. You should incorporate this slippage into your trading plan. Maybe a better option for you, if you are looking at + or - 0.5% from the last price, would be to use conditional triggers (stop buy and sell orders) with your market orders. Once the market moves in your direction your conditional order will be triggered and the stock will be bought at current market price. You could always maintain a limit order to sell at a price you're comfortable with. "Yes, in my humble opinion, it can be ""safe"" to assume that — but not in the sense that your assumption is necessarily or likely correct. Rather, it can be ""safe"" in the respect that assuming the worst — even if wrong! — could save you from a likely painful and unsuccessful speculation in the highly volatile stock of a tiny company with no revenue, no profits, next to no assets, and continued challenges to its existence: ""There is material uncertainty about whether the Company will be able to obtain the required financing. This material uncertainty casts   significant doubt about the Company’s ability to continue as a going   concern."" As a penny stock, they are in good company. Still, there are a variety of other reasons why such a stock might have gone up, or down, and no one [here] can say for sure. Even if there was a news item, any price reaction to news could just amount to speculation on the part of others having enough money to move the stock. There are better investments out there, and cheaper thrills, than most penny stocks." 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). It depends on the sequence in which the order [bid and ask] were placed. Please read the below question to understand how the order are matched. How do exchanges match limit orders? "Yes this is possible in the most liquid securities, but currently it would take several days to get filled in one contract at that amount There are also position size limits (set by the OCC and other Self Regulatory Organizations) that attempt to prevent people from cornering a market through the options market. (getting loads of contacts without effecting the price of the underlying asset, exercising those contracts and suddenly owning a huge stake of the asset and nobody saw it coming - although this is still VERY VERY possible) So for your example of an option of $1.00 per contract, then the position size limits would have prevented 100 million of those being opened (by one person/account that is). Realistically, you would spread out your orders amongst several options strike prices and expiration dates. Stock Indexes are some very liquid examples, so for the Standard & Poors you can open options contracts on the SPY ETF, as well as the S&P 500 futures, as well as many other S&P 500 products that only trade options and do not have the ability to be traded as the underlying shares. And there is also the saying ""liquidity begets liquidity"", meaning that because you are making the market more liquid, other large market participants will also see the liquidity and want to participate, where they previously thought it was too illiquid and impossible to close a large position quickly" This is rather simple if you understand a trailing limit order but to be sure I am going to explain a limit, trailing limit, and trailing LIT order. I am going to use an example assuming that you already own a stock and want to sell it. Limit Order I place an order to sell 100 PG @ 65.00. This order will only be executed if the bid price of PG is at $65.0000 or greater. Trailing Limit Order I place an order to sell 100 CAT @ 85.25 with a trailing 5%. This order will be executed when CAT drops 5% below the highest point it reaches after you place this order. So if you place this order at 85.25 and the stock drops 5% to $80.9875, your order will be executed. However, if the stock jumps to $98, the order will not be executed until the stock falls to $93.10. The sell point will go up with the stock and will always remain at the specified % or $ amount behind the high point. Trailing Limit If Touched Order I place an order to sell 100 INTC @ 24.75 with a trailing 5% if the stock touches $25.00. Essentially, this is the same as the trailing limit except that it doesn't take effect until the stock first gets $25.00.  I think the page they provide to explain this is confusing because I think they are explaining it from the shorting a stock perspective instead of the selling a stock you want to profit from. I could also be wrong in how I understand it. My advice would be to either call their customer support and ask for a better explanation or what I do in my finances, avoid things I don't understand.