Can a retail trader do bid-ask spread scalping through algo-trading?
"In US public stock markets there is no difference between the actions individual retail traders are ""permitted"" to take and the actions institutional/corporate traders are ""permitted"" to take.  The only difference is the cost of those actions.  For example, if you become a Registered Market Maker on, say, the BATS stock exchange, you'll get some amazing rebates and reduced transaction prices; however, in order to qualify for Registered Market Maker status you have to maintain constant orders in the book for hundreds of equities at significant volumes.  An individual retail trader is certainly permitted to do that, but it's probably too expensive. Algorithmic trading is not the same as automated trading (algorithmic trading can be non-automated, and automated trading can be non-algorithmic), and both can be anywhere from low- to high-frequency.  A low-frequency automated strategy is essentially indistinguishable from a person clicking their mouse several times per day, so: no, from a legal or regulatory perspective there is no special procedure an individual retail trader has to follow before s/he can automate a trading strategy.  (Your broker, on the other hand, may have all sorts of hoops for you to jump through in order to use their automation platform.) Last (but certainly not least) you will almost certainly lose money hand over fist attempting bid-ask scalping as an individual retail trader, whether your approach is algorithmic or not, automated or not.  Why?  Because the only way to succeed at bid-ask scalping is to (a) always be at/near the front of the queue when a price change occurs in your favor, and (b) always cancel your resting orders before they are executed when a price change occurs against you.  Unless your algorithms are smarter than every other algorithm in the industry, an individual retail trader operating through a broker's trading platform cannot react quickly enough to succeed at either of those.  You would have to eschew the broker and buy direct market access to even have a chance, and that's the point at which you're no longer a retail trader. Good luck!"
Many of the Bitcoin exchanges mimic stock exchanges, though they're much more rudimentary offering only simple buy/sell/cancel orders.  It's fairly normal for retail stock brokerage accounts to allow other sorts of more complex orders, where once a certain criteria is met, (the price falls below some $ threshold, or has a movement greater than some %) then your order is executed.  The space between the current buy order and the current sell order is the bid/ask spread, it's not really about timing.  Person X will buy at $100, person Y will sell at $102.  If both had a price set at $101, they would just transact.  Both parties think they can do a little bit better than the current offer.  The width of the bid/ask spread is not universal by any means.  The current highest buy order and the current lowest sell order, are both the current price.  The current quoted market price is generally the price of the last transaction, whether it's buy or sell. 1. Rebate  2. Bid-Ask spread  3. Tactically increasing/decreasing inventory based on their view of the market  4. Picking off idiot traders (OTC markets, basically not passing orders on to the market when the counterparty has a low performance history). "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." The strategy has intrinsic value, which may or may not be obstructed in practice by details mentioned in other answers (tax and other overheads, regulation, risk). John Bensin says that as a general principle, if a simple technical analysis is good then someone will have implemented it before you. That's fair, but we can do better than an existence proof for this particular case, we can point to who is doing approximately this. Market makers are already doing this with different numbers. They quote a buy price and a sell price on the same stock, so they are already buying low and selling high with a small margin. If your strategy works in practice, that means you can make low-risk money from short-term volatility that they're missing out on, by setting your margin at approximately the daily price variation instead of the current bid-offer spread. But market makers choose their own bid-offer spread, and they choose it because they think it's the best margin to make low-risk money in the long run. So you'd be relying that: &gt;If we are looking to offset risk in location A where we are not able to buy forward with location W, and they are the same commodity is this even a common practice in risk management?  Let me prephase this by saying I don't do work directly in this area, but sometimes I analyze what's happening in less liquid markets compared to more liquid markets in various commodities to get a better sense of the supply and demand dynamics of the market.   It's normal - but just looking at the ratios - it looks like the spread is quite volatile - it looks like the price at location W went from trading at 130% of location A to 170% of the price at location A. (I also don't use R so I don't know which time period was the start and which was the end)  What moved in one direction can definitely reverse. If you don't know what is driving this movement in the spread then adding the hedge could be riskier than not having any hedge on. And there are scenarios where the price of the commodity you want to buy at location A is going to rise towards the price at liquid location W and if you are unable to buy it and store it then there isn't much you can do to hedge your company's exposure. "I am strongly skeptical of this.  In fact, after reading your question, I did the following: I wrote a little program in python that ""simulates"" a stock by flipping a coin. Each time the coin comes up heads, the stock's value grows by 1. Each time the coin comes up tails, the stock's value drops by 1.  I then group, say, 50 of these steps into a ""day"", and for each day I look at opening, closing, maximum and minimum. This is then graphed in a candlestick chart.  Funny enough, those things look exactly like the charts analysts look at. Here are a few examples:    If you want to be a troll, show these to a technical analyst and ask them which of these stocks you should sell short and which of them you should buy. You can try this at home, I posted the code here and it only needs Python with a few extra packages (Numpy and Pylab, should both be in the SciPy package). In reply to a comment from JoeTaxpayer, let me add some more theory to this. My code actually performs a one-dimensional random walk. Now Joe in the comments says that an infinite number of flips should approach the zero line, but that is not exactly correct. In fact, there is a high chance to end up far from the zero line, because the expected distance from the start for a random walk with N steps is sqrt(N).  What does indeed approach the zero line is if you took a bunch of these random walks and then performed the average over those. There is, however, one important aspect in which this random walk differs from the stock market: The random walk can go down as far as it likes, whereas a stock has a bottom below which it cannot fall. Reaching this bottom means the company is bankrupt and gets removed from the market. This means that the total stock market, which we might interpret as a sum of random walks, does indeed have a bias towards upwards movement, since I'm only averaging over those random walks that don't go below a certain threshold. But you can really only benefit from this effect by being broadly diversified." Why wouldn't you expect a long-term profit?  Say you buy 100 shares of company X, selling for$1/share today.  You hold it for 20 years, after which it's worth $10/share (in inflation-adjusted dollars).  So you've made a profit, only making two trades (buy & sell).  What the algorithmic traders have done with short-term trades during those 20 years is irrelevant to you. Now expand the idea.  You want some diversification, so instead of one stock, you buy a bit of all the stocks on whatever index interests you, and you just hold them for the same 20 years.  How has what the short-term traders done in the intervening time affected you? Which is what [flash trading](http://www.investopedia.com/financial-edge/0809/flash-trading-wall-streets-latest-scam.aspx) is for.   edit: I promise you, you could. You would just need a faster line. I promise that's why the NYSE banned it. However, that still doesn't mitigate the problem of creating your own exchange. You are looking for arbitrage, not in real terms, and you may lose heavily. Big banks would suck out all profit before you get a chance to react. There are thousands of algorithmic trading systems in banks, which specifically predict such situations and try to make money from such moves. If you can invest in such a system, probably you can make a killing, else best is to forget about it. Remember that somebody before you has surely thought about it and put a system in place, so that somebody else cannot make money out of it before he/she does. A tax of 0.01 cents on a transaction though would mean you'd wait until the spread was at least 0.02 cents before making the trade. But I particularly think the offender is not even day traders, it's the completely ridiculous fact that a person will offer to buy stock at a certain price, or lower,  another person will offer to sell the stock at a lower price, and before the transaction is completed another broker buys the stock and resells it, because his computer is located closer to the data center than either of the other two persons.  That guy is making money and wasting electricity and real estate to get it, and the ultimate purchaser is getting a worse deal.  We still have that problem, but the margins have been squeezed on the HTF guy a bit, so maybe it isn't an issue. This guy is literally proposing a bucket shop. Trades against customers and copy their trades. No centralized clearing (it's not executing trades at all). And he thinks these are good things that customers should get him for.  Scam. And a very old one at that. You can't tell for sure.  If there was such a technique then everyone would use it and the price would instantly change to reflect the future price value. However, trade volume does say something.  If you have a lemonade stand and offer a large glass of ice cold lemonade for 1c on a hot summer day I'm pretty sure you'll have high trading volume.  If you offer it for $5000 the trading volume is going to be around zero. Since the supply of lemonade is presumably limited at some point dropping the price further isn't going to increase the number of transactions.   Trade volumes reflect to some degree the difference of valuations between buyers and sellers and the supply and demand.  It's another piece of information that you can try looking at and interpreting.  If you can be more successful at this than the majority of others on the market (not very likely) you may get a small edge.  I'm willing to bet that high frequency trading algorithms factor volume into their trading decisions among multiple other factors. The strategy could conceivably work if you had sufficient quantity of shares to fill all of the outstanding buy orders and fill your lower buy orders.  But in this case you are forcing the market down by selling and reinforcing the notion that there is a sell off by filling ever lower buy orders.  There is the potential to trigger some stop loss orders if you can pressure it low enough.  There is a lot of risk here that someone sees what you are doing and decides to jump in and buy forcing the price back up.  Could this work sure.  But it is very risky and if you fail to create the panic selling then you risk losing big.  I also suspect that this would violate SEC Rules and several laws.  And if the price drops too far then trading on the stock would be halted and is likely to return at the appropriate price. Bottom line I can not see a scenario where you do not trigger the stop, net a profit and end up with as many or more stock that you had in the first place. You want to sell for 61.15, but the most the best buyer will pay is 61.10? The HFT trader forces you both to trade over a gap of a nickel AND makes a nickel in profit??      How does he do that, with magic? "This is the best tl;dr I could make, [original](https://www.nytimes.com/2017/07/17/business/dealbook/student-loan-debt-collection.html) reduced by 85%. 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