Why do mutual fund trading limitations exist? e.g. 90 day transfer limits?
Mutual funds (that are not exchange-traded funds) often need to sell some  of their securities to get cash when a shareholder redeems some shares. Such transactions incur costs that are paid (proportionally) by all the shareholders in the fund, not just the person requesting redemption, and thus the remaining shareholders get a lower return. (Exchange-traded funds are traded as if they are shares of common stock,  and a shareholder seeking a redemption pays the costs of the redemption). For this reason, many mutual funds do not allow redemptions for some period of time after a purchase, or purchases for some period of time after a redemption. The periods of time are chosen by the fund, and are stated in the prospectus (which everyone has acknowledged has been received before an investment was made).
"The issues of trading with unsettled funds are usually restricted to cash accounts.  With margin, I've never personally heard of a rule that will catch you in this scenario.  You won't be able to withdraw funds that are tied up in unsettled positions until the positions settle.  You should be able to trade those funds.  I've never heard of a broker charging margin interest on unsettled funds, but that doesn't mean there isn't a broker somewhere that does. Brokers are allowed to impose their own restrictions, however, since margin is basically offering you a line of credit.  You should check to see if your broker has more restrictive rules. I'd guess that you may have heard about restrictions that apply to cash accounts and think they may also apply to margin accounts.  If that's the case and you want to learn more about the rules generally, try searching for these terms: You should be able to find a lot of clear resources on those terms.  Here's one that's current and provides examples: https://www.fidelity.com/learning-center/trading-investing/trading/avoiding-cash-trading-violations On a margin account you avoid these issue because the margin (essentially a loan from your broker) provides a cushion / additional funds that avoid the issues.  It is possible that if you over-extend yourself that you'll get a ""margin call,"" but that seems to be different than what you're asking and maybe worth a new question if you want to know about that." "Often these types of trades fall into two different categories.   An error by broker or exchange.  Exchange clearing out part of their books incorrectly is an example.  Most exchanges make firms reopen their positions for after market hours.  There may have been an issue doing so or exchange could incorrectly cancel positions.  I was in the direct feed industry for years and this was a big issue.  At the same time the broker can issue a no limit buy on accident (or has software that is prospecting and said software has a bug or written poorly).   unscrupulous parties looking to feign an upswing or downswing in market.  Let's say you hold 500k shares in a stock that sells for $11.  You could possibly buy 100 shares for $13.  Trust me you will find a seller.  Then you are hoping that people see that trade as a ""norm"" and trade from there, allowing you to rake in $1M for spending an extra $200 - NOTE this is not normal and an extreme example.  This was so common in the early days of NASDAQ after hours that they discontinued using the after hours trades as part of historical information that they keep like daily/yearly high or closing price.  The liquidity allows for manipulation.  It isn't seen as much now since this has been done a million times but it does still happen." Brokerage firms must settle funds promptly, but there's no explicit definition for this in U.S. federal law. See for example, this article on settling trades in three days. Wikipedia also has a good write-up on T+3. It is common practice, however. It takes approximately three days for the funds to be available to me, in my Canadian brokerage account. That said, the software itself prevents me from using funds which are not available, and I'm rather surprised yours does not. You want to be careful not to be labelled a pattern day trader, if that is not your intention. Others can better fill you in on the consequences of this. I believe it will not apply to you unless you are using a margin account. All but certainly, the terms of service that you agreed to with this brokerage will specify the conditions under which they can lock you out of your account, and when they can charge interest. If they are selling your stock at times you have not authorised (via explicit instruction or via a stop-loss order), you should file a complaint with the S.E.C. and with sufficient documentation. You will need to ensure your cancel-stop-loss order actually went through, though, and the stock was sold anyway. It could simply be that it takes a full business day to cancel such an order. High frequency trades are intra day. The would buy a stock for 100 and sell for 100.10 multiple times. So If you start with 100 in your broker account, you buy something [it takes 2-3 days to settle], you sell for 100.10 [it takes 2-3 days to settle]. You again buy something for 100. It is the net value of both buys and sells that you need to look at. Trading on Margin Accounts. Most brokers offer Margin Accounts. The exact leverage ratios varies. What this means is that if you start with 10 [or 15 or 25] in your broker you can buy stock of 100. Of course legally you wont own the stock unless you pay the broker balance, etc. According to Regulation T, you can make as many day trade (round trip) stock purchases using a cash account as long as you have the funds to cover each and every round trip sale. However, the funds generated from the sales cannot be used again to purchase new stocks until the settlement period (T-2 or T-3) is over. For example, say you have $10000 dollars in your cash account and no securities. You buy 1000 shares of XYZ stock in the morning at one dollar per share and you sell the stock 30 minutes later because it went up say by 50 cents. According to Regulation T, you cannot use the money generated from the sale of your 1000 shares until after the settlement date. However, you can use the remaining $9000 dollars in your account to execute other trades just as the first trade. You can do this as many times as you want as long as you have funds available to pay for the transaction the same day it's executed. The only thing to worry about and that isn't clear, is, what happens if you perform this action more than 3 times in a week? Does it mean that your cash account now becomes a margin account subject to margin account rules because you executed more than three round trip trades in a five day rolling period? You set it based on liquidity management. Cash drag is one of the reasons actively managed funds underperform. The longer your settlement date, the less cash you have to hold because you can take three days to liquidate positions to redeem. So it's a convenience vs performance question. This is more than likely a thing about your financial institution and the exchanges where they trade shares. Some exchanges cannot/will not handle odd lot transactions. Most established brokerages have software and accounting systems that will deal in round lots with the exchanges, but can track your shares individually. Sometimes specific stocks cannot be purchased in odd lots due to circumstances specific to that stock (trading only on a specific exchange, for example).  Most brokerages offer dollar-cost averaging programs, but may limit which stocks are eligible, due to odd lot and partial share purchases. Check with your brokerage to see if they can support odd lot and/or DCA purchases. You may find another similar ETF with similar holdings that has better trading conditions, or might consider an open-end mutual fund with similar objectives. Mutual funds allow partial share purchases (you have $100 to invest today, and they issue you 35.2 shares, for example). "They're taking advantage of float.  Like so many things in the financial world today, this practice is a (strictly legal) fraud. When you make the transaction, the money is available immediately, for reasons that should be intuitively obvious to anyone who's ever used PayPal.  It doesn't take 3 minutes for the broker to get that money, let alone 3 days.  But if they can hold on to that money instead of turning it over to you, they can make money from it for themselves, putting money that rightfully belongs to you to work for them instead, earning interest on short-term loans, money market accounts, etc. The SEC mandates that this money must be turned over to you within 3 days so it should not surprise anyone that that's exactly how long the ""we have to wait for it to clear"" scam runs for.  Even if it doesn't seem like very much money per transaction, for a large brokerage with hundreds of thousands of clients, all the little bits add up very quickly.  This is why they feel no need to compete by offering better service: offering poor service is making them a lot of money that they would lose by offering better service." Another explanation is that they keep your money three days to make money with it, because they can. The other reasons might have been valid 100 years ago, and no bank would voluntarily cut that down until forced by law. Example: In Europe, bank to bank transfers used to take three days, until a law forced them to give next day, and suddenly it was possible. One of the often cited advantages of ETFs is that they have a higher   liquidity and that they can be traded at any time during the trading   hours. On the other hand they are often proposed as a simple way to   invest private funds for people that do not want to always keep an eye   on the market, hence the intraday trading is mostly irrelevant for   them. I am pretty sure that this is a subjective idea. The fact is you may buy GOOG, AAPL, F or whatever you wish(ETF as well, such as QQQ, SPY etc.) and keep them for a long time. In both cases, if you do not want to keep an on the market it is ok. Because, if you keep them it is called investment(the idea is collecting dividends etc.), if you are day trading then is it called speculation, because you main goal is to earn by buying and selling, of course you may loose as well. So, you do not care about dividends or owning some percent of the company. As, ETFs are derived instruments, their volatility depends on the volatility of the related shares. I'm wondering whether there are secondary effects that make the   liquidity argument interesting for private investors, despite not   using it themselves. What would these effects be and how do they   impact when compared, for example, to mutual funds? Liquidity(ability to turn cash) could create high volatility which means high risk and high reward. From this point of view mutual funds are more safe. Because, money managers know how to diversify the total portfolio and manage income under any market conditions. "If anything, the price of an ETF is more tightly coupled to the underlying holdings or assets than a mutual fund, because of the independent creation/destruction mechanism. With a mutual fund, the price is generally set once at the end of each day, and the mutual fund manager has to deal with investments and redemptions at that price. By the time they get to buying or selling the underlying assets, the market may have moved or they may even move the market with those transactions. With an ETF, investment and redemption is handled by independent ""authorized participants"". They can create new units of the ETF by buying up the underlying assets and delivering them to the ETF manager, and vice versa they can cancel units by requesting the underlying assets from the ETF manager. ETFs trade intraday (i.e. at any time during trading hours) and any time the price diverges too far from the underlying assets, one of the authorized participants has an incentive to make a small profit by creating or destroying units of the ETF, also intraday." This is to protect your position in specific highly volatile market conditions.  If the stock is free falling and you only have a stop order at $90, it's possible that this order could be filled at $50 or even less. The limit is to protect you from that, as there are certain very specific times where it's better to just hold the stock instead of taking a huge loss (ie when price is whipsawing). Mutual funds don't have intraday prices. They have net asset values which are calculated periodically (daily or weekly or any other period depending on the fund). "Give me your money. I will invest it as I see fit. A year later I will return the capital to you, plus half of any profits or losses. This means that if your capital under my management ends up turning a profit, I will keep half of those profits, but if I lose you money, I will cover half those losses. Think about incentives. If you wanted an investment where your losses were only half as bad, but your gains were only half as good, then you could just invest half your assets in a risk-free investment. So if you want this hypothetical instrument because you want a different risk profile, you don't actually need anything new to get it. And what does the fund manager get out of this arrangement? She doesn't get anything you don't: she just gets half your gains, most of which she needs to set aside to be able to pay half your losses. The discrepancy between the gains and losses she gets to keep, which is exactly equal to your gain or loss. She could just invest her own money to get the same thing. But wait -- the fund manager didn't need to provide any capital. She got to play with your money (for free!) and keep half the profits. Not a bad deal, for her, perhaps... Here's the problem: No one cares about your thousands of dollars. The costs of dealing with you: accounting for your share, talking to you on the phone, legal expenses when you get angry, the paperwork when you need to make a withdrawal for some dental work, mailing statements and so on will exceed the returns that could be earned with your thousands of dollars. And then the SEC would probably get involved with all kinds of regulations so you, with your humble means and limited experience, isn't constantly getting screwed over by the big fund. Complying with the SEC is going to cost the fund manager something. The fund manager would have to charge a small ""administrative fee"" to make it worthwhile.  And that's called a mutual fund. But if you have millions of free capital willing to give out, people take notice. Is there an instrument where a bunch of people give a manager capital for free, and then the investors and the manager share in the gains and losses? Yes, hedge funds! And this is why only the rich and powerful can participate in them: only they have enough capital to make this arrangement beneficial for the fund manager." "First it is worth noting the two sided nature of the contracts (long one currency/short a second) make leverage in currencies over a diverse set of clients generally less of a problem.  In equities, since most margin investors are long ""equities"" making it more likely that large margin calls will all be made at the same time. Also, it's worth noting that high-frequency traders often highly levered make up a large portion of all volume in all liquid markets ~70% in equity markets for instance.  Would you call that grossly artificial?  What is that volume number really telling us anyway in that case? The major players holding long-term positions in the FX markets are large banks (non-investment arm), central banks and corporations and unlike equity markets which can nearly slow to a trickle currency markets need to keep trading just for many of those corporations/banks to do business.  This kind of depth allows these brokers to even consider offering 400-to-1 leverage.  I'm not suggesting that it is a good idea for these brokers, but the liquidity in currency markets is much deeper than their costumers."