Why do requirements after a margin call vary?
Initial Margins and Maintenance margins can be used for both stocks as well as futures. It depends on which broker you use and what services they offer. The initial Margin is used to cover the purchase, the maintenance margin is used to ask additional funds in case the value of the underlying equity changes drastically before settlement. You can start with the investopedia article on initial margin and Maintenance margin I believe the reasons:
"As previously answered, the solution is margin. It works like this: You deposit e.g. 1'000 USD at your trading company. They give you a margin of e.g. 1:100, so you are allowed to trade with 100'000 USD.  Let's say you buy 5'000 pieces of a stock at $20 USD (fully using your 100'000 limit), and the price changes to $20.50 . Your profit is 5000* $0.50 = $2'500. Fast money? If you are lucky. Let's say before the price went up to 20.50, it had a slight dip down to $19.80. Your loss was 5000* $0.2 = 1'000$. Wait! You had just 1000 to begin with: You'll find an email saying ""margin call"" or ""termination notice"": Your shares have been sold at $19.80 and you are out of business. The broker willingly gives you this credit, since he can be sure he won't loose a cent. Of course you pay interest for the money you are trading with, but it's only for minutes. So to answer your question: You don't care when you have ""your money"" back, the trading company will always be there to give you more as long as you have deposit left. (I thought no one should get margin explained without the warning why it is a horrible idea to full use the ridiculous high margins some broker offer. 1:10 might or might not be fine, but 1:100 is harakiri.)" However, is it a risk that they may withhold liquidity in a market panic crash to protect their own capital?  Two cases exist here. One is if you access the direct market, then they cannot. Secondly if you are trading in the internal market created by them, yes they can do to save their behind, but that is open to question. They don't make money on your profit or loss, their money comes from you trading. So as long as you maintain the required margin in your accounts, you can go ahead. I had a mail exchange with IG Index regarding this and they categorically refuted on this point. Will their clients be unable to sell at a fair market price in a panic crash? No. Also, do CFD providers sometimes make an occasional downward spike to cream off their clients' cut-loss order?  Need proof regarding this, not saying it cannot happen. They wouldn't antagonize the people bringing them business without any reason. They would be putting their money at risk. But you should know, their traders are also in the market. Which might look skimming your money, it would be their traders making money in the free market. After all Google, Facebook etc also sell your personal data for profit, why shouldn't the CFD firm also. Since they are market makers, what is to prevent them from attempting these tricks? Are these concerns also valid for forex brokers serving the retail public? What you consider as tricks are legitimate use of information to make money. What I did not understand when I first called is that margin able account means the ability to borrow margin, but not the necessity of borrowing. Like I was saying, it is something I am going to do a lot of due diligence on before I plunge in. I have a general vague idea of futures, and thus why I was asking for info on the matter. Most brokers have a margin maintenance requirement of 30%.  In your example, it would depend on how much money you're borrowing from your broker on margin. Consider this: You have $250, and short AAPL at $500 on margin. This would be a common scenario (federal law requires investors to have at least 50% of their margin equity when opening a transaction). If your broker had a requirement of 30%, they would require that for your $500 position, you have at least $500 * .3 = $150 equity. Since you are currently above that number at $250, you will not be hit with a margin call. Say the price of AAPL doubles, and now your position is worth $1000. $1000 * .3 = $300, which is $50 above your initial equity. Your broker will now consider you eligible for a margin call. Most will not execute the call right away, you will often have some time to either sell/cover stock or add funds to your account. But not all brokers will warn you if you are breaking margin requirements, and sometimes margin calls can take you by surprise if you are not paying attention. Also, many will charge interest on extra margin borrowed. "According to page 56 of the 2015 IRS Publication 550 on Investment Income and Expenses: Wash sales. Your holding period for substantially identical stock or securities you acquire in a wash sale includes the period you held the old stock or securities. It looks like the rule applies to stocks and other securities, including options. It seems like the key is ""substantially identical"". For your brokerage / trading platform to handle these periods correctly for reporting to IRS, it seems best to trade the same security instead of trying to use something substantially identical." I understand the question, I think. The tough thing is that trades over the next brief time are random, or appear so. So, just as when a stock is $10.00 bid / $10.05 ask, if you place an order below the ask, a tick down in price may get you a fill, or if the next trades are flat to higher, you might see the close at $10.50, and no fill as it never went down to your limit.  This process is no different for options than for stocks.  When I want to trade options, I make sure the strike has decent volume, and enter a market order. Edit - I reworded a bit to clarify. The Black–Scholes is a model, not a rigid equation. Say I discover an option that's underpriced, but it trades under right until it expires. It's not like there's a reversion to the mean that will occur. There are some very sophisticated traders who use these tools to trade in some very high volumes, for them, it may produce results. For the small trader you need to know why you want to buy a stock or its option and not worry about the last $0.25 of its price. You have to call Interactive Brokers for this. This is what you should do, they might even have a web chat. These are very broker specific idiosyncrasies, because although margin rules are standardized to an extent, when they start charging you for interest and giving you margin until settlement may not be standardized. I mean, I can call them and tell you what they said for the 100 rep. The 2 and 20 rule is a premium arrangement that hedge funds offer and venture capital funds offer, and they also offer different variations of it. The 2 is the management fee as percent of assets under management, the 20 is the profit cut, which they only get if they are profitable. There are 0/20, 1/15, and many variations. You're assuming that nobody offers this arrangement because it isn't offered to you, but that's because nobody offers it to people that aren't wealthy enough to legally qualify for their fund. When you park 6 or 7 figure amounts in bank accounts, they'll send your information out to the funds that operate the way you wish they operated.