Can I use my long position stocks as margin for my short sold stocks?
200% margin for a short sale is outrageous. You should only need to put up 150% margin, of which 50% is your money, and the 100% is the proceeds.  With $100 of your money, you should be able to buy $100 of GOOG and short $100 of PNQI.
"When portfolio positions are reported in percentages, those percentages are relative to the portfolio's base equity.  When you start out, that is equal to the cash you have in a portfolio.  Later it's the net equity of the portfolio (i.e., how much money you could withdraw if you were to exit all your positions). If you put $5,000 into your account and are long and short 50%, then you are long $2,500 and short $2,500.  If it's 100% and -100%, then long and short $5,000. ""Leverage"" is often computed gross (as if all positions were long).  So if you have 100% and -100%, then your broker may say you are ""levered 2 to 1.""  That is, your gross exposure is twice as large as your underlying base equity." "You should check with your broker for details, but you can generally specify which ""lot"" you are selling.  where I've seen it, that's done by concurrently sending a ""letter of instruction"" documenting your choice of lot concurrent with the sale, but different brokers may handle this differently.  I would think this should work for the case that you describe. (In addition, the default rule used by your broker is ""probably"" first-in-first-out, which will do what you want here.) Note that this may come into play even in a margin account to the extent that you might want to specify a lot in order to obtain (or set yourself up for later benefit of) favorable tax treatment under the long-term capital gains rules" There is no difference.  When dealing with short positions, talking about percentages become very tricky since they no longer add up to 100%.  What does the 50% in your example mean?  Unless there's some base amount (like total amount of the portfolio, then the percentages are meaningless.  What matters when dealing with long and short positions is the net total - meaning if you are long 100 shares on one stock trade and short 50 shares on another, then you are net long 50 shares. Yes, you call the broker and tell him to use those shares to deliver to the short position. Yes, theoretically you can flip the shares you agreed to buy and make a profit, but you're banking on the market behaving in some very precise and potentially unlikely ways.  In practice it's very tricky for you to successfully navigate paying arbitrarily more for a stock than it's currently listed for, and selling it back again for enough to cover the difference.  Yes, the price could drop to $28, but it could just as easily drop to $27.73 (or further) and now you're hurting, before even taking into account the potentially hefty commissions involved. Another way to think about it is to recognize that an option transaction is a bet; the buyer is betting a small amount of money that a stock will move in the direction they expect, the seller is betting a large amount of money that the same stock will not.  One of you has to lose.  And unless you've some reason to be solidly confident in your predictive powers the loser, long term, is quite likely to be you. Now that said, it is possible (particularly when selling puts) to create win-win scenarios for yourself, where you're betting one direction, but you'd be perfectly happy with the alternative(s).   Here's an example.  Suppose, unrelated to the option chain, you've come to the conclusion that you'd be happy paying $28 for BBY.  It's currently (June 2011) at ~$31, so you can't buy it on the open market for a price you'd be happy with.  But you could sell a $28 put, promising to buy it at that price should someone want to sell it (presumably, because the price is now below $28). Either the put expires worthless and you pocket a few bucks and you're basically no worse off because the stock is still overpriced by your estimates, or the option is executed, and you receive 100 shares of BBY at a price you previously decided you were willing to pay.  Even if the list price is now lower, long term you expect the stock to be worth more than $28.  Conceptually, this makes selling a put very similar to being paid to place a limit order to buy the stock itself. Of course, you could be wrong in your estimate (too low, and you now have a position that might not become profitable; too high, and you never get in and instead just watch the stock gain in value), but that is not unique to options - if you're bad at estimating value (which is not to be confused with predicting price movement) you're doomed just about whatever you do. "If you sell a stock you don't own, it's called a short sale. You borrowed the shares from an owner of the stock and eventually would buy to close. On most normal shares, you can hold a short position indefinitely, but there are some shares that have a combination of either a small float or too high a short position that shares to short are not available.  This can create a ""short squeeze"" where shorts are burned by being forced to buy the stock back.  Last - when you did this, you should have instructed the broker that you were ""selling to open"" or ""selling short."" In the old days, when people held stock certificates, you were required to send the certificate in when you sold. Today, the broker should know that wasn't your intention." If the position starts losing money as soon as it is put on, then I would close it out ,taking a small loss. However, if it starts making money,as in the stock inches higher, then you can use part of the premium collected to buy an out of money put, thereby limiting your downside. It is called a collar. 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. A long put - you have a small initial cost (the option premium) but profit as the stock goes down. You have no additional risk if the shock rises, even a lot. Short a stock - you gain if the stock drops, but have unlimited risk if it rises, the call mitigates this, by capping that rising stock risk. The profit/loss graph looks similar to the long put when you hold both the short position and the long call.  You might consider producing a graph or spreadsheet to compare positions. You can easily sketch put, call, long stock, short stock, and study how combinations of positions can synthetically look like other positions. Often, when a stock has no shares to short, the synthetic short can help you put your stock position in place. When you sell a stock that you own, you realize gains, or losses. Short-term gains, realized within a year of buying and selling an asset, are taxed at your maximum (or marginal) tax rate. Long term-gains, realized after a year, are taxed at a lower, preferential rate. The first thing to consider is losses. Losses can be cancelled against gains, reducing your tax liability. Losses can also be carried over to the next tax year and be redeemed against those gains. When you own a bunch of the same type of stock, bought at different times and prices, you can choose which shares to sell. This allows you to decide whether you realize short- or long-term gains (or losses). This is known as lot matching (or order matching). You want to sell the shares that lost value before selling the ones that gained value. Booking losses reduces your taxes; booking gains increases them. If faced with a choice between booking short term and long term losses, I'd go with the former. Since net short-term gains are taxed at a higher rate, I'd want to minimize the short-term tax liability before moving on to long-term tax liability. If my remaining shares had gains, I'd sell the ones purchased earliest since long-term gains are taxed at a lower rate, and delaying the booking of gains converts short-term gains into long-term ones. If there's a formula for this, I'd say it's  (profit - loss) x (tax bracket) = tax paid "I would think that a lot of brokers would put the restriction suggested in @homer150mw in place or something more restrictive, so that's the first line of answer. If you did get assigned on your short option, then (I think) the T+3 settlement rules would matter for you.  Basically you have 3 days to deliver.  You'll get a note from your broker demanding that you provide the stock and probably threatening to liquidate assets in your account to cover their costs if you don't comply.  If you still have the long-leg of the calendar spread then you can obtain the stock by exercising your long call, or, if you have sufficient funds available, you can just buy the stock and keep your long call.  (If you're planning to exercise the long call to cover the position, then you need to check with your broker to see how quickly the stock so-obtained will get credited to your account since it also has some settlement timeline.  It's possible that you may not be able to get the stock quickly enough, especially if you act on day 3.) Note that this is why you must buy the call with the far date.  It is your ""insurance"" against a big move against you and getting assigned on your short call at a price that you cannot cover. With the IRA, you have some additional concerns over regular cash account - Namely you cannot freely contribute new cash any time that you want.  That means that you have to have some coherent strategy in place here that ensures you can cover your obligations no matter what scenario unfolds.  Usually brokers put additional restrictions on trades within IRAs just for this reason. Finally, in the cash account and assuming that you are assigned on your short call, you could potentially could get hit with a good faith, cash liquidation, or free riding violation when your short call is assigned, depending on how you deliver the stock and other things that you're doing in the same account.  There are other questions on that on this site and lots of information online.  The rules aren't super-simple, so I won't try to reproduce them here.  Some related questions to those rules: An external reference also on potential violations in a cash account: https://www.fidelity.com/learning-center/trading-investing/trading/avoiding-cash-trading-violations" If you buy puts, there are no guaranteed proceeds though.  If you short against the box, you've got immediate proceeds with a nice capital loss if it doesn't work out.  Conversely, you could write a covered call, take the contract proceeds, and write off the long position losses.  Nobody ever factors tax consequences into the equation here. No, CFD is not viable as a long term trading strategy.  You have a minimum margin to maintain, and you are given X days to top up your margin should you not meet the margin requirements. Failure to meet margin requirements will result in a forced sell where you are no longer able to hold onto the stock. A long term trading strategy is where you hold onto the stock through the bad times of the company and keep it long enough to see the good times. However, with CFD, you may be forced to sell before you see the good times. In addition, you incur additional lending charges (e.g. 4%-6%) for the ability to leverage. "Simplest way to answer this is that on margin, one is using borrowed assets and thus there are strings that come with doing that. Thus, if the amount of equity left gets too low, the broker has a legal obligation to close the position which can be selling purchased shares or buying back borrowed shares depending on if this is a long or short position respectively. Investopedia has an example that they walk through as the call is where you are asked to either put in more money to the account or the position may be closed because the broker wants their money back. What is Maintenance Margin? A maintenance margin is the required   amount of securities an investor must hold in his account if he either   purchases shares on margin, or if he sells shares short. If an   investor's margin balance falls below the set maintenance margin, the   investor would then need to contribute additional funds to the account   or liquidate stocks in the account to bring the account back to the   initial margin requirement. This request is known as a margin call. As discussed previously, the Federal Reserve Board sets the initial   margin requirement (currently at 50%). The Federal Reserve Board also   sets the maintenance margin. The maintenance margin, the amount of   equity an investor needs to hold in his account if he buys stock on   margin or sells shares short, is 25%. Keep in mind, however, that this   25% level is the minimum level set, brokerage firms can increase, but   not decrease this level as they desire. Example: Determining when a margin call would occur. Assume that an   investor had purchased 500 shares of Newco's stock. The shares were   trading at $50 when the transaction was executed. The initial margin   requirement on the account was 70% and the maintenance margin is 30%.   Assume no transaction costs. Determine the price at which the investor   will receive a margin call. Answer: Calculate the price as follows: $50 (1- 0.70) = $21.43 1 - 0.30 A margin call would be received when the price of Newco's stock fell   below $21.43 per share. At that time, the investor would either need   to deposit additional funds or liquidate shares to satisfy the initial   margin requirement. Most people don't want ""Margin Calls"" but stocks may move in unexpected ways and this is where there are mechanisms to limit losses, especially for the brokerage firm that wants to make as much money as possible. Cancel what trade? No, the broker will close the position if the requirement isn't kept. Basically think of this as a way for the broker to get their money back if necessary while following federal rules. This would be selling in a long position or buying in a short sale situation. The Margin Investor walks through an example where an e-mail would be sent and if the requirement isn't met then the position gets exited as per the law." Timothy Sykes specializes in this type of trade, according to his website. He has some recommendations for brokers that allow shorting low-priced stocks: