question about short selling stocks
If you had an agreement with your friend such that you could bring back a substantially similar car, you could sell the car and return a different one to him.  The nature of shares of stock is that, within the specified class, they are the same.  It's a fungible commodity like one pound of sand or a dollar bill.  The owner doesn't care which share is returned as long as a share is returned.   I'm sure there's a paragraph in your brokerage account terms of service eluding to the possibility of your shares being included in short sale transactions. The original owner of the shares can pledge their shares to be short, and they earn interest from lending their shares. The conditions of this arrangement are detailed in standard agreements all market participants sign with their broker, or clearinghouse, or with the exchange, or with the self regulatory agency. Stocks within the same class are identical, despite someone's sentiment to an old share certificate that their grandparents gave them, and as such can be sold and returned to the beneficial owner multiple times with no difference. That is how it is supposed to work anyway, as naked shorting involves selling fictional shares that have no beneficial owner. So there are market inefficiencies in this practice, but the agreements between market participants are sound and answers your question about how. "My take on this is that with any short-selling contract you are engaging in, at a specified time in the future you will need to transfer ownership of the item(s) you sold to the buyer. Whether you own the item(s) or in your case you will buy your friend's used  car in the meantime (or dig enough gold out of the ground - in the case of hedging a commodity exposure) is a matter of ""trust"". Hence there is normally some form of margin or credit-line involved to cover for you failing to deliver on expiry."
Your question is missing too much to be answered directly. Instead - here are some points to consider. Short term gains taxed at your marginal rates, whereas long term gains have preferable capital gains rates (up to 20% tax rate, instead of your marginal rate). So if you're selling at gain, you might want to consider to sell FIFO and pay lower capital gains tax rate instead of the short term marginal rate. If you're selling at loss and have other short term gains, you would probably be better selling LIFO, so that the loss could offset other short term gains that you might have.  If you're selling at loss and don't have short term gains to offset, you can still offset your long term gains with short term losses, but the tax benefit will be lower. In this case - FIFO might be a better choice again. If you're selling at loss, beware of the wash sale rules, as you might not be able to deduct the loss if you buy/sell within too short a window. "The correct answer to this question is:  the person who the short sells the stock to. Here's why this is the case.  Say we have A, who owns the stock and lends it to B, who then sells it short to C. After this the price drops and B buys the stock back from D and returns it to A. The outcome for A is neutral.  Typically stock that is sold short must be held in a margin account; the broker can borrow the shares from A, collect interest from B, and A has no idea this is going on, because the shares are held in a street name (the brokerage's name) and not A. If A decides during this period to sell, the transaction will occur immediately, and the brokerage must shuffle things around so the shares can be delivered.  If this is going to be difficult then the cost for borrowing shares becomes very high. The outcome for B is obviously a profit: they sold high first and bought (back) low afterwards. This leaves either C or D as having lost this money.  Why isn't it D? One way of looking at this is that the profit to B comes from the difference in the price from selling to C and buying from D.  D is sitting on the low end, and thus is not paying out the profit.  D bought low, compared to C and this did not lose any money, so C is the only remaining choice. Another way of looking at it is that C actually ""lost"" all the money when purchasing the stock.  After all, all the money went directly from C to B.  In return, C got some stock with the hope that in the future C could sell it for more than was paid for it.  But C literally gave the money to B, so how could anybody else ""pay"" the loss? Another way of looking at it is that C buys a stock which then decreases in value.  C is thus now sitting on a loss.  The fact that it is currently only a paper loss makes this less obvious; if the stock were to recover to the price C bought at, one might conclude that C did not lose the money to B.  However, in this same scenario, D also makes money that C could have made had C bought at D's price, proving that C really did lose the money to B. The final way of seeing that the answer is C is to consider what happens when somebody sells a stock which they already hold but the price goes up; who did they lose out on the gain to?  The person again is; who bought their stock.  The person would buys the stock is always the person who the gain goes to when the price appreciates, or the loss comes out of if the price falls." why can't I just use the same trick with my own shares to make money on the way    down? Because if you sell shares out of your own portfolio, by definition, you are not selling short at all. If you sell something you own (and deliver it) - then there is no short involved. A short is defined as a net negative position - i.e. you sell shares you do not have. Selling shares you own is selling shares you own - no short involved. You must borrow the shares for a short because in the stock market, you must DELIVER. You can not deliver shares you do not own. The stock market does not work on promises - the person who bought the shares expects ownership of them with all rights that gives them. So you borrow them to deliver them, then return them when you buy them back. That's because they literally could not help you. It's not that they were just unwilling to. A hedge fund manager might be able to do it, because the person who bet on Facebook would be willing to let him borrow their shares.  An IPO in explain like I'm five:  A bank helps underwrite the shares pre offering. This means they buy the shares wholesale. They buy a large majority of the company in order to offer them to the public when the stock goes public. The bank does this for profit, the company does this become it helps raise their price. The bank that underwrites the stock is legally prohibited from short selling that stock for ***at least***  30 days before the IPO. This is to prevent the bank from trying to commit fraud by selling stock out the front door and betting against it out the back.   ***  So, now let's jump forward to the day of the IPO. The bank is offering stock to everyone who wants to buy it (other banks who will cut it up and sell it to more people). In order to short the stock someone must be willing to let you borrow their shares. Only the bank that underwrote it prohibited from short selling. It's possible but hard. The underwriter has the majority of the shares for the first thirty days anyways. They're just going to release enough of them to raise volume on the ticker symbol (volume is the amount of people buying and selling). The others the underwriter sold to are unwilling to let someone borrow their stock because they want to ride the price hike and shares are in short supply. So while it's possible to short shares, it's very hard. The underwriters limit the supply of shares to prevent that from happening. The underwriters can't just let you short their own shares because they are legally prohibited from it.   Basically, you're left with the fact that the only person who has enough supply to let you short, is prohibited by law from letting you do it. I'm sure Morgan Stanley would have been happy to let their customers short Facebook (as long as you did it through them) to hedge their bets. But they can't. Shorting is the term used when someone borrows a stock and sells it at the current price to then buy it back later at hopefully a lower price. There are rules about this as noted in the link that begins this answer as there are risks to selling a stock you don't own of course. If you look up various large companies you may find that there are millions of shares sold short throughout the market as someone does have the shares and they will need to be put back eventually. The whole point of buying puts is cheaper cost and lower downside risk. If you short the box, you are assuming he already holds gold holdings to short against. It's not the same as short selling where you borrow shares.  Either way, you are far more vulnerable to downside risk if you are short the stock (whether you borrowed or shorted already owned shares). If Gold suddenly has a 20% pop over the next year, which could be possible given the volatility and uncertainty in the marketplace, you have big trouble. Whereas, if you buy puts, you only lose your costs for the contracts. The amount that you miss by in your bet isn't going to factor into anything. In order: A seller of the stock (duh!). You don't know who or why this stock was sold. It could be any reason, and is of no concern of yours. It doesn't matter. Investors (pension funds, hedge funds, individual investors, employees, management) sell stock for many reasons: need cash, litigation, differing objectives, sector rotation, etc. To you, this does not matter. Yes, it does affect stock market prices: If you were not willing to buy that amount of shares, and there were no other buyers at that price, the seller would likely choose to lower the price offered. By your purchase, you are supporting the price. The point of short-selling as a separate instrument is that you can you do it when you can't sell the underlying asset... usually because you don't actually own any of it and in fact believe that it will go down. Shorting allows you to profit from a falling price. Another (non-speculative) possibility is that you don't have the underlying asset right now (and thus can't sell it) but will get it at a certain point in the future, e.g. because it's bonds that you've used to guarantee a loan... or grain that's still growing on your fields.