Odds of early assignment for a short in the money call
It depends how deep in the money it is, compared to the dividend.  Even an in the money call has some time premium. As the call holder, if I exercise instead of selling the call, I am trading the potential for a dividend, which I won't receive, for getting that time premium back by selling.  Given the above, you'll notice a slight distortion in options pricing as a dividend date approaches, as the option will reflect not just the time premium, but the fact that exercising with grab the dividend.  Edit to address your comment - $10 stock, $9 strike, 50 cent div. If the option price is high, say $2, because there's a year till expiration, exercising makes no sense. If it's just $1.10, I gain 40 cents by exercising and selling after the dividend.
"The question you are asking concerns the exercise of a short option position.  The other replies do not appear to address this situation. Suppose that Apple is trading at $96 and you sell a put option with a strike price of $95 for some future delivery date - say August 2016.  The option contract is for 100 shares and you sell the contract for a premium of $3.20. When you sell the option your account will be credited with the premium and debited with the broker commission.  The premium you receive will be $320 = 100 x $3.20.  The commission you pay will depend on you broker. Now suppose that the price of Apple drops to $90 and your option is exercised, either on expiry or prior to expiry.  Then you would be obliged to take delivery of 100 Apple shares at the contracted option strike price of $95 costing you $9,500 plus broker commission.  If you immediately sell the Apple shares you have purchased under your contract obligations, then assuming you sell the shares at the current market price of $90 you would realise a loss of $500 ( = 100x($95-$90) )plus commission.  Since you received a premium of $320 when you sold the put option, your net loss would be $500-$320 = $180 plus any commissions paid to your broker. Now let's look at the case of selling a call option.  Again assume that the price of Apple is $96 and you sell a call option for 100 shares with a strike price of $97 for a premium of $3.60.  The premium you receive would be $360 = 100 x $3.60.  You would also be debited for commission by your broker. Now suppose that the price of Apple shares rises to $101 and your option is exercised.  Then you would be obliged to deliver 100 Apple shares to the party exercising the option at the contracted strike price of $97.  If you did not own the shares to effect delivery, then you would need to purchase those shares in the market at the current market price of $101, and then sell them to the party exercising the option at the strike price of $97.  This would realise an immediate loss of $400 = 100 x ($101-$97) plus any  commission payable.  If you did own the shares, then you would simply deliver them and possibly pay some commission or a delivery fee to your broker.  Since you received $360 when you sold the option, your net loss would be $40 = $400-$360 plus any commission and fees payable to the broker. It is important to understand that in addition to these accounting items, short option positions carry with them a ""margin"" requirement.  You will need to maintain a margin deposit to show ""good faith"" so long as the short option position is open.  If the option you have sold moves against you, then you will be called upon to put up extra margin to cover any potential losses." A bullish (or 'long') call spread is actually two separate option trades.  The A/B notation is, respectively, the strike price of each trade. The first 'leg' of the strategy, corresponding to B, is the sale of a call option at a strike price of B (in this case $165).  The proceeds from this sale, after transaction costs, are generally used to offset the cost of the second 'leg'. The second 'leg' of the strategy, corresponding to A, is the purchase of a call option at a strike price of A (in this case $145). Now, the important part: the payoff.  You can visualize it as so. This is where it gets a teeny bit math-y.  Below, P is the profit of the strategy, K1 is the strike price of the long call, K2 is the strike price of the short call, T1 is the premium paid for the long call option at the time of purchase, T2 is the premium received for the short call at the time of sale, and S is the current price of the stock.  For simplicity's sake, we will assume that your position quantity is a single option contract and transaction costs are zero (which they are not). P = (T2 - max(0, S - K2)) + (max(0, S - K1) - T1) Concretely, let's plug in the strikes of the strategy Nathan proposes, and current prices (which I pulled from the screen).  You have: P = (1.85 - max(0, 142.50 - 165)) - (max(0, 142.50 - 145)) = -$7.80 If the stock goes to $150, the payoff is -$2.80, which isn't quite break even -- but it may have been at the time he was speaking on TV. If the stock goes to $165, the payoff is $12.20. Please do not neglect the cost of the trades!  Trading options can be pretty expensive depending on the broker.  Had I done this trade (quantity 1) at many popular brokers, I still would've been net negative PnL even if NFLX went to >= $165. I don't have a direct short position. It is a structured product linked to the performance of Tesla. I basically get a fixed coupon payment every quater and as long as Tesla doesn't move up more than 50% in the next half year I get my initial investment back plus the coupons. If it should move up more than 50% I lose that percentage of my initial investment "Seems like you are concerned with something called assignment risk. It's an inherent risk of selling options: you are giving somebody the right, but not the obligation, to sell to you 100 shares of GOOGL. Option buyers pay a premium to have that right - the extrinsic value. When they exercise the option, the option immediately disappears. Together with it, all the extrinsic value disappears. So, the lower the extrinsic value, the higher the assignment risk. Usually, option contracts that are very close to expiration (let's say, around 2 to 3 weeks to expiration or less) have significantly lower extrinsic value than longer option contracts. Also, generally speaking, the deeper ITM an option contract is, the lower extrinsic value it will have. So, to reduce assignment risk, I usually close out my option positions 1-2 weeks before expiration, especially the contracts that are deep in the money. edit: to make sure this is clear, based on a comment I've just seen on your question. To ""close out an options position"", you just have to create the ""opposite"" trade. So, if you sell a Put, you close that by buying back that exact same put. Just like stock: if you buy stock, you have a position; you close that position by selling the exact same stock, in the exact same amount. That's a very common thing to do with options. A post in Tradeking's forums, very old post, but with an interesting piece of data from the OCC, states that 35% of the options expire worthless, and 48% are bought or sold before expiration to close the position - only 17% of the contracts are actually exercised! (http://community.tradeking.com/members/optionsguy/blogs/11260-what-percentage-of-options-get-exercised) A few other things to keep in mind: certain stocks have ""mini options contracts"", that would correspond to a lot of 10 shares of stock. These contracts are usually not very liquid, though, so you might not get great prices when opening/closing positions you said in a comment, ""I cannot use this strategy to buy stocks like GOOGL""; if the reason is because 100*GOOGL is too much to fit in your buying power, that's a pretty big risk - the assignment could result in a margin call! if margin call is not really your concern, but your concern is more like the risk of holding 100 shares of GOOGL, you can help manage that by buying some lower strike Puts (that have smaller absolute delta than your Put), or selling some calls against your short put. Both strategies, while very different, will effectively reduce your delta exposure. You'd get 100 deltas from the 100 shares of GOOGL, but you'd get some negative deltas by holding the lower strike Put, or by writing the higher strike Call. So as the stock moves around, your account value would move less than the exposure equivalent to 100 shares of stock." "The formula you are looking for is pretty complicated. It's given here: http://itl.nist.gov/div898/handbook/eda/section3/eda3661.htm You might prefer to let somebody else do the grunt work for you. This page will calculate the probability for you: http://stattrek.com/online-calculator/normal.aspx. In your case, you'd enter mean=.114, standard deviation=.132, and ""standard score""= ... oh, you didn't say what you're paying on your debt. Let's say it's 6%, i.e. .06. Note that this page will give you the probability that the actual number will be less than or equal to the ""standard score"". Enter all that and click the magic button and the probability that the investment will produce less than 6% is ... .34124, or 34%. The handy rule of thumb is that the probability is about 68% that the actual number will be within 1 standard deviation of the mean, 95% that it will be within 2 standard deviations, and 99.7% that it will be within 3. Which isn't exactly what you want because you don't want ""within"" but ""less than"". But you could get that by just adding half the difference from 100% for each of the above, i.e. instead of 68-95-99.7 it would be 84-98-99.9. Oh, I missed that in a follow-up comment you say you are paying 4% on a mortgage which you are adjusting to 3% because of tax implications. Probability based on mean and SD you gave of getting less than 3% is 26%. I didn't read the article you cite. I assume the standard deviation given is for the rate of return for one year. If you stretch that over many years, the SD goes down, as many factors tend to even out. So while the probability that money in a given, say, mutual fund will grow by less than 3% in one year is fairly high -- the 25 - 35% we're talking here sounds plausible to me -- the probability that it will grow by an average of less than 3% over a period of 10 or 15 or 20 years is much less. Further Thought There is, of course, no provably-true formula for what makes a reasonable risk. Suppose I offered you an investment that had a 99% chance of showing a $5,000 profit and a 1% chance of a $495,000 loss. Would you take it? I wouldn't. Even though the chance of a loss is small, if it happened, I'd lose everything I have. Is it worth that risk for the modest potential profit? I'd say no. Of course to someone who has a billion dollars, this might be a very reasonable risk. If it fails, oh well, that could really cut in to what he can spend on lunch tomorrow." as no advantage from exerting American call option early,we can use Black schole formula to evaluate the option.However, American put option is more likely to be exercised early which mean Black schole does not apply for this style of option Yes. There are levels of option trading permission. For example, I've never set myself up for naked put writing.  But, if you already have the call spread, buying back the shorted call will leave you with a long call. This wouldn't be an issue. As long as you have the cash/margin to buy back that higher strike call. The mathematics make it easier to understand why this is the case. Using very bad shorthand, d1 and d2 are inputs into N(), and N() can be expressed as the probability of the expected value or the most probable value which in this case is the discounted expected stock price at expiration. d1 has two σs which is volatility in the numerator and one in the denominator.  Cancelling leaves one on top.  Calculating when it's infinity gives an N() of 1 for S and 0 for K, so the call is worth S and the put PV(K).  At 0 for σ, it's the opposite. More concise is that any mathematical moment be it variance which mostly influences volatility, mean which determines drift, or kurtosis which mostly influences skew are all uncertanties thus costs, so the higher they are, the higher the price of an option. Economically speaking, uncertainties are costs.  Since costs raise prices, and volatility is an uncertainty, volatility raises prices. It should be noted that BS assumes that prices are lognormally distributed.  They are not.  The closest distribution, currently, is the logVariance Gamma distribution. "Yes this is possible in the most liquid securities, but currently it would take several days to get filled in one contract at that amount There are also position size limits (set by the OCC and other Self Regulatory Organizations) that attempt to prevent people from cornering a market through the options market. (getting loads of contacts without effecting the price of the underlying asset, exercising those contracts and suddenly owning a huge stake of the asset and nobody saw it coming - although this is still VERY VERY possible) So for your example of an option of $1.00 per contract, then the position size limits would have prevented 100 million of those being opened (by one person/account that is). Realistically, you would spread out your orders amongst several options strike prices and expiration dates. Stock Indexes are some very liquid examples, so for the Standard & Poors you can open options contracts on the SPY ETF, as well as the S&P 500 futures, as well as many other S&P 500 products that only trade options and do not have the ability to be traded as the underlying shares. And there is also the saying ""liquidity begets liquidity"", meaning that because you are making the market more liquid, other large market participants will also see the liquidity and want to participate, where they previously thought it was too illiquid and impossible to close a large position quickly" Firstly, going short on a stock and worrying if the price suddenly gaps up a lot due to good news is the same as being long on a stock and worrying that the price will suddenly collapse due to bad news. Secondly, an out of the money call option would be cheaper than an in the money call option, in fact the further out of the money the cheaper the premium will be, all other things being equal. So a good risk management strategy would be to set your stop orders as per your trading plan and if you wish to have added protection in case of a large gap is to buy a far out of the money call option. The premium should not be too expensive. Something you should also consider is the time until expiry for the option, if your time frame for trading is days to weeks you make consider a cheaper option that expires in about a month, but if you are planning on holding the position for more than a month you might need a longer expiry period on the option, which will increase the premium. Another option to consider, if your broker offers it, is to use a guaranteed stop loss order. You will pay a little premium for this type of order and not all brokers offer it, but if it is offered you will be protected against any price gaps past your guaranteed stop loss price. I think George's answer explains fairly well why the brokerages don't allow this - it's not an exchange rule, it's just that the brokerage has to have the shares to lend, and normally those shares come from people's margin, which is impossible on a non-marginable stock. To address the question of what the alternatives are, on popular stocks like SIRI, a deep In-The-Money put is a fairly accurate emulation of an actual short interest.  If you look at the options on SIRI you will see that a $3 (or higher) put has a delta of -$1, which is the same delta as an actual short share. You also don't have to worry about problems like margin calls when buying options.  The only thing you have to worry about is the expiration date, which isn't generally a major issue if you're buying in-the-money options... unless you're very wrong about the direction of the stock, in which case you could lose everything, but that's always a risk with penny stocks no matter how you trade them. At least with a put option, the maximum amount you can lose is whatever you spent on the contract.  With a short sale, a bull rush on the stock could potentially wipe out your entire margin.  That's why, when betting on downward motion in a microcap or penny stock, I actually prefer to use options.  Just be aware that option contracts can generally only move in increments of $0.05, and that your brokerage will probably impose a bid-ask spread of up to $0.10, so the share price has to move down at least 10 cents (or 10% on a roughly $1 stock like SIRI) for you to just break even; definitely don't attempt to use this as a day-trading tool and go for longer expirations if you can. Yes, and there's a good reason they might. (I'm gonna use equity options for the example; FX options are my thing, but they typically trade European style). The catch is dividends.  Imagine you're long a deep-ITM call on a stock that's about to pay a dividend. If that dividend is larger than the time value remaining on the option, you'd prefer to exercise early - giving you the stock and the dividend payment - rather than hanging on to the time value of the option.  You can get a similar situation in FX options when you're long a deep-ITM American call on a positive-carry currency (say AUDJPY); you might find yourself so deep in the money, with so little time value left on the option, that you'd rather exercise the option and give up the remaining time value in return for the additional carry from getting the spot position early. These are the steps I'd follow: $200 today times (1.04)^10 = Cost in year 10.  The 6 deposits of $20 will be one time value calculation with a resulting year 7 final value. You then must apply 10% for 3 years (1.1)^3 to get the 10th year result.  You now have the shortfall. Divide that by the same (1.1)^3 to shift the present value to start of year 7. (this step might confuse you?) You are left with a problem needing 3 same deposits, a known rate, and desired FV. Solve from there.  (Also, welcome from quant.SE. This site doesn't support LATEX, so I edited the image above.) If you are in the money at expiration you are going to get assigned to the person on the other side of the contract. This is an extremely high probability. The only randomness comes from before expiration. Where you may be assigned because a holder exercised the option before expiration, this can unbalance some of your strategies. But in exchange, you get all the premium that was still left on the option when they exercised. An in the money option, at expiration, has no premium. The value of your in the money option is Current Stock price - Strike Price, for a call. And Strike price - Current Stock price, for a put. Thats why there is no free lunch in this scenario. "The shares available to short are a portion of those shares held by the longs. This number is actually much easier to determine outside of active trading hours, but either way doesn't really impact the matter at hand since computers are pretty good at counting things. If your broker is putting up obstacles to your issuing sell short limit orders in the pre-market then there is likely some other reason (maybe they reserve that function to ""premium"" account holders?)"