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:
That is the maintenance margin required for that position.  Whenever you trade using your margin account, you must (by law, and also separately often by stricter policies from the brokerage) have a certain percentage of equity - at least 25%, often higher.  That protects the brokerage from significant losses if your position drops in value significantly (hopefully preventing the brokerage from failing outright in the event of a major collapse).  If the amount of equity falls below the maintenance requirement, you will have a margin call and be required to put some cash (or equity) into the account to maintain that level. See Maintenance Margin definition on Investopedia for more information. 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. Depends on the stock involved, but for the most part brokerages allow you gain entry at 50%, meaning you can short twice the cash on hand you have.   Going forward, you need to maintain 30%, so on a $10,000 short, you'd have to maintain $3000 in your account. Example, an account with $5000 cash - You can short $10,000 securities.  Let say 100 shares of xyz at $100 per share. After trade settles, you won't receive a margin call until your balance falls to $3000, probably right around the time xyz rises to $120 per share.  Riskier stocks will have higher margin maintenance requirements - leveraged vehicles like FAS/FAZ (triple leveraged) require 90% margin (3x30%) if they are allowed to be 'shorted' at all. As the referenced document says, there are 3 formulas, and you need to use the formula which results the greatest margin requirement. In your case, you need to use the 10% formula: "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." I cannot believe noone mentioned this so far: Every decision you make is independent from previous decisions (that is, if you only care about your expected gain). This means that your decision whether to buy the option should be the same whether you bought the same option before or not. "Number 2 cannot occur. You can buy the call back and sell the stock, but the broker won't force that #2 choice. To trade options, you must have a margin account. No matter how high the stock goes, once ""in the money"" the option isn't going to rise faster, so your margin % is not an issue.  And your example is a bit troublesome to me. Why would a $120 strike call spike to $22 with only a month left? You've made the full $20 on the stock rise and given up any gain after that. That's all. The call owner may exercise at any time. Edit: @jaydles is right, there are circumstances where an option price can increase faster than the stock price. Options pricing generally follows the Black-Scholes model. Since the OP gave us the current stock price, option strike price, and time to expiration, and we know the risk free rate is <1%, you can use the calculator to change volatility. The number two scenario won't occur, however, because a covered call has no risk to the broker, they won't force you to buy the option back, and the option buyer has no motive to exercise it as the entire option value is time premium." Oh really. I will have to check into that. It would be a bummer if that is the case. Something I will need to look into. If you don't need margin and are not trading the underlying asset (which I could see being a problem), then I don't see what the problem is. But I shall see. Thanks. If one wants to have a bound on the loss percentages that are acceptable, this is would be a way to enforce that. For example, suppose someone wants to have a 5% stop-loss but doesn't want this to be worse than 10% as if the stock goes down more than 10% then the sell shouldn't happen. Thus, if the stock opened in a gap down 15% one day, this triggers the stop-loss and would exit at too low of a price as the gap was quite high as I wonder how familiar are you with how much a stock's price could change that makes the prices not be as continuous as one would think. At least this would be my thinking on a volatile stock where one may want to try to limit losses if the stock does fall within a specific range. Ok, so disregarding passivity, could you help me through a simplified example?   Say I only had two assets, SPY and TLT, with a respective weight of 35 and 65% and I want want to leverage this to 4x.  Additionally, say daily return covar is:  * B/B .004% * B/S -.004% * S/S .02%   Now, if I read correctly, I should buy ATM calls xxx days in the future.  Which may look like: Ticker, S, K, Option Price, Delta, Lambda  * TLT  $126.04  $126.00  $4.35  0.50  14.5 * SPY  $134.91  $134.00  $6.26  0.55  11.8  ^ This example is pretty close but some assets are far off.   I feel like I'm on the wrong track so I'll stop here.    I just want to lever up my risk-parity. Margin rates are too high and I'm docked by Reg-T. "Some investors worry about interest rate risk because they Additional reason is margin trading which is borrowing money to invest in capital markets. Since margin trading includes minimum margin requirements and maintenance margin to protect lender ""such as a broker""  , a decrease in the value of bonds might trigger a threat of a margin call There are other reasons why investors care about interest rate risk  such as spread trade investors who benefit from difference in short term/ long term interest rates. Such investors borrow short term loans -which enables them to pay low interest- and lend long term loans - which enables them to gain high interest-. Any disturbance between the interest rate spread between short term and long term bonds might affect investor's profit and might even lead to losses. In summary , it all depends on you investment objective and financial condition. You should consult with your financial adviser to help plan for your financial goals." In the equity world, if a stock trades at 110 and is going to pay a dividend of 10 in a few days, an option expiring after the ex date would take the dividend into account and would trade as if the stock were trading at 100. (Negative) interest rates may also lead to a similar effect. In the commodity world the cost of carry needs to be taken into account. One reason might be the 100% margin requirement on long options.  Suppose I want to go long AAPL.   I could get a deep ITM call or buy shares. $12,700 for 100 shares, with it's 25% margin requirement is like around $3200 locked up cash.  Combine with a deep OTM Jan 2017 $70 strike put for $188, would give a $3400 margin requirement to enter the trade. or I could be in the JAN 2017 $70 strike for nearer $5800, but with a 100% margin requirement due to being a long call. So (3400/5800) = 59% increase in margin requirement for Deep ITM calls. Plus long term the shares will pay dividends, while a LEAP CALL does not. On July 20, when you posted this question, AAPL was trading almost at 115.  The market charges an extra premium for buying an option that is in the money (or on the money like this case) over one that is out of the money.  In order for the 130 Call to be worth something the market has to go up 15 points. Otherwise you lose 100% of your premium. On the other hand with the 115 every point that the market goes up means that you recover some of that premium. It is much more likely that you recover part of your premium with the 115 than with the 130.  With the higher probability of losing part of the premium, the sellers are going to be reluctant to write the option unless they receive larger compensation. This is dependent on the broker according to The Options Industry Council.  Your broker will specify what they would do upon expiry (or hours before last trade) if you did not indicate your preference. Most likely they will conduct a probabilistic simulation to see whether exercising the contracts may result in margin deficit even after selling the delivered shares under extreme circumstances. In most cases, brokers tend to liquidate the option for you (sell to close) before expiry.  I've seen people complain about certain brokers forcing liquidation at terrible bid-ask spreads even though the options are still days to expiry. It is better for you to close the position on your own beforehand. The best brokers would allow margin deficit and let you deposit the required amount of money afterward.  Please consult your broker's materials. If you can't find them, use live chat or email tickets.