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In finance, a margin is a collateral that the holder of a position in securities, options, or futures contracts has to deposit to cover the credit risk of his counterparty (most often his broker). This risk can arise if the holder has done any of the following:

  • borrowed cash from the counterparty to buy securities or options,
  • sold securities or options short, or
  • entered into a futures contract.

The collateral can be in the form of cash or securities, and it is deposited in a margin account. On U.S. futures exchanges, "margin" was formally called performance bond.


Margin buying


Jane buys a share in a company for $100, using $20 of her own money, and $80 borrowed from her broker. The net value (share - loan) is $20. The broker wants a minimum margin requirement of $10.

Suppose the share goes down to $85. The net value is now only $5 (net value ($20) - share loss of ($15)), and Jane will either have to sell the share or repay part of the loan (so that the net value of her position is again above $10).

Margin buying is buying securities with cash borrowed from a broker, using other securities as collateral. This has the effect of magnifying any profit or loss made on the securities. The securities serve as collateral for the loan. The net value, i.e. the difference between the value of the securities and the loan, is initially equal to the amount of one's own cash used. This difference has to stay above a minimum margin requirement, the purpose of which is to protect the broker against a fall in the value of the securities to the point that the investor can no longer cover the loan.

In the 1920s, margin requirements were loose. In other words, brokers required investors to put in very little of their own money. Whereas today, the Federal Reserve's margin requirement limits debt to 50 percent, during the 1920s leverage rates of up to 90 percent debt were not uncommon.[1] When the stock market started to contract, many individuals received margin calls. They had to deliver more money to their brokers or their shares would be sold. Since many individuals did not have the equity to cover their margin positions, their shares were sold, causing further market declines and further margin calls. This was one of the major contributing factors which led to the Stock Market Crash of 1929, which in turn contributed to the Great Depression [1], a troubling financial time in the 1930s. However, as reported in Peter Rappoport and Eugene N. White's 1994 paper Was the Crash of 1929 Expected[2], all sources indicate that beginning in either late 1928 or early 1929, "margin requirements began to rise to historic new levels. The typical peak rates on brokers' loans were 40-50 percent. Brokerage houses followed suit and demanded higher margin from investors."

Types of margin requirements


Current liquidating margin

The current liquidating margin is the value of a securities position if the position were liquidated now. In other words, if the holder has a short position, this is the money needed to buy back; if he is long, it is the money he can raise by selling it.

Variation margin

The variation margin or maintenance margin is not collateral, but a daily offsetting of profits and losses. Futures are marked-to-market every day, so the current price is compared to the previous day's price. The profit or loss on the day of a position is then paid to or debited from the holder by the futures exchange. This is possible, because the exchange is the central counterparty to all contracts, and the number of long contracts equals the number of short contracts. Certain other exchange traded derivatives, such as options on futures contracts, are marked-to-market in the same way.

Premium margin

The seller of an option has the obligation to deliver the underlying of the option if it is exercised. To ensure he can fulfil this obligation, he has to deposit collateral. This premium margin is equal to the premium that he would need to pay to buy back the option and close out his position.

Additional margin

Additional margin is intended to cover a potential fall in the value of the position on the following trading day. This is calculated as the potential loss in a worst-case scenario.

Minimum margin requirement

The minimum margin requirement is now the sum of these different types of margin requirements. The margin (collateral) deposited in the margin account has to be at least equal to this minimum. If the investor has many positions with the exchange, these margin requirements can simply be netted.

Example 1
An investor sells a call option, where the buyer has the right to buy 100 shares in Universal Widgets S.A. at 90¢. He receives an option premium of 14¢. The value of the option is 14¢, so this is the premium margin. The exchange has calculated, using historical prices, that the option value won't go above 17¢ the next day, with 99% certainty. Therefore, the additional margin requirement is set at 3¢, and the investor has to post at least 14¢ + 3¢ = 17¢ in his margin account as collateral.
Example 2
Futures contracts on sweet crude oil closed the day at $65. The exchange sets the additional margin requirement at $2, which the holder of a long position pays as collateral in his margin account. A day later, the futures close at $66. The exchange now pays the profit of $1 in the mark-to-market to the holder. The margin account still holds only the $2.
Example 3
An investor is long 50 shares in Universal Widgets Ltd, trading at 120 pence (£1.20) each. The broker sets an additional margin requirement of 20 pence per share, so £10 for the total position. The current liquidating margin is currently £60 in favour of the investor. The minimum margin requirement is now -£60 + £10 = -£50. In other words, the investor can run a deficit of £50 in his margin account and still fulfil his margin obligations. This is the same as saying he can borrow up to £50 from the broker.

Initial and maintenance margin requirements

The initial margin requirement is the amount required to be collateralized in order to open a position. Thereafter, the amount required to be kept in collateral until the position is closed is the maintenance requirement. The maintenance requirement is the minimum amount to be collateralized in order to keep an open position. It is generally lower than the initial requirement. This allows the price to move against the margin without forcing a margin call immediately after the initial transaction. On instruments determined to be especially risky, however, the regulators, the exchange, or the broker may set the maintenance requirement higher than normal or equal to the initial requirement to reduce their exposure to the risk accepted by the trader.

Margin call

When the margin posted in the margin account is below the minimum margin requirement, the broker or exchange issues a 'margin call. The investors now either have to increase the margin that they have deposited or close out their position. They can do this by selling the securities, options or futures if they are long and by buying them back if they are short. But if they do none of these, then the broker can sell his securities to meet the margin call.

Price of Stock for Margin Calls

The minimum margin requirement, sometimes called the maintenance margin requirement, is the ratio set for:

  • (Stock Equity - Leveraged Dollars) to Stock Equity
  • Stock Equity being the stock price * no. of stocks bought and Leveraged Dollars being the amount borrowed in the margin account.
  • E.g. An investor bought 1000 shares of ABC company each priced at $50. If the initial margin requirement were 60%:
  • Stock Equity: $50 * 1000 = $50,000
  • Leveraged Dollars or amount borrowed: ($50 * 1000)* (1-60%) = $20,000

So the maintenance margin requirement uses the above variables to form a ratio that investors have to abide by in order to keep the account active.

The point is, let's say the maintenance margin requirement is 25% - That means customer has to maintain Net Value equal to 25% of the total stock equity. That means he has to maintain net equity of $50,000 * 0.25 = $12,500. So at what price would the investor be getting a margin call? Let P be the price, so 1000P in our case is the Stock Equity.

  • (Stock Equity - Leveraged Dollars) divided by Stock Equity = 25%
  • (1000P - $20,000)/1,000P = 0.25
  • (1000P - $20,000) = 250P
  • 1000P = 250P + $20,000
  • 750P = $20,000
  • P = $20,000/750 = $26.67 / share

So if the stock price drops from $50 to $26.67, investors will be called to add additional funds to the account to make up for the loss in stock equity.

Reduced margins

Margin requirements are reduced for positions that offset each other. For instance spread traders who have offsetting futures contracts do not have to deposit collateral both for their short position and their long position. The exchange calculates the loss in a worst case scenario of the total position.

Margin-equity ratio

Margin-equity ratio is a term used by speculators, representing the amount of their trading capital that is being held as margin at any particular time. Traders would rarely (and unadvisedly) hold 100% of their capital as margin. The probability of losing their entire capital at some point would be high. By contrast, if the margin-equity ratio is so low as to make the trader's capital equal to the value of the futures contract itself, then they would not profit from the inherent leverage implicit in futures trading. A conservative trader might hold a margin-equity ratio of 15%, while a more aggressive trader might hold 40%.

Return on margin

Return on margin (ROM) is often used to judge performance because it represents the net gain or net loss compared to the exchange's perceived risk as reflected in required margin. ROM may be calculated (realized return) / (initial margin). The annualized ROM is equal to

(ROM + 1)(year/trade_duration) - 1

For example if a trader earns 10% on margin in two months, that would be about 77% annualized

(ROM +1)1/6 - 1 = 0.1 thus ROM = 1.16 - 1

Sometimes, Return on Margin will also take into account peripheral charges such as brokerage fees and interest paid on the sum borrowed. The margin interest rate is usually based on the Broker's call.


  1. ^ a b Cundiff, Kirby R. (January 2007). "Monetary-Policy Disasters of the Twentieth Century". The Freeman Online. Retrieved 10Feb2009. 
  2. ^ Rappoport, Peter; White, Eugene N. (March 1994). "Was the Crash of 1929 Expected". The American Economic Review (United States: American Economic Association) 84 (1): 271–281. Retrieved 10Feb2009. 

See also


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