What it means
When you open a margin account, the broker agrees to lend you part of the purchase price of shares or other securities. You put up your own money, called equity, and borrow the rest.
The securities you buy become security for the loan, and you pay interest on the borrowed amount for as long as it is outstanding. Rules limit how much can be borrowed.
Regulators and brokers set an initial margin requirement, often around half of the purchase price for shares, and a maintenance margin, which is the minimum equity percentage you must keep afterwards. Brokers can set stricter requirements for volatile or thinly traded securities.
The danger is leverage. A 20% fall in the price of a position bought with half borrowed money wipes out 40% of the investor's equity.
If the equity percentage drops below the maintenance level, the broker issues a margin call, asking for more cash or securities within a short time. If the investor does not respond, the broker can sell holdings without asking, and it can choose which ones.
Forced selling often happens at the worst moment, when prices have already fallen. The investor remains responsible for any shortfall if the sale proceeds do not cover the loan.
Aggregate margin debt across a market is also watched by analysts as a sentiment indicator. Rising totals suggest growing risk appetite and may signal excess optimism, while sharp falls can reflect forced selling or caution.
It is a clue, not a forecast, and it should be read with other data. Interest costs deserve attention too.
The rate is usually tied to a benchmark plus a margin set by the broker, and larger balances often earn lower rates, so the true cost of leverage depends on the account size and the lender.
In practice
Real-world examples.
Example
A trader with $40,000 buys $80,000 of shares in a technology company on margin. When the shares rise 10%, her equity rises by $8,000, a 20% return on her own money, though a 10% fall would have cost her the same amount. She reviews the account every day while the position is open.
Example
An investor takes a margin loan to buy shares ahead of an expected rise. A sharp market fall triggers a margin call, and he has to deposit cash or sell holdings at depressed prices. The loss on the sale is larger than the fall in the market.
Example
A wealthy client uses a margin loan against a diversified portfolio to fund a house deposit instead of selling shares and paying tax. She pays interest on the loan and keeps a large cushion of equity to avoid forced sales. The interest cost is lower than the tax she would have paid on selling.
Formula
Calculation
Margin debt = Purchase value - Investor's own equity
Equity percentage = (Market value - Margin debt) / Market value
An investor buys $100,000 of shares using $50,000 of her own money and a $50,000 margin loan. At an illustrative interest rate of 8% a year, the annual interest is $50,000 x 0.08 = $4,000. If the shares fall to $70,000, her equity is $70,000 - $50,000 = $20,000, and the equity percentage is $20,000 / $70,000 = 28.6%. If they fall to $60,000, equity is $10,000 and the percentage is $10,000 / $60,000 = 16.7%, which is below a 25% maintenance requirement, so a margin call follows.Case study
Seen in the real world.
Kestrel Trading is an illustrative, fictional small firm whose owner bought $400,000 of shares using $200,000 of his own money and $200,000 of margin debt. The portfolio was concentrated in two shares in the same sector.
When the sector fell 35% in a few weeks, the portfolio value dropped to $260,000, leaving equity of only $60,000, or about 23%. The broker issued a margin call, and the owner had to sell one of the holdings at a loss to meet it.
In this illustrative story, the later recovery in prices did not help because the shares had already been sold. The owner afterwards cut his borrowing to a quarter of the portfolio value and spread the holdings more widely.
Watch out
Common mistakes.
- Believing that a loss is limited to the amount invested, when margin losses can exceed the original cash.
- Ignoring interest, which accrues daily and reduces returns, particularly on positions held for a long time.
- Using the maximum borrowing available, which leaves no cushion when prices fall.
Questions
People also ask.
What is a margin call?
It is a demand from the broker to add cash or securities because the account equity has fallen below the maintenance requirement.
Can the broker sell my shares without asking?
Yes, under the margin agreement the broker can usually sell positions without notice to restore the required equity.
Is margin debt tax-deductible?
Treatment depends on the country and the use of the loan, so it should be confirmed with a tax adviser.
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