Margin Account: Borrowing Against Securities
For educational purposes only; not investment advice.
Direct answer
Section titled “Direct answer”A margin account lets an eligible investor borrow from a broker using securities and cash in the account as collateral. The borrowed money can increase buying power, but it also magnifies losses, creates interest cost, and gives the broker contractual rights to protect its loan.
The important point is that margin is not free extra capital. It is debt secured by marketable assets whose prices can change quickly. If account equity falls below requirements, the broker may restrict the account or sell securities, sometimes without waiting for the customer to deposit money.
Mechanism
Section titled “Mechanism”The core relationship is:
Account equity = market value of securities − margin loan balance
Equity percentage = account equity ÷ market value of securities
Initial margin determines how much equity is needed to open a position. Maintenance margin determines the minimum equity needed to keep it. Brokers may set house requirements above regulatory minimums, and requirements can differ by security, concentration, volatility, price, liquidity, and account strategy.
Interest accrues on the debit balance. Buying power, cash, settled cash, margin excess, and withdrawal capacity are broker-defined fields; they are not interchangeable. A sale can create visible cash while the account still has settlement, loan, or requirement constraints.
Example
Section titled “Example”An investor deposits $10,000, borrows $10,000, and buys $20,000 of stock.
If the stock rises 20%, market value becomes $24,000. After repaying the unchanged $10,000 loan, equity is $14,000, a 40% gain on the original equity before interest.
If the stock falls 20%, market value becomes $16,000. Equity is $6,000, a 40% loss before interest.
If maintenance margin is 30%, the simplified trigger value with a $10,000 loan is:
$10,000 ÷ (1 − 30%) ≈ $14,286
Below that approximate value, equity is less than 30% of the position. Real accounts can have multiple securities, changing requirements, accrued interest, and broker-specific calculations.
- Amplified losses: price changes act on borrowed exposure but losses reduce the investor’s equity.
- Forced liquidation: the broker may choose what to sell and when.
- No guaranteed cure period: a margin call does not guarantee time to deposit funds.
- Interest-rate risk: margin rates can change and continue accruing even if the position is flat or down.
- House requirement risk: a broker can raise requirements for concentrated or volatile positions.
- Gap risk: overnight news can move prices through trigger levels.
- Loss beyond deposit: severe moves, short positions, or liquidation deficits can leave a remaining debt.
Common misconceptions
Section titled “Common misconceptions”“Opening a margin account means I must borrow.” Not necessarily. The account type permits borrowing, but an actual debit balance depends on transactions.
“A margin call always gives me time.” Broker agreements often allow immediate liquidation.
“Regulatory minimums are the broker’s exact requirements.” Brokers can impose stricter house and security-specific requirements.
“Dividends can safely pay the interest.” Dividends can be cut, interest can rise, and price losses can dominate both.
Related topics
Section titled “Related topics”Sources
Section titled “Sources”- SEC: investor bulletin on margin accounts, margin calls, and broker liquidation rights.
- FINRA: investor education on borrowing to invest and margin risk.
- Federal Reserve: Regulation T background for broker-dealer credit.