Margin

Margin is the practice of borrowing money from your brokerage to buy more securities than your cash balance allows, using your existing portfolio as collateral. When you "buy on margin," you're essentially taking out a loan from your broker, and the securities you purchase serve as the loan's collateral. While margin can amplify returns, it also amplifies losses and introduces the risk of forced liquidation through margin calls.

How Margin Works:

Regulation T (set by the Federal Reserve) requires investors to deposit at least 50% of a stock purchase's value — this is the "initial margin." Brokers also require a "maintenance margin" (typically 25%–30% of the position's value) that must be maintained at all times.

Margin Concept	Definition	Typical Requirement
Initial Margin	Minimum deposit to open position	50% (Reg T)
Maintenance Margin	Minimum equity to maintain position	25%–30%
Margin Call	Demand for additional funds	Triggered below maintenance
Buying Power	Total purchasing capacity	2x cash (Reg T)
Margin Interest	Cost of borrowing from broker	6%–13% annually

Margin Example — The Double-Edged Sword:

Starting with $50,000 cash, buying $100,000 of stock on 2:1 margin:

Stock Move	Portfolio Value	Equity	Return on YOUR Capital
+30%	$130,000	$80,000	+60% (2x amplified)
+15%	$115,000	$65,000	+30% (2x amplified)
0%	$100,000	$50,000	0% (minus interest)
-15%	$85,000	$35,000	-30% (2x amplified)
-30%	$70,000	$20,000	-60% (2x amplified)
-50%	$50,000	$0	-100% TOTAL LOSS

The Margin Call — Every Leveraged Investor's Nightmare:

A margin call occurs when your account equity falls below the maintenance margin requirement. When this happens:

1. Broker demands you deposit more cash or securities within 24–72 hours
2. If you can't meet the call, the broker liquidates your positions without your consent
3. Forced liquidation typically occurs at market bottom — the worst possible time to sell
4. You still owe any remaining balance if liquidation doesn't cover the margin loan

Who Uses Margin:

User Type	Purpose	Typical Risk Level
Day Traders	4:1 intraday leverage	Extreme
Swing Traders	2:1 overnight positions	High
Portfolio Managers	Small tactical positions	Moderate
Hedgers	Offset positions with derivatives	Low–Moderate
Most Long-Term Investors	Should NOT use margin	N/A

Margin vs. Other Forms of Leverage:

Feature	Margin	Mortgage	Options
Leverage Ratio	2:1 (Reg T)	4:1 to 19:1	5x–50x+
Margin Call Risk	Yes	No (fixed payments)	No (limited to premium)
Interest Rate	6%–13%	3%–8%	None (premium paid upfront)
Time Pressure	Yes (maintenance req)	No (30-year term)	Yes (expiration date)
Maximum Loss	More than invested	Property value	Premium paid

Warren Buffett's Warning: "It's insane to risk what you have and need for what you don't have and don't need." He considers margin borrowing for individual investors as one of the most dangerous practices in finance, noting that even genius-level investors like Isaac Newton lost fortunes through leveraged speculation.