By Harry Prabandham · Updated September 28, 2026
Investing & Markets
Margin Trading: How Borrowing to Invest Works and What Can Go Wrong
Buying on margin means borrowing from a broker against your securities. It magnifies gains and losses, adds interest, and can force sales.
Margin Trading: How Borrowing to Invest Works and What Can Go Wrong
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What is margin trading?
- Margin trading means borrowing from your brokerage firm to buy securities, using the securities in your account as collateral.
- Leverage magnifies both gains and losses on the amount you invested.
- You pay interest on the loan for as long as it is outstanding.
- You can lose more than the money you deposited.
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Full Guide
What is margin trading?
- Margin trading means borrowing from your brokerage firm to buy securities, using the securities in your account as collateral.
- Leverage magnifies both gains and losses on the amount you invested.
- You pay interest on the loan for as long as it is outstanding.
- You can lose more than the money you deposited.
How much can you borrow?
- Under the Federal Reserve's Regulation T, you can generally borrow up to 50% of the purchase price of marginable stock.
- FINRA Rule 4210 requires equity of at least 25% of the market value of long stock positions, and many firms set higher requirements.
- Firms can raise their requirements at any time, often for volatile or concentrated positions, without advance notice.
- Your equity equals the value of the securities minus what you owe the broker.
What happens in a margin call?
- If your equity falls below the firm's maintenance requirement, the firm can ask you to deposit cash or securities.
- The firm is not required to contact you first and can sell your securities to cover the shortfall.
- You generally cannot choose which securities are sold, and forced sales often happen during market declines.
- Sales triggered by a call can realize taxable gains or lock in losses.
Is margin interest tax-deductible?
- Margin interest used to buy taxable investments may be deductible as investment interest expense if you itemize.
- The deduction is limited to net investment income, with any excess carried forward, and is figured on IRS Form 4952.
- Interest on money borrowed to buy tax-exempt securities is not deductible.
- Margin rates vary by firm and balance and change with short-term interest rates, so compare disclosures before borrowing.
How does short selling use margin?
- Short selling means borrowing shares, selling them, and hoping to buy them back later at a lower price; it requires a margin account.
- Because a stock's price can keep rising, potential losses on a short position have no fixed limit.
- Short sellers owe the lender any dividends paid while the position is open, plus borrowing fees.
- A sharp rally can trigger margin calls and force the short to be closed at a loss.
What are the main risks of borrowing to invest?
- A falling market can trigger margin calls even when you believe a position will recover.
- Interest costs raise the return needed just to break even.
- Margin loans against a single concentrated stock can be especially risky because one price drop hits both the collateral and the loan coverage.
- Securities-based lines of credit carry similar collateral-call risk, even though the money is not used to buy securities.
Key takeaways
- Margin is a loan against your securities that magnifies gains and losses.
- Regulation T and FINRA rules set minimum requirements, and firms can demand more at any time.
- A margin call can force sales without notice, at prices you do not choose.
- Interest is a real cost, and deductibility depends on your tax situation; confirm with a CPA.
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