What Is a Margin Account and How Does It Work?

A margin account is a brokerage account that lets you borrow money from your broker to purchase securities, using the assets in your account as collateral. Unlike a cash account where you can only trade with settled funds you've deposited, a margin account provides leverage — typically allowing you to borrow up to 50% of the purchase price of most stocks under Federal Reserve Regulation T. This means with $10,000 in your account, you could potentially buy up to $20,000 worth of securities.

The borrowed funds come with an interest charge, called the margin rate, which varies by broker and account size. Major brokers like Interactive Brokers, Fidelity, and Charles Schwab publish tiered rate schedules where larger balances qualify for lower rates. As of 2024, margin rates typically range from around 8% to 13% annually for retail investors, though they fluctuate with the federal funds rate. Interest accrues daily and is charged monthly to your account.

Initial and Maintenance Margin Requirements

Two key regulatory thresholds govern margin accounts. The initial margin requirement, set at 50% by Regulation T, determines how much you can borrow when opening a new position. If you want to buy $10,000 of stock, you must have at least $5,000 of your own equity in the account.

The maintenance margin requirement is the minimum equity you must maintain after the trade is established. FINRA sets this at 25% of the total market value of margin securities, though most brokers impose higher house requirements — often 30% to 40% for concentrated positions or volatile stocks. If your account equity falls below this threshold due to market declines, you'll receive a margin call requiring you to deposit additional cash or securities, or sell positions to bring the account back into compliance.

For example, if you buy $20,000 of stock with $10,000 borrowed and $10,000 of your own money, and the stock drops 30% to $14,000, your equity is now $4,000 ($14,000 value minus $10,000 loan). That's 28.6% equity — above FINRA's 25% minimum but potentially below your broker's 30% house requirement, triggering a margin call.

Margin Calls: Types and Consequences

Margin calls come in three forms, each with different urgency and consequences:

  • Regulation T calls occur when you don't meet the 50% initial requirement at trade time. You must deposit funds within two business days (T+2) or the broker will liquidate positions.
  • Maintenance calls happen when account equity falls below the maintenance threshold. Brokers typically give 2-5 business days to meet the call, but can liquidate immediately if the shortfall is severe or markets are volatile.
  • House calls reflect your broker's stricter internal requirements. These vary by firm and security type — concentrated positions, penny stocks, and leveraged ETFs often carry 50% to 100% maintenance requirements.

If you fail to meet a margin call, your broker has the right to sell any securities in your account without prior notice to cover the deficiency. This forced liquidation can lock in losses at the worst possible prices and may generate taxable events. The broker chooses which positions to sell, not you.

Pattern Day Trading Rules and Portfolio Margin

If you execute four or more day trades within five business days in a margin account, and those trades represent more than 6% of your total trading activity, FINRA designates you as a pattern day trader (PDT). This classification requires maintaining a minimum of $25,000 in account equity at all times. If your balance drops below $25,000, you'll lose margin buying power and may be restricted to cash-account trading for 90 days.

Experienced investors with $100,000+ in equity may qualify for portfolio margin, a risk-based margining system that calculates requirements based on the overall risk of your entire portfolio rather than position-by-position rules. Portfolio margin can significantly reduce capital requirements for hedged positions — for example, a long stock position paired with protective puts — but requires passing a suitability test and maintaining higher minimum equity.

Practical Considerations Before Opening a Margin Account

Before enabling margin, evaluate whether the benefits align with your strategy and risk tolerance. Margin makes sense for:

  • Short-term opportunistic trades where you expect quick price movements and can repay the loan rapidly, minimizing interest costs.
  • Bridging settlement gaps — using margin to buy a new position before a sale settles, avoiding good-faith violations in a cash account.
  • Tax-loss harvesting — selling a losing position and immediately buying a similar (but not substantially identical) security without waiting for cash settlement.

Margin is dangerous for long-term buy-and-hold investors. The interest drag compounds against you over time, and a prolonged bear market can trigger margin calls that force sales at market bottoms. If you do use margin, consider these safeguards:

  • Borrow well below the maximum — many experienced traders limit margin usage to 20-30% of account value.
  • Maintain a cash buffer or readily liquid assets to meet potential calls without forced selling.
  • Set personal stop-loss levels well above the broker's maintenance requirement.
  • Monitor your account daily during volatile periods; margin calls can escalate quickly.

Finally, understand the tax implications. Margin interest is deductible as investment interest expense only if you itemize deductions and have net investment income, and only up to the amount of that income. The deduction is claimed on Form 4952 and carried forward if unused. Consult a tax professional for your specific situation.

A margin account is a powerful tool that amplifies both gains and losses. Used disciplinedly with strict risk controls, it can enhance returns and provide liquidity flexibility. Used recklessly, it can destroy an account in days. Know the rules, respect the math, and never borrow more than you can afford to repay immediately if the market turns against you.