What Is a Margin Account? How It Works and Key Risks

If you're new to margin, it's easy to see it only as a way to buy more, without realizing how interest charges and forced liquidations really work.

This guide explains initial and maintenance requirements, buying power calculations, key trade-offs compared to cash accounts, and essential risk management strategies.

What Is a Margin Account and How Does It Work?

A margin account functions as a line of credit extended by a brokerage firm. When you open one, the broker allows you to leverage your existing account value to buy more securities than your actual cash balance permits.

The core mechanism relies on collateral and leverage. The cash and eligible securities already sitting in your account serve as collateral for the loan. When you buy a security on margin, you pay for a portion of the purchase with your own capital—known as your equity—and borrow the remaining amount from the broker.

Because margin is a cash loan, brokers charge interest on the borrowed balance. Margin interest is typically calculated daily based on current broker rates and billed to the account monthly. As long as you hold a margin loan balance, interest accrues, raising the total cost of maintaining the position over extended periods.

Key Margin Account Requirements: Initial vs. Maintenance Margin

Trading on margin comes with rules set by regulators and by your broker. Two key numbers decide how much you can borrow and how much of your own money has to stay in the account.

According to Regulation T established by the Federal Reserve Board, traders must deposit at least 50% of the purchase price in equity, while the Financial Industry Regulatory Authority sets a minimum maintenance margin of 25%.

• Initial Margin: The percentage of a security's purchase price that you must pay with your own cash or eligible collateral. Under Federal Reserve Regulation T, the standard initial margin requirement for equities is 50%.
• Maintenance Margin: The minimum percentage of total account value that must consist of your own equity after a position is open. FINRA Rule 4210 sets this minimum at 25%, and according to FINRA investor guidance, many brokerages enforce stricter "house requirements," often in the 30% to 40% range.
• Minimum Margin Equity: Under FINRA rules, you generally need at least $2,000 in equity (or 100% of the purchase price, whichever is less) in your account before you can buy on margin. Some brokerages require more.

Example Scenario: Purchasing Stock on Margin

Imagine you want to purchase $10,000 worth of stock. Under a 50% initial margin requirement, you deposit $5,000 in cash, and borrow the remaining $5,000 from your broker. Your initial account equity is 50%.

If the total market value of the stock falls to $6,000, your loan balance remains $5,000. Your remaining account equity drops to $1,000 ($6,000 market value minus $5,000 loan balance). In this scenario, your equity percentage is roughly 16.7% ($1,000 / $6,000), which falls well below the standard 25% maintenance margin requirement.

Margin Account vs. Cash Account: Key Differences

Understanding the structural differences between these two account types helps traders select the appropriate account structure for their trading goals.

Cash accounts require you to pay for all purchases in full by the settlement date. They suit long-term investors or risk-averse individuals who want to avoid borrowing costs and forced liquidations. Conversely, margin accounts provide greater capital efficiency, short-selling capabilities, and advanced order flexibility for active, experienced traders.

What Happens During a Margin Call?

A margin call occurs when your account equity falls below the broker's required maintenance margin threshold. When this happens, the broker issues a formal demand for you to restore the account to the minimum equity level.

When you get a margin call, you typically have two choices:

1. Deposit more cash, or add securities your broker accepts as collateral (called marginable securities).
2. Sell off existing positions to pay down the borrowed loan balance.

A lot of new traders assume their broker has to warn them first or wait a few days for a deposit before acting. That's not the case. In reality, brokerage agreements grant firms the legal right to liquidate open positions immediately without prior notification if market conditions threaten account solvency.

To manage downside market exposure before equity levels breach margin thresholds, disciplined traders often use risk control tools like a stop-limit order to help limit potential losses on leveraged positions. Keep in mind that a stop-limit order may not fill at all if the price gaps past your limit price, so it can't guarantee a capped loss.

Downside leverage accelerates losses just as effectively as it amplifies gains. If a stock purchased on 2:1 margin drops by 10%, your actual account equity drops by 20%, excluding accrued borrowing costs.

Common Margin Trading Mistakes to Avoid

Trading with borrowed money comes with a few common traps that can eat into your account fast if you're not careful.

• Maxing Out Available Buying Power: Using all of your available margin leaves you no cushion for normal price swings, which makes a margin call much more likely.
• Ignoring Cumulative Interest Charges: If you hold margin positions for weeks or months without counting daily interest in your profit math, borrowing costs can quietly eat away your gains.
• Failing to Monitor House Requirements: Don't assume your broker sticks to the 25% regulatory minimum. Firm-specific house requirements can be higher, and they can change during high-volatility events.

Conclusion

Trading on margin gives active traders enhanced purchasing power, short-selling access, and improved capital efficiency. However, these capabilities come with the ongoing cost of interest charges and the persistent risk of accelerated losses or forced liquidations.

Success with leverage requires strict capital management, a clear understanding of maintenance thresholds, and careful position sizing. If you're still building your overall market approach, working through our trading foundations guides and practicing proper cash management will give you the groundwork you need before adding margin leverage.