Margin Buying: Leveraged Long Positions
Margin trading involves borrowing capital from your broker, using your existing securities as collateral, to purchase additional assets. Under Regulation T of the Federal Reserve Board, the initial margin requirement for equities is currently set at 50%, meaning you can borrow up to half of the purchase price of a new position. FINRA mandates a maintenance margin requirement (typically 25% of the total market value of the account’s assets, though individual brokers frequently impose stricter “house” requirements of 30% to 40% depending on volatility).
Two things sit beside the Regulation T account. A portfolio margin account, available at most brokers above roughly $100,000 of equity under FINRA Rule 4210(g), replaces the fixed 50%/25% grid with a risk-based requirement computed by stressing the whole account across price scenarios, so a hedged or diversified book margins at a fraction of the strategy-based figure — more leverage on demand, and a call that arrives faster. And if the reason you are borrowing is to spend rather than to lever the portfolio, the instrument is usually a securities-backed line of credit at a bank rather than broker margin, priced off the same collateral but outside Regulation T entirely; section “Brokerage Firms and Rates” compares the two and section “Buy, Borrow, Die in Retirement” is the strategy built on them.
The mechanics of leverage are simple but unforgiving:
- Leveraged Compound Performance
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If you purchase $100,000 of equity using $50,000 of cash and $50,000 of margin debt, a 20% rise in the stock price increases the asset value to $120,000. After accounting for the debt, your equity is $70,000 — a 40% return on your capital (excluding interest costs).
- Leveraged Downside and Liquidation
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In the other direction, a 20% decline in the stock price reduces the asset value to $80,000. Your equity collapses to $30,000 — a 40% loss. If your equity falls below the maintenance threshold, the broker issues a margin call.
- The Margin Call
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When a margin call is triggered, you must immediately deposit cash or eligible collateral. On the position above — $50,000 of debt against 25% maintenance — the call arrives when the position’s value falls to , a 33% decline; under a 30% house requirement, $71,429, only 29% down. If you fail to deposit, or if the market moves too quickly, the broker has the legal right to liquidate your positions immediately without notice, at prevailing market prices, to protect their capital. This process forces you to realize losses at the absolute bottom of a cyclical drawdown.
Interest Rates and the Hurdle Rate Margin is not free. Brokers charge variable interest rates on margin debit balances, typically calculated daily and billed monthly. These rates are structured as a spread over a benchmark rate (such as the Secured Overnight Financing Rate, or SOFR). Because margin interest compounds, it establishes a steep hurdle rate that your investments must outperform just to break even. High-end brokers (like Interactive Brokers) charge low spreads over benchmark rates, whereas mainstream retail brokerages often charge usurious spreads of 3% to 6% above benchmark, making long-term margin holding economically destructive.
Tax Implications of Margin Interest The tax treatment of margin interest offers a valuable optimization opportunity under the Internal Revenue Code:
- Investment Interest Deduction
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Under IRC §163(d), “Investment Interest”, you can deduct investment interest expense (including margin interest), but only to the extent of your net investment income — interest, ordinary dividends, and short-term capital gains. You cannot use margin interest to offset salary or business income. Qualified dividends and long-term capital gains are excluded from net investment income by default; IRC §163(d)(4)(B) lets you elect to include them, but only at the price of taxing that income at ordinary rates instead of the preferential ones. That trade is almost never worth making — you are surrendering a 17-point rate spread to accelerate a deduction that would have carried forward anyway.
- Carryforward of Disallowed Interest
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Any excess investment interest that exceeds your net investment income cannot be deducted in the current tax year, but it can be carried forward indefinitely to offset future investment income.
- Wash Sale Rule
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The wash sale rule of IRC §1091, “Loss from wash sales of stock or securities” applies to margin accounts exactly as it does to cash accounts (see also IRS Pub. 550). If you liquidate a leveraged position at a loss and repurchase a substantially identical security within 30 days before or after the sale, the loss is disallowed and added to the basis of the replacement position.