A margin call is not a market opinion, a polite reminder, or proof that a position is about to rebound. It is a balance-sheet event inside a leveraged account. Your broker has lent you money or allowed you to carry an obligation, the collateral supporting that exposure has become insufficient under the applicable margin rules, and the deficit must be corrected. If it is not, the broker can reduce the risk by liquidating positions—often without waiting for your permission.
That definition sounds simple. The mechanics are not. Traders routinely confuse initial margin with maintenance margin, assume a broker must give them time to respond, or calculate their risk from the position’s market value while ignoring the fixed loan underneath it. The result is a dangerous asymmetry: leverage makes gains on account equity look larger, but a falling asset does not reduce the debt at the same speed.
This guide explains the full chain: how margin accounts work, what triggers a call, how to calculate the critical price, why forced liquidation can require selling much more than the size of the deficit, and how the U.S. intraday margin changes that took effect in 2026 alter the framework for active traders. Data and rules are current as of August 22, 2026.
The short answer: what is a margin call?
A margin call occurs when the equity in a leveraged trading account falls below the minimum required by a broker, exchange, clearing venue, or regulator. Account equity is generally the market value of the assets minus the amount owed to the broker. To resolve the deficit, the trader may need to deposit cash, add eligible securities, close positions, or accept liquidation by the broker.
In a U.S. stock margin account, Federal Reserve Regulation T generally permits a broker to lend up to 50% of the purchase price of eligible securities at the time of purchase. After the trade, FINRA’s baseline maintenance requirement for long margin-eligible equities is generally 25% of current market value. Those percentages are floors, not promises. A brokerage firm can impose a higher “house” requirement—often 30% or 40%, and potentially much more for volatile, concentrated, low-priced, or illiquid securities.
The most important practical point is this: the broker protects its loan before it protects your investment thesis. A margin agreement can permit the firm to sell securities without consulting you, choose which positions to sell, raise house requirements, and deny an extension of time. A margin call may arrive as a notification, but liquidation rights do not depend on you answering the phone.
Margin is a loan, not extra capital
Suppose you buy $20,000 of stock with $10,000 of your own cash and a $10,000 margin loan. At the start:
- Market value of securities: $20,000
- Margin loan: $10,000
- Your account equity: $10,000
- Your equity percentage: 50%
If the stock rises 10%, the position becomes worth $22,000 while the loan remains approximately $10,000, before interest. Your equity rises to $12,000—a 20% gain on the $10,000 you supplied. That amplification is why leverage looks attractive.
If the stock falls 10%, the position becomes worth $18,000 but the loan is still $10,000. Equity falls to $8,000, a 20% loss on your capital. If the asset falls 50%, the position is worth $10,000 and your equity is effectively gone, while interest and execution costs may still leave a balance. Leverage does not change the asset’s return. It changes how that return is distributed between borrowed money and your much smaller equity cushion.
The three margin thresholds traders must separate
Minimum account equity
This is the minimum amount required before leveraged trading is available. In the U.S. securities framework, $2,000 remains a common regulatory minimum for using leverage in a margin account, although a firm can require more. An account may technically be labeled a margin account below that amount while still being restricted to unleveraged activity.
Initial margin
Initial margin determines how much equity is required when a position is opened. For many margin-eligible U.S. stocks, Regulation T’s general 50% requirement means a $20,000 purchase needs $10,000 of customer equity. Some securities are not marginable at all, and brokers may demand more than the regulatory baseline. Options, short sales, concentrated portfolios, and special-risk securities use different schedules.
Maintenance margin
Maintenance margin is the equity that must remain after the position is open. If the requirement is 30%, your equity must equal at least 30% of the current market value. This percentage is applied to a moving market value, while the margin loan is comparatively fixed. That interaction creates the call price.
Traders often remember the 25% FINRA baseline and treat it as universal. That is a mistake. The number on your broker’s platform is the one that controls your account in practice, and it may change quickly. During a volatility shock, a broker can raise the house requirement at the same moment the collateral is falling. A position can therefore approach a margin call through price, policy, or both.
The margin-call formula
For a simplified long stock position with one fixed margin loan, the logic is:
Account equity = market value − margin loan
A call begins when account equity falls below the required maintenance equity:
Market value − loan < maintenance rate × market value
Rearranging the equation gives the approximate call threshold:
Call market value = margin loan ÷ (1 − maintenance rate)
Return to the $20,000 position financed with a $10,000 loan. If the broker requires 30% maintenance margin:
$10,000 ÷ (1 − 0.30) = $14,285.71
The account reaches the threshold when the position’s market value falls to roughly $14,286. If the trader owns 100 shares purchased at $200, the corresponding price is approximately $142.86 per share. The stock has declined about 28.6%, but the trader’s equity has fallen from $10,000 to about $4,286—a loss of roughly 57.1% before interest and fees.
At a 40% house requirement, the same $10,000 loan creates a much higher threshold:
$10,000 ÷ (1 − 0.40) = $16,666.67
Now the call arrives near $166.67 per share, after a decline of only about 16.7%. This is why leverage cannot be assessed without the broker’s current house requirement.
Why a $1,000 deficit can require more than $1,000 of selling
Assume the position has fallen to $13,000 while the loan remains $10,000. Equity is $3,000. At a 30% maintenance requirement, required equity is $3,900, leaving a $900 deficit.
Depositing $900 of cash can cure that simplified deficit because it adds equity directly. Selling $900 of stock and using the proceeds to reduce the loan does not have the same effect on the equity ratio: both assets and debt fall by $900, so dollar equity remains $3,000 while the denominator becomes smaller.
To restore a 30% equity ratio through liquidation alone, the simplified sale amount is:
Required liquidation = deficit ÷ maintenance rate
In this example, $900 ÷ 0.30 equals $3,000. The broker may need to sell about $3,000 of securities and apply the proceeds to the loan. Real accounts can differ because they contain multiple positions, different margin treatments, unsettled trades, interest, option requirements, or price movement during execution. But the principle holds: the liquidation can be a multiple of the apparent deficiency.
What can trigger a margin call?
1. The collateral loses value
This is the familiar case. A leveraged long position declines, the loan stays in place, and equity shrinks. Overnight gaps are especially dangerous because a stop order cannot guarantee an execution price and the account can open below the calculated threshold.
2. The broker raises its house requirement
A broker may increase margin requirements for a single security or an entire class of positions. This often happens when volatility rises, liquidity deteriorates, an earnings event approaches, or a portfolio becomes concentrated. The market price does not need to move for available buying power to disappear.
3. Concentration increases
A diversified group of liquid securities may receive more favorable treatment than a portfolio dominated by one volatile name. If other positions are sold or lose eligibility, the remaining concentration can attract a higher requirement.
4. Interest and other debits accumulate
Margin interest increases the debit balance and reduces equity over time. Withdrawals, fees, short-sale charges, and certain distributions can also weaken the cushion. A flat position is not necessarily a static account.
5. A short position rises
A short seller borrows shares, sells them, and must eventually repurchase them. If the stock rises, the repurchase obligation grows. Unlike a long stock, whose price cannot fall below zero, a short position has no fixed maximum loss. Borrow fees can rise, and a hard-to-borrow security may be recalled or subjected to stricter house rules.
6. Options exposure changes nonlinearly
Long options are generally paid for in full, but short-option strategies can create substantial margin obligations. A move in the underlying, a volatility jump, assignment risk, or a change in time to expiration can increase the requirement rapidly. A spread that looks defined-risk on a payoff chart may still create operational stress if one leg is assigned while the other remains open.
Stocks, options, futures, and crypto do not use identical margin
In a stock account, margin is usually a loan secured by securities. In futures, margin is better understood as a performance bond. The trader posts initial margin, must remain above maintenance margin, and gains or losses are settled through daily mark-to-market. A futures margin call can therefore arise from adverse settlement variation even though the account did not borrow half the notional value in the Regulation T sense.
Options margin depends on strategy and broker methodology. Covered calls, cash-secured puts, defined-risk spreads, uncovered options, and portfolio-margin accounts can produce very different requirements. Portfolio margin is risk-based and may recognize offsets, but it can also respond sharply when modeled risk rises or correlations break.
Crypto exchanges and offshore derivatives venues use their own collateral, maintenance, and liquidation systems. Many display an estimated liquidation price, but that estimate can change with funding charges, fees, cross-margin exposure, collateral haircuts, and the venue’s mark-price methodology. The label “10× leverage” does not make one platform’s risk rules interchangeable with another’s.
The 2026 U.S. intraday margin change
FINRA’s new intraday margin requirements became effective on June 4, 2026, with a permitted transition period through October 20, 2027 for firms that need more time. The new framework replaces the old trade-count-based pattern day trader regime with a more risk-based approach. Once a firm transitions, there is no $25,000 day-trading minimum tied to a “pattern day trader” label; instead, the firm monitors whether the account has enough equity for its actual intraday positions.
If the account develops an intraday margin deficit, the firm expects it to be satisfied promptly. Repeated failure can lead to restrictions. During the transition, however, brokers may operate under different versions of the rules. A trader cannot safely infer the applicable system from the calendar alone. The broker’s implementation and account agreement remain decisive. We explain the timing, transition, and practical differences in our full guide to the 2026 U.S. intraday margin framework.
This change removes one famous threshold, but it does not remove margin risk. In some ways, real-time or end-of-day measurement of actual intraday exposure makes position-level discipline more important. A trader who avoids the old PDT designation can still create a deficit through leverage, options, concentration, or a fast price move.
How professionals think about margin risk
Use a stress price, not today’s buying power
Buying power answers how much the broker currently permits. It does not answer how much risk the account can survive. Before entering, calculate equity after a plausible gap, a volatility expansion, and a higher house requirement. For a volatile single stock, the relevant stress may be much larger than a normal daily move.
Keep distance from the threshold
A trader who plans to deposit money after a call is relying on bank-transfer timing, broker processing, and market liquidity during stress. Cash or unencumbered collateral already inside the account is more reliable. The buffer should be measured after considering other positions that are likely to fall at the same time.
Size the position from acceptable loss
Leverage should come after risk sizing, not before it. Define the invalidation point, estimate slippage, decide how much account equity can be lost, and calculate the position from those inputs. Our position sizing framework shows the arithmetic. If the broker offers more buying power than that calculation permits, the surplus is not a reason to enlarge the trade.
Know the firm’s liquidation sequence
Read the margin agreement and the broker’s risk disclosures. Determine whether the firm uses real-time liquidation, how it treats concentrated positions, whether alerts are informational rather than guaranteed, and which assets count as eligible collateral. Do not assume you will choose what gets sold.
Account for the cost of time
A margin-financed investment must earn more than the loan rate, taxes, and transaction costs merely to justify the financing. If the thesis requires years to play out, a variable borrowing rate and the possibility of forced liquidation can make a fundamentally sound asset unsuitable for leveraged ownership.
Five margin-call myths that cause real losses
- “The broker must call me first.” It may attempt to notify you, but the account agreement can permit liquidation without prior consultation.
- “I have until the stated deadline.” A deadline may be withdrawn if risk changes. Traders are generally not entitled to an extension.
- “The regulatory minimum is my requirement.” House requirements can be higher and can change.
- “A stop loss prevents a margin call.” Stops can gap, slip, be rejected, or execute after the account has already crossed a threshold.
- “Only losing positions will be sold.” The broker may liquidate whichever eligible assets most efficiently reduce its exposure, including profitable or long-term holdings.
A practical pre-trade checklist
- What is the current initial and maintenance requirement for this exact security or strategy?
- Can the requirement rise around earnings, expiration, or a volatility event?
- What market price creates a call under today’s rule?
- What price creates a call if the house requirement rises by ten percentage points?
- How much equity remains after an overnight gap beyond the planned exit?
- Are other positions exposed to the same factor, sector, or market shock?
- What interest, borrow fees, funding charges, or dividends will change the debit?
- Can the account meet a deficit with settled cash already available?
- Does the broker liquidate in real time, at the close, or under a hybrid process?
- Would the trade still make sense at lower leverage?
The bottom line
A margin call is the moment the broker’s collateral rules overtake the trader’s discretion. It can be triggered by a falling price, a rising house requirement, accumulated financing costs, nonlinear derivatives exposure, or several of these at once. The critical calculation is not simply how far the asset has fallen. It is how the market value, fixed debit, and maintenance percentage interact.
The cleanest defense is not faster reaction after the warning. It is a position that was designed to remain viable before the warning exists: lower gross exposure, a real liquidity buffer, explicit stress tests, and a risk limit based on account equity rather than available buying power. Margin is useful when it improves capital efficiency without giving the broker control of the exit. When the survival of a thesis depends on receiving a courteous phone call, the account is already carrying too much leverage.
