You deposit $10,000, but the screen permits a $20,000 stock purchase. The extra buying power expands your market exposure without increasing your original money. If the stock falls, does the borrowing shrink with it?
Usually, the loan still must be repaid under its contract, and interest accrues. Put assets, debt, and net equity on the same page before asking whether you can wait for a price recovery. A cash demand may interrupt that wait.
Four amounts that are not all “my capital”
You will compare borrowed and unborrowed accounts under the same price changes, calculate gaps caused by interest and maintenance requirements, and distinguish buying power from household loss capacity.
Initial own funds are the money you contribute. Borrowing is a contractual liability. In our direct-stock example, notional exposure is the current total market value of the shares; do not extend that simplified definition to every complex contract. Account equity is stock and cash assets minus all accrued liabilities.
A margin account can provide a broker loan secured by account assets. A cash account requires full payment under its applicable rules. Borrowing increases buying power and can magnify losses, while generating interest charges.1 An account named “margin” does not itself show that you have borrowed. Check the actual loan balance rather than only the amount the platform permits you to buy.
Initial margin requirements constrain the own equity needed at purchase. Maintenance requirements constrain the equity required while holding the position. Margin is not an insurance premium that removes the remaining risk, and an initial contribution is not a guaranteed loss limit.
Give two accounts the same stock
This is C8-78, a separate synthetic dollar exercise. It changes none of Household A's renminbi assets, reserves, or strategy allowance. Both accounts buy the same fictional ordinary stock at $100. There are no other securities, dividends, external flows, or hidden cash. First exclude interest, fees, and forced liquidation to isolate the price effect; then examine those constraints separately.
A contributes $10,000 and buys 100 shares without borrowing. Assets and equity are both $10,000. B contributes the same $10,000, borrows another $10,000, and buys 200 shares. It has $20,000 of stock, $10,000 of debt, and still only $10,000 of equity. The loan creates no net wealth at purchase.
| Independent price scenario | A: stock value / equity | B: stock value | B: debt | B: equity | Gain or loss on original own funds |
|---|---|---|---|---|---|
| Start: $100 | $10,000 / $10,000 | $20,000 | $10,000 | $10,000 | Both 0% |
| Up 20%: $120 | $12,000 / $12,000 | $24,000 | $10,000 | $14,000 | A +20%; B +40% |
| Down 20%: $80 | $8,000 / $8,000 | $16,000 | $10,000 | $6,000 | A −20%; B −40% |
| Down 50%: $50 | $5,000 / $5,000 | $10,000 | $10,000 | $0 | A −50%; B −100% |
At $80, B's stock loses $4,000 while its debt stays unchanged. Equity falls to $6,000. Divide $6,000 by $16,000 of stock assets for an equity ratio of 37.5%. Divide the $4,000 loss by $10,000 of original own funds for a 40% loss. Each percentage answers a different question.
B's stock exposure divided by equity starts at 2. After the decline, $16,000 / $6,000 is about 2.67. It has bought no additional shares, yet exposure relative to remaining equity has grown. The initial multiple cannot describe the entire path, and “the stock fell only 20%” does not establish safety.
Unborrowed stock can also lose all its invested value. With fully paid direct holdings and no other obligations, however, the price decline alone does not create this financing margin call. The borrowed account can face a contractual action before its equity reaches zero.
Interest does not wait for a profitable month
Restart from B's original purchase for an independent interest scenario. Hold the $10,000 loan for one month at a synthetic 12% annual rate. The exercise uses simple interest, twelve equal months, no compounding or minimum charge, and adds accrued interest to debt. These are not a broker's current rate or day-count rules.
Interest is $100. Even with the stock unchanged at $100, assets of $20,000 minus accrued debt of $10,100 leave $9,900 equity. At a stock price of $80, assets of $16,000 leave $5,900 equity. The $4,100 loss is 41% of original own funds, one percentage point worse than the interest-free scenario.
Actual interest may accrue daily, vary over time, or involve different currencies and charges. Read the agreement. Paying interest outside the account does not remove its economic cost; it becomes an additional household cash outlay. Money contributed to repay borrowing is also an external flow, not investment profit.
A maintenance gap can appear before capital is exhausted
Every maintenance percentage below is a synthetic teaching condition, not a universal regulatory standard. Require equity to be at least 40% of current stock value. Any added outside cash immediately repays debt. Assume no other collateral or haircut rules. An actual account's calculations, security requirements, and disposal rights need their own investigation.
At the $80 price with accrued debt of $10,100, the $16,000 stock position requires $6,400 equity. Actual equity is $5,900, so the static gap is $500. Contribute $500 from outside and use it to repay debt: debt becomes $9,600 and equity becomes $6,400, just meeting this one condition.
That $500 is not cash already available inside the $5,900 equity. Nor is it an estimate of final loss or a promise against another call. Prices can fall, interest can accrue, or requirements can change. If the deposit uses money committed to household payments, the call creates a household funding conflict, not an exception to the earlier reserve policy.
Now consider a separate snapshot at a $90 stock price. Two hundred shares are worth $18,000. Accrued debt remains $10,100, so equity is $7,900, approximately 43.89% of assets. The 40% requirement is met. Raising it to 50% requires $9,000 equity and creates a $1,100 gap, even without another price decline.
Brokers can impose stricter house requirements and raise them. A customer may face a short response window or liquidation without advance notice.2 The example illustrates that mechanism; it does not predict when an actual account will receive a call or suggest that a 50% requirement creates safety.
Adding $500 and selling $500 do different things
Return to the $80 snapshot: stock $16,000, debt $10,100, equity $5,900, and the 40% requirement. Ignore sale fees and price movement to isolate the balance sheet.
Sell $500 of stock and use the proceeds to repay debt. Stock falls to $15,500 and debt to $9,600. Equity remains $5,900. Required equity is now $6,200, leaving a $300 gap. Selling and repaying reduces both assets and debt; it does not add outside equity.
To make $5,900 equal 40% of remaining stock value, stock must fall to $14,750. The simplified sale-and-repayment amount is therefore $1,250, not $500. This calculation assumes the precise fraction of shares can be sold. Actual liquidation quantities depend on prices, charges, trading units, and account rules.
You may not control which security is sold or how long the broker waits. FINRA describes forced sales, limits on notification and customer choice, and responsibility for a shortfall after sale.2 A plan that assumes “I will get a warning and choose what to sell” needs contractual support.
Update the later path too. Shares already sold cannot participate in a subsequent rebound. A simulation cannot remove financing pressure through liquidation while retaining the original 200 shares for future gains. Holdings and liabilities must remain on one consistent ledger.
A gap can cross the intended liquidation line
Forced liquidation is not loss insurance. Start another independent scenario with the original 200 shares at $100 and $10,000 loan, excluding interest. The next executable sale price is $40, with no intervening opportunity to trade. The exercise supplies complete liquidation there and a $50 liquidation-related charge.
Gross proceeds are $8,000, leaving $7,950 before repaying the loan. Against $10,000 owed, the shortfall is $2,050. Original own funds of $10,000 are exhausted, and $2,050 is still owed. Total wealth loss is $12,050, or 120.5% of the initial own funds.
The stock fell 60%, not 100%. A financed account can become negative without the security reaching zero. This is not a probability forecast or a claim that a real broker necessarily waits until $40. It shows how gaps, halts, or inadequate liquidity can prevent liquidation at an earlier reference price. A maintenance line cannot be presented as an executable maximum loss.
Several securities do not divide away the borrowing
Spreading $20,000 across five stocks changes security concentration, but leaves the same $10,000 debt. Joint declines and tighter collateral conditions can still create an account-wide gap. Selling one position may serve the entire account's funding requirement.
The household can face the same shock: reduced income, unchanged necessary payments, and a cash call at the least convenient time. G74's 30% or 50% stress-loss screen cannot simply be applied to a structure with obligations beyond initial funds. Recheck the contract, joint scenario, and confirmed cash sources; nominal margin is not an approved household risk budget.
The book's basic strategy path remains unborrowed, unlevered, and without short selling. Platform buying power does not change that scope. Even when buying a fund with cash, investigate whether the fund itself uses leverage. If final exposure and cash obligations remain unclear, do not insert the product into the basic allowance table as though they were known.
Recalculate a different funding mix
Explain. Why can a $10,000 contribution supporting $20,000 of stock not establish “my maximum loss is the $10,000 margin”? Address debt, execution, and outside cash.
Apply. In an independent snapshot, contribute $12,000, borrow $8,000, and buy 200 shares at $100. Price later becomes $75, and accrued interest is $200, making debt $8,200. There are no other fees. Maintenance rises from 40% to 50%, and added outside cash immediately repays debt. Calculate assets, equity, compliance at both percentages, and the new cash gap.
Compare an unborrowed account that instead buys 120 shares with its $12,000. It bears no financing interest and has not sold. Work through both before reading the answer.
Reference answers · reveal
Answer. The borrowed account has assets of $15,000 and equity of $6,800, approximately 45.33% of assets. The 40% requirement is $6,000 and is met. The 50% requirement is $7,500, leaving a $700 gap. Contributing $700 and repaying debt leaves $7,500 debt and $7,500 equity, exactly meeting the static condition without removing all future risk.
The unborrowed account has $9,000 equity, a $3,000 or 25% loss. The borrowed account loses $5,200, approximately 43.33% of its initial own funds, including $200 interest.
For the explanation, debt does not shrink automatically with the stock and can exceed liquidation proceeds. Forced sales have no fixed execution-price guarantee. Interest and extra deposits draw on household resources. “Leverage magnifies volatility” is incomplete without explaining how that becomes an actual payment obligation.
Save an assets, liabilities, and cash-obligations table
Keep a page for the original $80 snapshot and another for the $75 transfer. Record original own funds, shares and prices, assets, loan principal, accrued interest, equity, percentage denominators, the synthetic maintenance condition, outside contributions versus sale-and-repayment, and gaps under adverse or unavailable execution. List unknown real-contract fields and an unborrowed comparison.
Check that equity equals assets minus all accrued liabilities. Outside funding is not return. Liquidated shares cannot earn a later rebound. Every “shortfall” must identify whether it concerns a static maintenance requirement, an execution charge, or debt remaining after sale. One “margin” number cannot represent all three.
Assess leverage by tracing exposure, borrowing, and the cash obligations they create. Buying power answers how large an order may be permitted. A household risk budget asks which consequences can be borne. There is no reason for those answers to match automatically.
References
- Investor.gov: Investor Bulletin—Understanding Margin Accounts, June 10, 2021. Account types, loans, interest, equity, and losses beyond initial funds.
- FINRA: Margin Accounts, “Firm Practices,” “Know Before You Trade,” and agreements/disclosures. House requirements, liquidation rights, notification limits, and remaining shortfalls; no regulatory percentage or day-trading threshold is adopted here.
Editorial status
AI-assisted draft synchronized to the accepted second-round Chinese source. All prices, rates, maintenance percentages, and fees are independent synthetic teaching inputs. See the author review. A separate AI reviewer has completed an independent full-text and bilingual review. Human financial review and target-reader testing have not been performed and are not scheduled for this edition.