What is a margin call?
- A margin call demands more cash when your borrowed equity falls too low.
- It is triggered by a drop in the value of your margined holdings.
- Brokers give you a short window, often two to five days, to cover.
- Ignore it and the broker sells assets to restore the requirement.
- Margin calls arrive fast in volatile markets and can cascade into broad selloffs.
What is a margin call?
A margin call is a broker's demand to deposit more cash or securities into your margin account when your equity falls below the required minimum. It is a rule, not a suggestion. Ignore it and the broker sells your assets.
The call is a rule, not a suggestion. Brokers set a minimum equity ratio, and your account has to stay above it. When losses push you under, the broker issues the call to bring you back into line.
Why does a broker issue a margin call?
Because the broker's money is at stake. You borrowed part of the purchase price, and the loan is secured by your holdings. If the value falls far enough, the collateral no longer covers the debt. The broker calls you to restore that buffer before it gets dangerous.
The margin call is protection, but for the broker, not you. It keeps the lender whole by forcing you to top up while there is still room. If you cannot, the broker closes positions itself to recover the loan.
How is a margin call calculated?
Your broker compares what your holdings are worth to what you owe. Your equity is what is left over. Reg T needs a $2,000 minimum, and maintenance margin, typically 25% to 30%, is the floor the broker requires. Drop below it and a call goes out for the difference.
That difference is the amount you must add to return to the required level. The loan is not free, and interest on it grows your debt while you hold it. Every day the market moves, your equity moves with it.
What happens if you cannot cover it?
A broker seldom warns you first. If you do not deposit cash or securities in time, it sells assets from your account to bring equity above the requirement. The sale happens at market price, with no consultation and no regard for your plans.
That forced sale can lock in your worst loss. You sell at the bottom precisely because the bottom is what triggered the call. It is the cruelest part of margin: the moment that forces you out is the moment prices are weakest.
It is a feedback loop: prices fall, accounts get called, forced selling pushes prices lower. This is how margin cascades deepen selloffs. The forced sale of assets spreads the damage to other traders and markets.
You must act long before the broker's line is touched. Watch your equity daily. If a 10% drop would trigger a call, you are too close to the edge. Leave enough room that ordinary volatility shakes you, not empties you.
How do you avoid a margin call?
Borrow far less than your limit and keep a wide equity cushion. Set a personal stop level well above the broker's minimum, and honor it. The whole point is to act before the broker forces you to.
Stress-test your account for fast moves before you lever anything. Know exactly how far your equity can fall before the line is touched, and make sure the answer leaves you room to breathe.
Who sets the margin rules and why?
The rules come from above, not from your broker. The Federal Reserve sets the initial margin requirement under Regulation T, and FINRA sets the minimum maintenance level. Your broker can only demand more, never less.
The lesson is old and hard-won. Before the 1920s crash, traders could borrow up to 90% of a purchase, and when prices fell the calls went out in waves. The forced sales helped turn a decline into a disaster. Regulation tightened after that.
Most brokers hold you to maintenance around 25%, the FINRA minimum, though some demand 30%. That number is the equity floor for the whole account, and your broker may raise it for the riskiest stocks. Know the exact figure before you buy.
So the floor is set for you, and the only variable is your behavior. The rules protect the lender, not your account. Your defense is to act well before equity falls below the line, and treat two to five days as a gift, not a deadline.
What are the specific calls and timings you will hit?
Two different lines frame your exposure. Initial margin is the share of a purchase you must fund with your own cash, at least 50% for U.S. stocks, which caps your starting buying power around two to one. Maintenance margin is the lower floor you must hold afterward, typically about 25%.
A standard margin call comes when equity falls below the required maintenance level. A house call is a stricter demand from your brokerage, set above the exchange minimum, timed tighter. Short positions face the same call when prices rise against you.
Timing is the cruel part. You usually get two to five days to meet the call, but in a fast market a broker can act far sooner. If you do not cover it with cash or securities, the broker sells your assets without asking.
Price drops, equity falls below the line, and the forced sale of assets locks in the loss exactly when you could least afford it. That is why margin traders keep a cash buffer well beyond the broker's minimum.