A broker's own margin requirement, set above the exchange minimum for its own protection.
Exchanges publish a floor; brokers are free to charge more and frequently do — for volatile products, for concentrated accounts, or ahead of known events. They can raise it with little notice.
House requirements rising across the industry is itself a signal: it usually means the clearing firms expect a wide range and have stopped trusting their customers' risk management.
Example: before an election weekend a broker may double house margin on index futures from $15,000 to $30,000 per contract, forcing customers to halve size or deposit funds by Friday's close.
Original diagrams for the ideas on this page. Illustrative, not real market data.
Margin and leverage. A $5,000 deposit can control a $100,000 position, which is 20:1 leverage. Because the loss is measured on the full $100,000, a 2.5% move against you halves the deposit and brings a margin call, and a 5% move uses all of it.
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